richard g. carson b.sc, (wons) psychology, university of...

256
THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristol U.K., 1985 THESIS SUBTD IN PARTIAL W m N T OF THE REQUIREmWS FOR TEEi DEGREE OF MASTER OF SCIENCE in the School of KINESIOLOGY 0 RICHAm. G. CARSON 1988 SIMON FRASER UNIVERSm MAY, 1988 All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author*

Upload: others

Post on 17-Apr-2021

2 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

RICHARD G. CARSON

B.Sc, (Wons) Psychology, University of Bristol U.K., 1985

THESIS S U B T D IN PARTIAL W m N T OF THE REQUIREmWS FOR TEEi DEGREE OF

MASTER OF SCIENCE

in the School of

KINESIOLOGY

0 RICHAm. G. CARSON 1988 SIMON FRASER UNIVERSm

MAY, 1988

All rights reserved. This work may not be

reproduced in whole or in part, by photocopy or other means, without permission of the author*

Page 2: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

APPROVAL

NAME : Richard Carson

DEGREE : Master of Science (Kinesiology)

TITLE OF THESIS: The Asymmetrical Regulation of Pointing

Movements

Examining Committee:

Chairman: Dr. E.W. Banister

---CC--4---LY&x;----

Dr. D. Goodman Senior Supervisor

Dr. D. El iott McMaster University External Examiner

Date Approved F7 y,kd

Page 3: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

PARTIAL COPYRIGHT LICENSE

I hereby g r a n t t o Simon F r a s e r U n i v e r s i t y t h e r i g h t t o lend

my t h e s i s o r d i s s e r t a t i o n ( t h e t i t l e of which i s shown below) t o u s e r s

of t h e Simon F r a s e r U n i v e r s i t y L i b r a r y , and t o make p a r t i a l or s i n g l e

c o p i e s o n l y f o r . s u c h u s e r s o r i n r e s p o n s e t o a r e q u e s t from t h e l i b r a r y

of any o t h e r u n i v e r s i t y , o r o t h e r e d u c a t i o n a l i n s t i t u t i o n , on i t s 'own

b e h a l f o r f o r one of i t s u s e r s . I f u r t h e r a g r e e t h a t pe rmiss ion f o r

m u l t i p l e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d

by me o r t h e Dean of Graduate S t u d i e s . It i s unders tood t h a t copying

o r p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t b e a l lowed

wi thou t my w r i t t e n pe rmiss ion ,

Author : , L C - - C - , , ,

( s i g n a t u r e )

(name )

Page 4: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

ABSTRACT

Consideration was given to the way in which factors relating to the presumed

complexity of spatial processing required to locate a target in extrapersonal space, might

exert a consistent and asymmetrical effect upon the overt characteristics of pointing

movements. The role of ambient illumination in the regulation of such movements was also

examined. Target positions were never explicitly revealed but were indicated by brief,

linear, quadratic, cubic and quartic function, display sequences from which subjects were

required to extrapolate to the target location. Contrary to initial expectations, the complexity

of the pattern, indicating target position, had a symmetrical effect upon movement

parameters. Movements made by the preferred and non-preferred hands were, however,

observed to differ in terms of the Peak Velocity achieved during movement, and in terms of

movement duration. The pattern manipulation did however have consistent effects upon

Movement Time, F(3,21) = 11.18, p < 0.01, the Mean Peak Velocity, F(3,21) = 9.29, p

< 0.0005, and upon measures of Constant Error and Variable Error. Collectively these

indices may reflect the incidence of time consuming, modifications of the movement

trajectory.

The availability of ambient illumination during the execution of pointing was

associated with an increase in the absolute accuracy of responses relative to the non-

illuminated conditions, as expressed by Radial Error, F(l, 7) = 7.99, p < 0.05, even

though subjects were never afforded the opportunity for comparison of concurrent visual

information pertaining to limb and target positions. The manipulation of visual conditions

was not however associated with variations in Movement Time. Responses made by the

preferred and non-preferred hands did not differ with respect to the terminal accuracy of the

movement.

The results are discussed in terms of a vkety of "mechanisms" through which

visual information may be utilized in the regulation of goal directed action.

Page 5: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

ACKNOWLEDGEMENTS

The author wishes to express his gratitude to the Faculty and students in the School

of Kinesiology for their friendship and advice. My particular thanks are extended to the

support staff in the department, in particular Rob Taylor, and to George Mah, Dale Parkyn

and Paul Nagelkerke for the benefit of their expertise.

I am grateful to Dr. David Goodman for granting me the freedom and

encouragement to pursue lines of investigation which reflected personal philosophies and

interests, and to Dr. Arthur Chapman for his practical advice throughout.

Thanks also to Joe, Rekha, Tsily and Dario for their help, and numerous 'personal

communications'.

Page 6: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

DEDICATION

To my parents

HARRY AND MARY for their love,

and constant encouragement.

Page 7: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Heraclitus.. .says... that it is by something in motion that what is in motion is known; for he, like most philosophers, conceived all that exists to be in motion

ARISTOTLE

Page 8: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE OF CONTENTS

PREFACE .......................................................................................... 1

INTRODUCTION ................................................................................ -2

1.1 HISTORICAL ANTECEDENTS ................................................ 2

1.2 THE POSSIBLE ANATOMICAL BASES OF HEMISPHERIC DIFFERENTIATION .................................................................... 3

FUNCTIONAL ASYMMETRIES OF THE CEREBRAL HEMISPHERES .............. 6

2.1 CLINICAL STUDIES ............................................................ 6

2.2 EVIDENCE FROM ADDITIONAL SOURCES . SPLIT BRAIN STUDIES .................................................................................. 9

.............................. 2.3 ASYMMETRIES IN THE "NORMAL" BRAIN 11

THE NATURE OF HEMISFXERIC SPECIALIZATION ................................... 15

3.1 LOCAL AND GLOBAL MODELS .............................................. 15

3.2 THE ANALYTIC . HOLISTIC DICHOTOMY ................................ 17

3.3 SPATIAL VERSUS TEMPORAL? ............................................ -18

3.4 A RESTRAINED RESOLUTION ............................................... 20

HANDEDNESS AND CEREBRAL SPECIALIZATION .................................... 23

4.1 PREFERENCE AND PROFICIENCY ......................................... 23

................. 4.2 THE CONTRIBUTION OF DESCENDING PATHWAYS 25

................. 4.3 DEFICIENCIES IN THE "STRUCTURAL" APPROACH 27

AN "INDIRECT" APPROACH ................................................................. 29

5.1 THE SIGNIFICANCE OF THE STIMULUS INPUT ....................... 29

5.2 THE DUAL TASK PARADIGM ................................................ 31

5.3 APRAXIA AND RELATED DISORDERS .................................... 38

5.4 THE LEFT HEMISPHERE AS A "FEEDBACK PROCESSOR" .......... 39

CHARACTERISTICS OF THE MOTOR OUTPUT .......................................... 42

6.1 REASONS FOR CAUTION ..................................................... 42

6.2 TAPPING TASKS ................................................................ 42

vi i

Page 9: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

6.3 THE NON-ROLE OF ATTENTION ............................................ 47

.......... THE ROLE OF VISION IN THE REGULATION OF AIMED MOVEMENTS 53

7.1 A MINIMUM PROCESSING TIME FOR VISION? ......................... 53

7.2 THE MULTIDIMENSIONAL CONTRIBUTION OF VISION ............. 60

7.3 THE CONTRIBUTIONS OF CENTRAL AND PERIPHERAL VISION ................................................................................... -63

ASYMMETRIES OF RAPID AIMED MOVEMENTS ....................................... 66

8.1 THE ROLE OF FEEDBACK PROCESSING ................................. 66

8.2 THREE RECENT STUDIES ................................................... -68

THE SIGNIFICANCE OF SPATIALITY IN MOVEMENT ................................ 76

9.1 ARGUMENTS FOR ECOLOGICAL VALIDITY ............................. 76

9.2 CONVERGING EVIDENCE .................................................... 77

9.3 AN EVOLUTIONARY PERSPECTIVE ....................................... 79

EXPERIMENT 1 .................................................................................. 81

10.1 INTRODUCTION ................................................................. 81

10.2 METHODS ......................................................................... 85

SUBJECTS ....................................................................... 85

APPARATUS FOR DATA COLLECTION .................................. 85

MATERIALS .................................................................... -86

................................................................... PROCEDURE -88

10.3 RESULTS ......................................................................... -90

MEDIAN REACTION TIMES ................................................. 90

MEDIAN MOVEMENT TIMES ............................................... 94

10.4 DISCUSSION ..................................................................... 100

EXPERIMENT 2 .................................................................................. 103

INTRODUCTION ................................................................. 103

......................................................................... 11.2 METHODS 108

SUBJECTS ...................................................................... -108 viii

Page 10: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

APPARATUS FOR DATA COLLECTION .................................. 108

MATERIALS ..................................................................... 110

PROCEDURE .................................................................... 110

DATA REDUCTION ............................................................ 110

.......................................................................... 11.3 RESULTS 113

MEDIAN REACTION TIMES ................................................. 113

MEDIAN MOVEMENT TIMES ............................................... 116

RADIAL ERROR ................................................................ 122

X CONSTANT ERROR ........................................................ 126

Z CONSTANT ERROR ................................................. 133

X VARIABLE ERROR ......................................................... 138

Z VARIABLE ERROR .......................................................... 141

VARIABILITY IN THE TIME TO PEAK VELOCITY .................... 145

MEAN PEAK VELOCITIES ................................................... 147

11.4 DISCUSSION .................................................................... -157

SUMMARY AND CONCLUSIONS .......................................................... -170

12.1 SUMMARY OF RESULTS ...................................................... 170

12.2 CONCLUDING REMARKS ................................................... -171

APPENDIX A ..................................................................................... -175

APPENDIX B ...................................................................................... 176

APPENDIX C ...................................................................................... 177

APPENDIX D ..................................................................................... -182

REFERENCE NOTES ............................................................................ 219

REFERENCES ................................................................................... -220

Page 11: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

LIST OF TABLES

Table Page

10.1 Median Reaction Time (ms) as a Function of Hand and Visual Field ................ 90 10.2 Median Reaction Time (ms) as a Function of Hand and Pattern ...................... 92 10.3 Median Movement Time (ms) as a Function of Hand and Visual Field .............. 94 10.4 Median Movement Time (ms) as a Function of Hand and Pattern .................... 96

.......................... 10.4b Median Movement Times (ms) Differences among Means 96

10.5 Median Movement Time (ms) as a Function of Hand and Relation to ....................................................................................... Midpoint -97

10.6 Median Movement Time (ms) as a Function of Hand. Visual Field and Target . . .................................................................................... Eccentricity -98

11.1 Median Reaction Time (ms) as a Function of Hand and Visual Field ................ 113 1 1.2 Median Reaction Time (ms) as a Function of Hand and Pattern ...................... 114

1 1.3 Median Movement Time (ms) as a Function of Hand and Visual Field .............. 116 .................... 11.4 Median Movement Time (ms) as aFunction of Hand and Pattern 118

11.4b Median Movement Time (ms) Differences among Pattern Means ................... 118 11.5 Median Movement Time (ms) as a Function of Hand and Relation to

....................................................................................... Midpoint -120

11.6 Radial Error (mm) as a Function of Hand and Visual Condition ...................... 122 11.7 Radial Error (mm) as a Function of Hand. Visual Field and Relation to

....................................................................................... Midpoint -124

1 1.8 X Constant Error (mm) as a Function of Hand, Visual Condition and Visual ............................................................................................ Field -126

11.9 X Constant Error (rnm) as a Function of Visual Field. Relation to Midpoint . . and Target Eccentricity ........................................................................ 127 11.10 X Constant Error (mm) as a Function of Pattern. Relation to Midpoint and

............................................................................ Target Eccentricity -130

1 1 . lob X Constant Error (mm) Differences among Pattern Means ......................... 131 1 1.1 1 Z Constant Error (mm) as a Function of Hand and Visual Condition ............... 133 11.12 Z Constant Error (mm) as a Function of Hand. Visual Field and Pattern .......... 134 11.13 Z Constant Error (mm) as a Function of Pattern. and Relation to Midpoint ........ 136

X

Page 12: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

1 1.14 X Variable Error (mm) as a Function of Hand, Visual Condition and Visual Field ............................................................................................ -138

1 1.15 X Variable Error (mm) as a Function of Visual Field and Pattern ................... 139

11.15b X Variable Error (rnm) Differences among Pattern Means .......................... 140

1 1.16 Z Variable Error (mm) as a Function of Hand. Visual Condition and Visual Field ............................................................................................ -141

11.17 Z Variable Error (mm) as a Function of Visual Condition and Pattern .............. 143

.......................... 1 1.17b Z Variable Error (mm) Differences among Pattern Means 143

11.18 Variability in the Time to Peak Velocity as a Function of Hand and Visual Field ............................................................................................ -146

1 1.19 Mean Peak Velocity ( d s ) as a Function of Hand. Visual Condition and Visual Field ................................................................................... -147

1 1.20 Mean Peak Velocity (m/s) as a Function of Hand and Visual Field ................. 148

11.21 Mean Peak Velocity ( d s ) as a Function of Visual Condition and Visual Field ............................................................................................ -149

........ 11.22 Mean Peak Velocity ( d s ) as a Function of Pattern and Target Eccentricity 150

1 1.22b Mean Peak Velocity (ds). Differences among Pattern Means ..................... 150

..... 1 1.23 Mean Peak Velocity ( d s ) as a Function of Pattern and Relation to Midpoint 152

1 1.24 Mean Peak Velocity ( d s ) as a Function of Hand, Visual Field and Target . . Eccentricity. ................................................................................... -153

11.25 Mean Peak Velocity ( d s ) as a Function of Hand, Visual Condition and Pattern ......................................................................................... -155

1A Mean Number of Zero Crossings as a Function of Hand and Pattern .................. 178

............... 1.1A Mean Number of Zero Crossings. Differences among Pattern Means 178

......... 2A Number of Zero Crossings as a Function of Hand and Relation to Midpoint 180

3A Number of Zero Crossings as a Function of Visual Condition. Visual Field and Relation to Midpoint. ........................................................................ -181

Page 13: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

LIST OF FIGURES

Figure Page

10A Schematic representation of the position of the subject relative to the display ........................................................................................... panel -86

...................................... 10.1 Median Reaction Time (ms) Hand by Visual Field 91

............................................ 10.2 Median Reaction Time (ms) Hand by Pattern 92

.................................... 10.3 Median Movement Time (ms) Hand by Visual Field 95

.......................................... 10.4 Median Movement Time (ms) Hand by Pattern 97

.......................... 10.5 Median Movement Time (ms) Hand by Relation to Midpoint 198

10.6 Median Movement Time (ms) Hand by Visual Field and Target Eccentricity ....... 99

................................ 1 1.1 Median Reaction Times (ms) by Hand and Visual Field 114

...................................... 1 1.2 Median Reaction Times (ms) by Hand and Pattern 115

1 1.3 Median Movement Times (ms) by Hand and Visual Field .............................. 117

1 1.4 Median Movement Times (ms) by Hand and Pattern ................................. 119

.................... 11.5 Median Movement Times (ms) by Hand and Relation to Midpoint 120

....................................... 1 1.6 Radial Error(mm) by Hand and Visual Condition 123

................... 1 1.7 Radial Enor(rnm) by Hand. Visual Field and Relation to Midpoint 124

.................... 11.8 X Constant Error (mm) by Visual Field and Relation to Midpoint 128

....................... 11.9 X Constant Error (mm) by Visual Field and Target Eccentricity 128

11.10 X Constant Error (mm) by Visual Field. Relation to Midpoint and Target . . .................................................................................... Eccentricity -129

1 1.11 X Constant Error (mm) by Pattern and Relation to Midpoint ........................ 131

11.12 X Constant Error(mrn) by Pattern. Relation to Midpoint and Target . . .................................................................................... Eccentricity -132

................................... 1 1.13 Z Constant Error(mm) by Visual Field and Pattern 135

........................... 1 1.14 Z Constant Error (mm) Hand by Visual Field and Pattern 135

......................... 1 1.15 Z Constant Error(rnrn) Pattern . by Relationship to Midpoint 137

11.16 X Variable Error(mm) Hand by Visual Condition ..................................... 139

....................................... 1 1.17 X Variable Error (mm) Visual Field By Pattern 140 xii

Page 14: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

1 1.18 Z Variable Error(mm) Bind by Visual Field ........................................... 142

11.19 Z Variable Error (mm) Visual Condition by Pattem ................................... 144

11.20 Variability in the Time to Peak Velocity as a Function of Hand and Visual Condition ...................................................................................... -145

11.21 Variability in the Time to Peak Velocity as a Function of Hand and Visual Field ............................................................................................ -146

1 1.22 Mean Peak Velocity (m/s) as a Function of Hand and Visual Field ................. 148

1 1.23 Mean Peak Velocity ( d s ) as a Function of Visual Condition and Visual ............................................................................................. Field 149

1 1.24 Mean Peak Velocity (m/s) as a Function of Pattern and Target Eccentricity ........ 151

..... 1 1.25 Mean Peak Velocity (m/s) as a Function of Pattern and Relation to Midpoint 152

1 1.26 Mean Peak Velocity (m/s) as a Function of Hand. Visual Field and Target . . Eccentricity. ................................................................................... -154

1 1.27 Mean Peak Velocity (m/s) as a Function of Hand, Visual Condition and Pattern .......................................................................................... 156

.................................. 1A Mean Number of Zero Crossings by Hand and Pattern 179

2A Mean Number of Zero Crossings by Hand and Relation to Midpoint ................... 180

3A Mean Number of Zero Crossings by Visual Condition. Visual Field and Relation to Midpoint .......................................................................... 182

... X l l l

Page 15: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

PREFACE

In recent years a large number of studies have been conducted with the apparent aim

of clarifying the mechanisms which give rise to the almost universal superiority of the

'preferred hand' on a variety of manual tasks and in particular aimed movements. It has

been customary to link exhibited manual asymmetries, at least in part, to the presumed

processing characteristics of the cerebral hemispheres. This paper examines in some detail

the historical, theoretical and experimental background to this approach and highlights

ways in which apparently conflicting accounts may be reconciled. Consideration is also

given to the manner in which visual infoxmation is used in the regulation of such

movements, and the implications this may have for the examination of manual

asymmetries.

Page 16: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 1

INTRODUCTION

1.1 HISTORICAL ANTECEDENTS

Throughout the modern history of the "Mind's Sciences" there have been recurring

attempts to establish specificity of neural functions. These can be clearly discerned in the

writing of Descartes who was among the f ~ s t to recognize that different bodily functions

were subject to control exerted by various regions of the brain.

Perhaps the most infamous proponent of localization was the German anatomist

Franz Gall, whose writings, in the hands of his most ardent followers were expressed in

the doctrine of phrenology. It is of little surprise that Gall's own extreme view, that an

individual's intellectual and emotional profile could be revealed by examination of the

unique configuration of his or her skull, was dismissed in serious scientific circles.

Nonetheless, there was at least some merit in his claim that the faculty for speech was

located in the most anterior parts of the cerebral cortex, the frontal lobes. It was to be some

time however before there would appear evidence that would provide some limited support

for this notion.

The most obvious attempts to establish localization of neural function have been

along the lines of the physical demarcation of the left and right cerebral hemispheres. It has

variously been suggested (e.g., Boring, 1950; Gardner, 1985) that, the presumed,

specialization of the cerebral hemispheres for particular functions was articulated first by

the French surgeon Paul Broca in the early 1860's (Broca 1861), although the conclusion

that speech is controlled by the left hemisphere had been drawn almost thirty years prior to

Broca's presentation. A French country doctor, Marc Dax had in 1836 presented data

demonstrating that aphasia was accompanied by left hemisphere damage, yet his conclusion

that speech is controlled by the left half of the brain was seemingly overlooked. It was

however Broca who compiled evidence of a good deal more substantial nature, including

comprehensive details of case histories and circumscribed anatomical damage.

John Hughlings Jackson's proposal in 1868 of a "leading hemisphere" was itself a

reflection of merely five years of coordinated clinical research during which the concept of

cerebral dominance had already crystallized. There rapidly developed a widely held view of

hemispheric disparity, as Jackson (1958) concludes "that in most people the left side of the

brain is the leading side - the side of the so called will, and that the right is the automatic

side".

Page 17: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

The conviction that the right hemisphere was essentially the minor hemisphere was

compounded by evidence revealing difficulties in understanding speech, created by damage

to the rear of the temporal lobe in the left hemisphere (Wernicke, 1874), and by the

catalogued loss of reading comprehension and writing which followed unilateral left

hemisphere damage. In contrast, even large scale damage to the right hemisphere appeared

to have negligible effect upon language functions. In spite of occasional proposals that the

right hemisphere could to some extent compensate for left hemisphere damage (e.g.,

Dejerine & Thomas, 1912; Goldstein, 1917), and that the right hemisphere might even

possess capabilities of its own (Jackson, 1865), there was general adherence to the notion

of strict dominance. It has only been in the second half of this century that this

conceptualization of hemispheric asymmetry has been reassessed

1.2 1 DIFFERENTIATION

The view that cerebral dominance may arise as a consequence of anatomical

asymmetries is a venerable one, nevertheless, in spite of a body of data indicating some

differences between the hemispheres in specific regions (e.g., Connolly, 1950; Pfeifer,

1936; Von Economo & Horn, 1930), the standard view of cerebral dominance for

language, throughout the greater part of this century, was that it possessed no anatomical

correlate, had no analogue in other species and that its evolution in man was not amenable

to study (Damasio & Geschwind, 1984). The accepted view was most lucidly expressed by

von Bonin in his 1962 review, in which, although justifiably dismissing as unimportant

asymmetries such as mass, specific gravity, surface area or length von Bonin displayed a

corresponding disregard for those studies which had already revealed specific structural

differences between the hemispheres. It was in this climate that Geschwind and Levitsky

(1968) published what was to become a seminal report demonstrating, unequivocally, the

existence of asymmetries in the brain regions thought to be important for speech and

language, specifically, in the temporal plane. A number of subsequent studies, using a

variety of procedures, have confirmed the presence of distinct differences between the

temporal planes (e.g., Wada, Clark & Hamin, 1975; Witelson & Paillie, 1973).

Although the magnitude of the asymmetries was impressive, of potentially greater

importance was the observation that virtually all involved the Sylvian fissure or structures

within or along its banks (Geschwind, 1974). This structure is not found in non primate

mammals and indeed has changed considerably in the course of evolution (Connolly,

1950). It is in the region of the Sylvian fissure that are found the major speech areas such

as those of Broca and Wernicke, these are the areas in which lesions are found in most 3

Page 18: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

cases of severe aphasia. Geschwind and Levitsky (1968) demonstrated the presence of

structural between hemisphere differences in the Sylvian fissure, leading Geschwind

(1974) to the conclusion that particular cortical areas, all intimately related to speech

function, were larger in the left hemisphere. This appeared to provide at least some initial

confirmation that some manifestations of dominance may arise from physiological

mechanisms. It has also been noted that, in right handers, the right occipital cortex appears

to be of larger size (McRae, Branch & Milner, 1968), these and other posterior regions,

which may be slightly larger in the right hemisphere, are the areas which have been

independently assessed to be most critically involved in visuospatial operations (Harris,

1978).

Indeed, in the past decade, the application of sophisticated techniques has permitted

examination of asymmetries at the microscopic level. Post mortem examinations have

revealed that in the auditory association cortex, a region involved in high level processing

of auditory information and in particular speech, there exist anatomically distinct cell layers,

referred to as Tpt, which are larger in the left hemisphere (Galaburda, Sanides and

Geschwind, 1978). Similarly, cell layers types lying between the temporal and parietal

lobes, PG, appear to be larger on the left side of the brain (Galaburda & Sanides, 1980).

There does then appear to be at least some linkage between asymmetries at the macroscopic

and microscopic levels, enlarged areas of Tpt and PG cells have been correlated with the

size of the temporal plane (Springer & Deutsch, 1985).

Recent research has also provided some substantiation for claims regarding the

presence of neurochemical asymmetries in the brain. In a fashion consistent with

indications from gross anatomical studies, the primary differences have been found in those

areas associated with language processing, for example, the neurotransmitter

norepinephrine appears to be distributed unequally on each side of the thalamus (Ode,

Keller, Mefford and Adams, 1978). Additionally there appear to exist neurochemical

asymmetries at the cortical level, enzymes associated with the activity of the

neurotransmitter acetylcholine, in particular choline-acetyl-transferase (CAT), demonstrate

greater activity in the left than the right temporal lobe, again an area thought to be intimately

associated with the facility for language (Amaducci, Sorbi, Albanese & Gainotti, 198 1).

There is additional evidence, obtained from the "living brain" using techniques such as

cerebral angiography (LeMay & Culebras, 1972) and computerized tomography (CT scan)

(LeMay & Geschwind, 1978), which is consistent with the asymmetries found in post

mortem examinations.

There are, however, a number of problems associated with the evaluation of

anatomical asymmetries, not least in interpreting these differences in a manner which is 4

Page 19: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

meaningfully related to functional asymmetries. The clinical value of these insights is

undisputed, in addition the illustration that cerebral dominance has potentionally some

anatomical correlate gives some scope for considering the biological basis of hemispheric

differentiation. Nevertheless, as Springer and Deutsch (1985) point out, "ultimately it is

likely that dividing the brain in terms of 'where' will not completely answer the question of

'how' " (p. 115). It is to studies examining functional asymmetries of the cerebral

hemispheres to which one must turn in order to elucidate the role of the so called minor

hemisphere.

Page 20: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 2

FUNCTIONAL ASYMMETRIES OF THE CEREBRAL HEMISPHERES.

2.1 CLINICAL STUDIES

As outlined, the concept of cerebral dominance arose initially from observations of

the frequent relationship of aphasia and damage to the left cerebral hemisphere in right

handers. However, with the disclosure of multiple functional asymmetries which favour

the right rather than the left hemisphere, the notion of a major and minor hemisphere has

come to be reassessed (Weinstein, 1978). The rationale for clinical examination of

functional asymmetries is loosely described as follows, if individuals suffering damage to a

given hemisphere perform more poorly on a task than individuals with disruption limited to

the other side of the brain, the "mental abilities" for the task can be considered to dwell

primarily in the former hemisphere (Nebes, 1978). The problems of this approach will

soon become evident, although the examination of clinical cases has, however, proved

provocative if inconclusive.

The term aphasia has come to encompass a wide range of speech and language

disorders arising from a broad spectrum of, predominantly left hemisphere, neurological

damage. With the introduction of analytic techniques of increasing subtlety, it has become

clear that the right hemisphere plays a complimentary role in linguistic communication. The

right cerebral hemisphere appears not only to comprehend language in a manner which was

not previously contemplated, but may subserve the processing of nuances of speech such

as intonation and aspects of metaphor (Springer and Deutsch, 1985). A number of aphasics

with intact right hemispheres can derive the meaning of received speech (Danly & Shapiro,

1982), whilst individuals with right hemisphere damage often exhibit speech absent of

intonation (Heilman, Scholes & Watson, 1975).

It is however, with respect to "non-verbal" abilities that the contribution of the right

hemisphere appears most profound. There are aspects of musical processing for which the

right hemisphere seems particularly well equipped, for example; tonal memory, timbre,

melody recognition and intensity (Springer and Deutsch, 1985), and the capacity for

singing appears to remain in patients having undergone a complete left hemispherectomy

(Smith, 1966; Zaidel, 1973). Heilman, Scholes and Watson (1975) have suggested a

leading role for the right hemisphere in the processing of emotional information, whilst a number of studies have indicated that astereognostic conditions occur with greatest

frequency in patients who have suffered lesions in the area of the right parietal lobe (De

Renzi, Faglioni & Scotti, 1970; Fontenot & Benton, 1971). Astereognosis is characterized 6

Page 21: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

by a loss of awareness of the spatial relations of ones's body parts or "body scheme" (Ban & Kiernan, 1983). Furthermore, such patients often experience interference with tactile-

kinesthetic memories and are unable to recognize familiar objects when using only tactile

cues (Springer & Deutsch, 1985).

Indeed it is patterns of.performance on what might liberally be classified as "spatial"

tasks which appear to indicate the wider significance of right hemisphere functioning. As

Benton (1969) points out, one of the most dramatic effects upon overt behaviour, in a

patient more usually suffering damage to the right side of the brain, is disruption of the

facility to percieve and manipulate the spatial relationships of objects, both in relation to

himself and to one another. Individuals may be unable to reproduce structures organized in

space and may become lost, unsure of their orientation in an otherwise familiar locale

(Nebes, 1978). Similarly striking is the phenomenon of unilateral neglect. Generally

observed in patients having suffered large scale disruption of the right posterior occipital

regions, the victim will act as if the entire left side of space, and on occasions the left side

of their own body, does not exist (Springer & Deutsch, 1985).

Although the precise distribution of spatial "abilities" between hemispheres remains

unclear, the right hemisphere percept appears to predominate at the primary level of line

orientation and direction of movement (Nebes, 1978; Warrington & Rabin, 1970). The

transition from consideration of the right hemisphere as minor to a view which considers

each side of the cortex as equivalent in importance evolved simultaneously with the

appreciation that the:

ability to scan extrapersonal space and locate stimuli with respect to one another and in relation to the observer mav be considered a ~rereauisite of every operation implying spatial and cognition (be ~ i n z i , 1978, p. 53).

This shift has been accompanied by a large and still expanding body of clinical

evidence demonstrating the importance of the right hemisphere in the mediation of a

number of spatial tasks. The ability to infer the organization and structure of the external

environment without recourse to detailed analysis of the sensory array, generating a percept

of the whole from fragmentary information, is viewed as an essentially spatial function

(Nebes, 1978), and following Thurstone (1944), "closure speed" is the rapidity with which

this operation may be accomplished. Right hemisphere damage appears to detrimentally

affect closure speed to a greater extent than left hemisphere damage @e Renzi & Spinnler,

1966; Lansdell, 1968). Individuals having sustained right posterior or parietal damage

demonstrate problems with spatial orientation and construction (Critchley, 1953; De Renzi,

1967; Patterson & Zangwill, 1944, McFie & Piercy, 1952), whilst deficiency pattern

Page 22: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

recognition has resulted from lesions of the right temporal lobe (I(lmura, 1963; Lansdell,

1961, 1968; Meier & French, 1965; Milner, 1958). De Renzi (1978) has suggested that

there may exist a "supramodal mechanism guiding the sensorimotor neuronal networks

involved in scanning extrapersonal space through the various modalities" (p. 58).

Certainly, it appears that disorders of space perception are not restricted to the visual

modality, but occur in both auditorily and tactually guided tasks. Milner and Teuber (1968)

also recount that individuals with right temporal lobectomies did significantly poorer than

controls, and those with equivalent left side operations, on maze learning tasks. The same

pattern of results has been observed on a number of intelligence test subscales. Right

hemispherectomized patients do less well on the Block Design subtest of the Wechsler

Intelligence Test (Smith, 1969; Gott, 1973a) and when dealing with the geometrical figures

comprising the Raven's Coloured Progressive Matrices (Smith, 1969). Additionally, Kohn

and Dennis (1974) have independently confirmed that hemispherectomized patients with

intact right hemispheres perform more efficiently on spatial tasks than those possessing

only a left hemisphere. Patients with right hemisphere disease have also been observed to

perform more poorly than those with equivalent left hemisphere damage tasks involving;

recognition of abstract figures (Rubino, 1970), recognition of overlapping figures (De

Renzi et al, 1969; Gainotti & Tiacci, 1971), the matching of fragmented circles (Meier &

French, 1965) and the detection of a depth effect arising from the presentation of random

dot stereograms (Cannon & Bechtoldt, 1969; Benton & Hecaen, 1970).

The balance of clinical data appears initially to give lie to the notion of cerebral

dominance. As Nebes (1978, p. 120) concludes

when required to perform a spatial transformation on sensory input ..., the minor hemisphere is far superior to the major. This suggests that in man the right cerebral cortex is responsible for forming from the incomplete information provided by our senses the spatial and cognitive map of our surroundings in which the planning and organization of behaviour take place.

There are obviously likely to exist a number of potentially confounding variables of which

one must take account in any comparison between individuals suffering left or right

hemisphere disruption. Groups of patients should be matched for size and locus of

damage, and additionally upon dimensions such as age, sex, education and premorbid

intelligence (Nebes, 1978). The damage sustained is rarely well circumscribed and often

does not respect what are regarded as anatomical boundaries. This is also characteristic of

surgically inscribed lesions performed for medical reasons, and poses obstacles in the path

of attempts to establish whether there exists regional or focal representation of function

within a hemisphere. As Springer and Deutsch (1985) highlight, damage may be sustained 8

Page 23: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

to areas directly subserving a given function, or to areas anatomically distinct but

functionally related, resulting in equivalent decrements in either instance. The behaviour

exhibited by an individual subsequent to trauma reflects the functioning of the remaining

brain tissue. With direct reference to the two sides of the brain, overt behaviour may result

from depressed performance of the damaged hemisphere, or from the undisrupted, but

initially inferior, activity of the intact hemisphere (Nebes, 1978). Indeed, diaschisis may

occur, the undamaged hemisphere operating more poorly as a consequence of damage to

the other side of the brain. Clearly, considerable caution should be exercised in the

unfettered interpretation of clinical data.

2.2 EVIDENCE FROM ADDITIONAL SOURCES - SPLIT BRAIN STUDIES.

Clinical evidence of the asymmetrical functioning of the cerebral hemispheres did

not remain uncorroborated, a major impetus towards rationalization of these strands of

belief was provided by what have become popularly known as the "Split Brain Studies".

Until even the late 1930's there was considerable debate as to the role sustained by

the commissural fibre tract, the corpus callosum, it might intuitively have been supposed

that the corpus callosum and other connecting commissures and subcortical connections

would serve some integrative function, yet evidence that this was the case was notably

absent. The only certain role appeared to be that the fibres aided the spread of epileptic

discharge from one side of the brain to the other (Erickson, 1940; Van Wagenen & Herren,

1940). Indeed, these observations merely provided fuel for the facetiae of commentators

such as McCullough (1940) who perhaps doubted the evolutionary utility of a structure

which accentuated the symptoms of localized seizures. In a similar vein, it was with some

irony that Lashley (1950) proposed that the major role of the corpus callosum was to "keep

the hemispheres from sagging" and was thus largely mechanical.

There did however prove to be some utility in the observations of this single

functional attribute. After an initial series of largely unsuccessful operations, complete

cornmissurotomies (the severing of all the fibres of the corpus callosum) appeared to be

successful in limiting the consequences of seizure activity in what were regarded as intractable epileptics. The medical benefits appeared initially to be bereft of accompanying

post surgical deficits (Akelaitis, 1941, 1944), however more extensive and ingeneous

testing orchestrated by Roger Sperry (c.f., Sperry, 1982) demonstrated that, under specific

conditions, the commissurotomized patients were severely limited in their abilities to

perform tasks which necessitated the performance of one hemisphere in isolation from the

other.

Page 24: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

These patients appeared to be able to conduct their everyday lives in a conventional

fashion, as both hemispheres receive common information across all modalities even in the

absence of interhemispheric communication. For example the optic chiasm remains intact,

and thus, each hemisphere generally receives portions of the same visual image, if however

visual information is presented solely to one visual field by way of a brief, spatially

localized, exposure, in the absence of eye movement, the stimulus will be projected to the

opposite hemisphere. The perfoxmance of the individual hemisphere may subsequently be

examined in relative isolation.

Research on cornmissurotomized patients has provided confirmation of clinical

evaluations indicating that speech, for the majority of individuals, is the perogative of the

left hemisphere, yet again,the right hemisphere has not been seen to be without language

capabilities, a considerable degree of comprehension has been observed (e.g., Zaidel,

1978). In general however, the right hemisphere has again been observed to demonstrate a

specialization for what are complex, often non linguistic, visual and spatial processes.

Indeed, the right hemisphere has been found to be a good deal more proficient on a

varied selection of spatial and drawing tasks. This right hemisphere advantage appears to

be present at what, from an information processing perspective, might be considered as

relatively fundamental stages of processing. Durnford and Kimura (197 1) observed a right

hemisphere superiority for binocular depth perception, whilst Trevarthen and Leby (1973)

found an accompanying advantage for the detection of motion and the orientation of lines,

arrows and two dimensional objects located in space. A number of studies have concerned

themselves with potential differences in the transmodal transformations required to match

figures to the objects they represent. The left hand performs better when matching wooden

blocks to 2-dimensional drawings of the block in "opened up" form (Levy-Agresti &

Sperry, 1968), and when assembling coloured blocks to match a design (Gazzaniga,

1970). This superiority of the right hemisphere appears to increase as shapes become less

geometric and more free form (Franco & Sperry, 1977). Likewise, Nebes (1971) has

shown that the "left hand system" is superior in establishing the relationship between an arc

and the circle from which it came. This differential ability to establish the whole from its

parts was further emphasized using dot stimulus arrays (Nebes 1973) and line drawings

(Nebes 1972). Constructive reproduction in solving visuospatial problems has also been

examined by Bogen and Gazzaniga (1965) and by Levy (see Sperry, 1974), in the latter

case, a qualitative difference was observed, right hand performance was accompanied by a

running verbal commentary and appeared to be more hesitant. Furthermore, the left hand,

in split brain individuals, has been found to be more proficient when producing geometric

and perspective drawings (Bogen, 1969). 10

Page 25: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Although the conclusions drawn from research conducted with commissurotomized

patients do appear to be in substantial agreement with those obtained from clinical studies,

specifically that the right hemisphere may better assimilate space relations and

configurations of object form, and perform part-whole transformations (Trevarthen, 1974),

it is also prudent to articulate some widely held reservations.It is certainly the case that

information may be transferred from one half of the brain to the other by commissures

situated in lower regions, commissurotomy severs only those nerve fibres lying in the

cortex leaving most subcortical structures intact. Structures such as the superior colliculus,

lying subcortically, are important in their own right. This structure has been implicated in

visual processing, in particular with regard to the spatial locii of stimuli. The commissures

connecting the left and right superior colliculi are not intruded upon by commissurotomy,

thus, irrespective of the position in the visual field, information regarding the location of

that object is available to both hemispheres. This is potentially one reason why asymmetries

for the processing of visuospatial information tend to be less distinct than those for the

manipulation of linguistic material. There is obviously also a need for caution in extending

conclusions based on commissurotomized patients to "normals". The operations were

exclusively undertaken to relieve the symptoms of severe epilepsy it is almost impossible to

assess the damage sustained by the brain or indeed subsequent reorganization following

seizures. A sensitivity to individual neurological histories provides some measure of

accountability, however, one cannot realistically expect the severing of 200 million nerve

fibres to be without consequence. Certainly split brain research may be regarded as a single

element of a complex puzzle, though, the greatest contribution of these endeavors is likely

to have been the powerful impulse provided to the study of hemispheric asymmetries in

normal individuals.

2.3 ASYMMETRIES IN THE "NORMAL" BRAIN

In the period of almost four decades which has followed the instigation of split

brain studies, there has been a vast, one might conclude exponential, increase in the volume

of research which has aimed at elucidating the nature of hemispheric asymmetries in

normals. The flood of publications in recent years has approached a rate of almost four per

week (Allen, 1983). Obviously in face of this burgeoning accumulation of literature it is

possible to focus on barely a fragment of the field and to provide merely a flavour of the

research so delineated. Inevitably there will be omissions, however, the studies cited will

generally serve as illustrations of phenomena which have been widely and consistently

observed. Specific attention will again be given to the role of the right hemisphere in

mediating the manipulation of spatial relationships. 1 1

Page 26: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

The investigation of visual asymmetries in normal individuals has resembled very

closely that of cornmissurotomized patients. There has been a marked reliance upon brief

tachistoscopic presentations which permit the projection of visual information initially to

one hemisphere or the other. Of course in nonnal subjects, for whom the corpus callosum

is intact, information directed to one side of the brain is very rapidly made available to the

other. Nevertheless, lateralized presentation of stimuli does appear to result in lateralized

performance.

A number of researchers have obtained faster reaction times to brief stimulus

"flashes" presented in the left visual field (e.g., Anzola, Bertoloni, Buchtel & Rizzolatti,

1977; Berlucchi, Heron, Hyman, Rizzolatti & Umilta, 197 1; Jeeves, 1969; Jeeves &

Dixon, 1970), and these are differences which De Renzi (1978) attributes to tapping of a

right hemisphere superiority for elementary cognitive visuospatial operations. Similarly,

Kimura and Durnford (1974) comment on the attraction of the claim which posits that the

right hemisphere propensity for complex visuospatial functions is based upon asymmetries

of rather fundamental processes.

Certainly the asymmetrical processing of visuospatial information does appear to

exist at a number of levels. Left visual field superiority has been observed for the spatial

localization of dot stimuli (Kimura, 1969; Bryden, 1976; Pohl, Butters & Goodglass,

1972), whilst a reaction time benefit for the left visual field was obtained for the recognition

of "matched" or "unmatched" figures (Gibson, Filbey & Gazzaniga, 1970; Rizzolatti,

Umilta & Berlucchi, 1971). When symmetrical half figures are presented to different

hemispheres matching is accomplished more quickly if both figures are flashed to the right

rather than the left hemisphere @imond & Beaumont, 1972b; Egeth, 1971). Perception of

line orientation is accomplished with greater rapidity when stimuli are presented in the left

visual field (Kimura & Durnford, 1974; Atkinson & Egeth, 1973), as is evaluation of

curvature (Longden, Ellis & Iverson, 1976). The enumeration of dots (La Grone, 1942)

and other non-alphabetic stimuli (Kimura, 1966) is also apparently accomplished more

successfully by the right hemisphere. In addition, there exists some degree of right

hemisphere superiority for visual depth perception @urnford & Kimura, 197 1) and for

stereopsis (Cannon & Bechtoldt, 1969).

These asymmetries are sustained at what, for want of a more generally recognizable

conceptual framework, might be classified as higher order levels of processing. Whilst

there appears to exist a left visual field advantage for pattern displays (Moscovitch, 1979),

there is considerable debate as to whether the often cited right hemisphere superiority for

faces (Geffen, Bradshaw & Wallace, 1971; Rizzolatti, Umilta & Berlucchi, 1971) and face

like stimuli (Patterson & Bradshaw, 1975) is reflective of a facilitation in dealing with

Page 27: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

spatial or with emotional characteristics. However, it has been reliably demonstrated that

when employing rehearsal sets for which subjects are encouraged to employ either verbal

or imaginal mneumonics, a lateralized recognition probe will produce left visual field

benefit for the imagery condition (Seamon & Gazzaniga, 1973; Metzger & Antes, 1976;

Seamon, 1974), thus providing a least partial support for Bower's (1972) claim that the

right hemisphere would be dominant for information coded in terms of imagery. Similarly,

in the context of a study in which examination was made of effects due to memory set size,

Klatzky (1970) observed that responses to items presented to the left visual field became

more rapid for picture test stimuli.

Bogen (1969a) has suggested not only that on verbal tasks the left hemisphere

actually inhibits its partner, but also that the converse situation should occur when

visuospatial information is presented. Smith, Chu and Edmondston (1977) have reported

some supportive evidence employing a haptic discrimination task, and indeed, Hanis and

Can (1981) have suggested that a right hemisphere superiority for spatial manipulation may

potentially be elicited in a greater range of designs using tactual discrimination. The

consistently observed left hand superiority in the discrimination of braille letters (c.f.,

Harris, 1980) may arise as a consequence of this right hemisphere advantage (Hermelin &

O'Connor, 1971). Lateralized differences have been obtained for the localization of touch

upon the fingers (Nachson & Cannon, 1975; Bakker & van der Kleij, 1978). Data patterns

for tactual recognition also suggest a right hemisphere emphasis (Dodds, 1978). Clinical

evidence appears to indicate almost unilateral preeminence for the right hemisphere for the

manipulation of tactual information (Boll, 1974; Cannon & Benton, 1967, 1971). This

imbalance has been posited by Le Doux, Wilson and Gazzaniga (1977) to be that whcih

underlies the right hemisphere superiority for the mapping of all exteroceptive body space.

With the advent of sophisticated modern techniques it has been possible to utilize

"non-behavioural" indices of asymmetrical functioning in normals. Analyses of EEG

records during cognitive tasks have indicated that reduced levels of right hemisphere alpha

rhythm activity (alpha activity reflecting resting brain states) are associated with the solution

of block design problems (Galin & Omstein, 1972).

More recently, examination of evoked potentials (EP) has confirmed the greater

involvement of the right hemisphere in visuospatial tasks (Galin & Ellis, 1975;

Papanicolaou, Schmidt, Moore & Eisenberg, 1983). Associatively, Davis and Wada

(1977) concluded that there exists a differential hemisphere involvement in the cortical

processing of temporally and spatially ordered information. Techniques permitting the

study of regional blood flow in the two hemispheres have revealed greater right hemisphere

blood flow during a test of perceptual closure (Risberg, Halsey, Wills & Wilson, 1975). 1 3

Page 28: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Similarly, fledgling investigations employing positron emission tomography scans (PET) have confirmed anticipated asymmetrical changes in brain metabolism during verbal and

visuospatial tasks (Mazziotta & Phelps, 1983). Although the investigation of spatial ability has a hoary lineage, and there have been

a corresponding multitude of tests of "spatial sense" (Harris, 1978), there has been no

satisfactory definition of what spatial ability should comprisemd there has been a

corresponding failure to find an external correlate of spatial complexity per se. That which

constitutes an "operational definition", in the rare instances in which one has been

expressed, varies considerably between paradigms and even between studies ostensibly

manipulating the same parameter. There has been an associated problem in manipulating the

possible levels of spatial complexity. It is more often the case that a single task labelled

"visuospatial" is simply contrasted with one labelled "verbal". Efforts however, to move

from a descriptive to an analytic account of the potential mechanisms subserving, what are

clearly tangible asymmetries, have been altogether more problematic.

Page 29: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 3

THE NATURE OF HEMISPHERIC SPECIALIZATION.

3.1 LOCAL AND GLOBAL MODELS

There is now consideiable evidence to support the view that the cerebral

hemispheres are functionally asymmetric. In predictable moves, characteristic of those

disciplines which presume to provide some rational distillation of the workings of "the

mind", there have followed a multitude of attempts to provide some unifying theoretical

framework, some metatheory for the whole of laterality (Allen, 1983). These attempts have

taken the form of global models, initiated with the express intent of accounting for

hemispheric asymmetries in general, and those local models which, although initially

descriptive and typically confining attention to a particular experimental paradigm, have

become elevated to the level of explanation, most notably Cohen's (1972) seriUparalle1

distinction. Many have the status of having become "deeply rooted traditions" which can

seemingly fashion some accommodation of almost all apparently contrary evidence

(Sergent, 1983).

In addition to Cohen's (1973) separation of serial processing for the left

hemisphere, parallel for the right, it has been proposed that the left cerebral cortex is

specialized for, analytic as opposed to holistic, global, synthetic or gestaltic apprehension

(Nebes, 1978), verbal versus visuospatial activities (Kimura, 1961), focal rather than

diffuse processing (Semmes, 1968), name matching in contrast to physical matching

(Geffen, Bradshaw & Nettleton, 1972), and in terms of the traditional verbdnonverbal

distinction (c.f., Bradshaw & Nettleton, 1981). This list is by no means exhaustive. Allen

(1983) further classifies local models into basic mechanisms of; unilateral specialization,

bilateralization, hemispheric interaction (positive and negative), hemispheric parallelism and

allocation, though there could be similar application to global models. The first category is

self explanatory, whilst bilateralization entails that both hemispheres have equal capacity for

a given process. Positive interaction models provide for the hemispheres to interact

positively for a given function, whilst the reverse is true of negative interaction

formulations. Hemispheric parallelism suggests that the hemispheres operate

simultaneously and independently which contrasts with allocation, wherein normally only

one hemisphere processes information relevant to a given task at any one time.

Few now maintain, at least publicly, a strong version of unilateralization which

would correspond most closely to an acceptance of the strictest dichotomies inherent in the

local and global models, similarly, the form of bilateralization, which in its strongest 1 5

Page 30: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

expression is equivalent to equipotentiality, is apparently held by no-one. Allen (1983)

concedes that the other four mechanisms are embraced by bilateralization, further, they are

themselves not mutually exclusive. Although conceptually separable from unilateral

specialization, in view of present methodology, all mechanisms become practically

inseparable when the only, presently, tenable forms of unilateralization or bilateralization

are employed. In spite of Allen's (1983) claim that a general model can be formulated, his

postulation of distributed subprocessors performing functions analogous to the indefensible

"basic mechanisms" acts quite contrary to the principle of a unifying mechanism. It is clear

that basic mechanisms or subprocessors cannot characterize a local or global model per se,

rather the selection of a subprocessor or indeed basic mechanism is likely to depend on the

paradigm or manipulation it is one's wont to consider. Allen merely substitutes one

inappropriate level of analysis for another, however, in doing so he perhaps inadvertently

stumbles upon recognition of one of the fundamental limitations of laterality theorizing to

date, that "there has often been a rather strong implication-by-usage that tasks or functions

are unitary" (Allen, 1983 p.94). Although clearly prudent in emphasizing the need for "fine

grained analyses" of the subprocesses of what are, in reality, complex tasks and functions,

Allen is misguided in the belief that correlation of what appear to be stages of processing

with mythical subpmcessors, makes the latter any more worthy as a level of analysis than

that associated with the local and global models. Indeed the local and global themselves can

be shown to be of relatively little value on the basis of empirical evidence and upon a priori

grounds.

The most obvious limitation of the local and global models proposed thus far is that

they are represented as dichotomies. Whilst the proviso is conventionally attached, that a

strict dichotomy does not prevail (e.g., Bradshaw & Nettleton, 198 I), that the capacities of

each hemisphere lie at points on a continuum between two poles, and that differences are in

degree rather than of kind (e.g., Corballis, 1981; Milner, 1971; Zangwdl, 1960), the

boundaries are imposed by the limits of our conceptualization rather than by the nature of

the stratum they presume to describe. It is by no means evident that the brain "divides up its

functions into categories that correspond to our concepts or vocabulary" (Bullock, 1965).

Allen (1983) claims that there is some basis for reconciliation, that the various labels are merely reflections of a unitary underlying mechanism, however it seems that "cerebral

specialization is not likely to be less complex or more 'captured' by labelling one of its

attributes" (McKeever, 198 1 p. 74). Although it does seem reasonable that there exists a

common underlying mechanism, the conflict between schemes indicates that this has been

an inappropriate level of analysis.

Page 31: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Various reviewers, apparently oblivious of the limitations of dichotomies per se, in

what might be construed as a metanalysis of metatheories, have attempted to distill from the

global models some glorious unifying principle. As Cohen (1981 p. 67) comments "when

old dichotomies collapse under the weight of exceptions, psychologists seem to have an

irresistible urge to tidy up the field by reclassifying the data, and shoe homing it into a new

dichotomy". Clearly, it is these exceptions which are likely to prove more informative,

there would appear to be a good deal more worth in descriptive local models than some

contrived and inevitably inadequate grand theory. The point is not lost on McKeever (198 1

p.74), "the drive to neatly subsume all the essential aspects of hemispheric functioning

under some perfect dichotomy is an exercise in futility".

3.2 THE ANALYTIC - HOLISTIC DICHOTOMY

The approach favoured by Bradshaw and Nettleton (1981) is perhaps the epitome

of this "reclassifying urge". Selecting as a "straw-man" the verbaVnonverba1 dichotomy, in

a form so narrow that its acceptance by anyone would be in considerable doubt, these

authors run through a series of potential alternatives before settling on an analyticlholistic

dichotomy. Distinctions such as focddiffuse and seriaVparallel are apparently to be special

cases of the analyticholistic dichotomy, which in itself may be reduced to a left hemisphere

characterized by temporal order, and a right hemisphere by some form of spatial ordering

(Bradshaw & Nettleton, 1981). These alternatives however fare little better than the original

verbaVnonverba1 distinction.

Cohen's (1973) seriaVparalle1 dichotomy, which has been favoured by a number of

theorists of motor control (e.g., Todor & Dome, 1978; Nachson & Cannon, 1973), has

become established in the literature in a form which bears only a tenuous link to Cohen's

original formulation. In its received guise, it is held that the left hemisphere processes all

information in a serial fashion, whilst the right operates upon stimuli in a parallel manner.

Cohen (1973) was more circumspect, limiting the claim to alphanumeric stimuli, however

this "weak" version is in itself difficult to sustain, discrimination between serial and parallel

systems requires more complete and precise information than is conventionally obtained

from "psychological experimentation" (Townsend, 1972). Indeed even within the context

of the living body considered as an information processing system, attempts to draw

distinctions between serial and parallel processing in this manner must be seen as quite

misguided. This approach to cognition has recently received considerable criticism, Allport

(1980) highlights that a model encapsulating multiple entry of information at multiple points

is more appropriate than a serial foxmulation of successive bit entries at a single point. By

Page 32: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

this perspective there are essentially few limitations on the amount of information which

can be received.

The extent to which even language production and comprehension may be

considered as serial processes has recently been reassessed (Poeck & Huber, 1977).

Certain aspects of speech and memory for verbal items cannot be accounted for by a

sequential mode of operation in the left hemisphere and the right hemisphere can itself

engage in sequential processing (Moscovitch, 1979). Tactual patterns and melodies appear

to be apprehended as some unitary form and demonstrate a right hemisphere superiority,

although initially they may be scanned sequentially (Cannon, 1981; Witelson, 1974). As

Bradshaw and Nettleton (198 1) themselves admit "parallel processing may still be a

consequence of an analysis of a configuration into its component elements, each element

still being processed concurrently with its partners, however, though not in a holistic global

manner" (p. 58). The basis for distinction has thus been removed, assignation of serial or

parallel characteristics to a given process can seemingly be made post hoc in an arbitrary

fashion.

It seems the analytic/holistic resolution must itself suffer the same fate.

Insurmountable problems both theoretical and practical appear to preclude any useful

application of the distinction. Not least of the objections is that "there is no theory about

what 'holistic' or 'global' processing might be" (Churchland, 1986 p. 199). Operational

definitions have been no more successful, the consequence is a constantly shifting sense of

what holism or analysis may be, not altogether unwelcome to theorists who are incapable

or unwilling to relate what may constitute a practical test of a favoured dichotomy. The arcs

and circles test favoured by Nebes (e.g., 1978) illustrates the point. Right hemisphere

superiority was observed in the matching, test leading Nebes to conclude that holistic

processing was involved, subjects were ostensibly displaying the ability to form a whole

circle gestalt from the component arcs. Had alleft hemisphere advantage been observed, it

is likely the explanation would have emphasized the analytic procedure of dividing circles

into constituent arcs (Marshall, 1981). It is evident that the analytic/holistic distinction is

not presently, and cannot be, sufficiently well defined to serve as the basis on which to

predict experimental outcomes.

3.3 SPATIAL VERSUS TEMPORAL?

One is left with that distinction to which all dichotomies purportedly reduce,

temporal processing in the left hemisphere, spatial processing in the right (Bradshaw &

Nettleton, 1981). This has at least found favour with some commentators (e.g., Corballis,

198 1; Nottebohm, 1979,198 1; Tallal, 198 1; Wyke, 198 I), though once again the 1 8

Page 33: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

distinction is beset with problems which quite dissolve its utility. Attempts to dissociate

space and time have existed more in the minds of philosophers than in the world with

which we deal, for instance, it is the very essence of movement that it comprises series

which are both spatial and temporal. The fundamental irrationality of a dissociation of the

spatial Trom the temporal has not been lost upon modern theorists. Marshall (1981) points

out that having postulated that there exist distinct mechanisms for the manipulation of

spatial and temporal information, one immediately needs to speclfy some unifying device

which would integrate this information within the overspreading tempomspatial continuum,

whilst Sergent (1983) considers that "temporal and spatial dimensions are such basic

properties of any experience that it is hardly conceivable that each hemisphere would be

bereft of one of them" (p. 482).

Even if one acquiesces that it is not space and time as such which are handled

differently by each hemisphere, but rather perception or execution of the spatial or temporal

aspects of tasks, it is not clear that the increasing ambiguity is accompanied by any

pragmatic advance. The problem exists that it is impossible to dissociate the bulk of

"perception" in this manner. Perception would appear to have as its goal the resolution of a

stable, spatially ordered world from, for example, a temporally ordered series of glances

(Morgan, 1981).

Quite apart Trom the theoretical objections one must raise toward a spatiaVtempora1

dichotomy, the data is in itself sufficient to dispel apirations for this illusory distinction.

Music has been considered the epitome of temporality (e.g., Jankelevitch, 1977), yet the

right hemisphere superiority for the processing of such has been extensively catalogued

(e.g., Critchey & Henson, 1977). Singing also appears to proceed normally in patients

with left hemisphere lesions suffering fiom Broca's aphasia (Yamadori, Osumi, Masuhara

& Okubo, 1977), yet few would dispute that singing requires the mediation of duration,

sequencing and temporal order (Marshall, 1981). Additional material specific laterality has

been demonstrated in brain damaged individuals, verbal and nonverbal sequencing abilities

were differentially affected by the side which sustained damage (Kim, Royer, Bonstelle, &

Boller, 1980). The same double dissociation appears to be present in visuospatial and

verbal sequencing tasks (e.g., De Renzi & Nichelli, 1975; De Renzi, Faglioni & Previdi,

1977). There is clearly a spatial component to writing, yet this is a skill which, it is

assumed, is mediated by the left hemisphere (Hecaen & Albert, 1978; Peters, note 1).

Visually presented words and letters are comprised of spatial features, as are tactual

presentations, nevertheless there is overwhelming evidence demonstrating that recognition

of alphabetic material is accomplished primarily by the left hemisphere. Indeed stimuli

which are physically identical may be processed differentially by each hemisphere in a 1 9

Page 34: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

context specific fashion . Significantly, examples of spatiotempd interactions have also

been observed (c.f., Barlow, 1979; Morgan, 1980).

The spatial/temporal distinction is thus as deficient as any other previously

proposed. It should come as little surprise that this is the case, rather what is more puzzling

is why we should anticipate that hemispheric asymmetries are reducible to a single

principle. There is some case to be made for retention of the distinction as some heuristic,

to be used with clearly defined terms of reference, though Churchland (1986) is less

magnanimous, "the hypothesis is really a metaphor in search of a reality to give it

substance, and it may be more misleading than helpful" (p. 200).

3.4 A RESTRAINED RESOLUTION

One must necessarily conclude that the present confused portrayal of hemispheric

asymmetry is a consequence not only of the impoverishment of experimental and

conceptual approaches but is additionally a reflection of the multitude of factors which are

at work (Bertelson, 1981). Sergent (1983) has proposed that some resolution of this

problem may be achieved through the rigid control of incoming information. In addition

having acknowledged the multifactorial nature of many tasks it is equally important that

attempts are made to sample the effects of task upon task subcomponents through the

concurrent use of multiple measures rather than, as has been conventional, a single criterion

of task performance. With the appropriate fine grained analysis (c.f., Allen, 1983), it may

be possible to tease out the effects of a number of factors upon expressions of asymmetry

at a number of levels within a given task.

As Hammond (1982) suggests, if specialization of the two hemispheres does exist,

it is not for psychological but for physiological functions. The brain must deal with "neural

information" not with abstract categories. What exists at present is a problem whereby

Western philosophical traditions have sanctified what, with respect to hemispheric

asymmetries, has been a less arduous approach, pseudoanalytic explanations in terms of

convenient symbols or labels. The matter is succinctly stated by Rorty (1979, p. 237),

"That is to say that if physiology were simpler and more obvious than it is, nobody would

have felt the need for psychology".

Sergent (1983) makes an attempt to bypass the pseudoanalytic level of the local and

global model through an examination of the relationship between hemispheric asymmetries

and neural correlates extracted from the sensory areas. Certainly there is a pressing

requirement that neuropsychological findings be integrated with "cognitive psychology".

As outlined, a detailed analysis of an individual's responses with respect to the

Page 35: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

characteristics of both the sensory input and task objectives may prove to be particularly

revealing.

This should not be regarded as a return to some form of associationist approach

which denigrates the role of cognition. Rather, it is an acknowledgement that there is little

to be gained, in terms of elucidating the processes underlying motor control, by equating

higher levels of processing with the symbolism which is the cornerstone of cognitive

psychology. As far as its role in the explanation of asymmetries is concerned, whether

manual or otherwise, it has been demonstrated that the construction of local and global

models operating at the symbolic level, far from providing illumination, has proved to be

almost entirely regressive. There are reasons to believe that this level of analysis is totally

inappropriate.

Searle (1984) finds no use for the level of symbolic representation which forms a

central role in cognitive science. This is a middle level between the physiological and the

phenomenological which reflects tenets of a mentalistic approach derived from the Kantian

model. Searle (1984) contends that two levels of explanation are sufficient and indeed

justified, the level of intentionality in the form of a "plain English" description of

behaviour, and a neurophysiological explanation of this behaviour. Offering objections of a

similarly fundamental nature, Dreyfus (1979) argues forcibly that it is non-sensical to

consider a third level of explanation between the physical and the phenomenological as a

coherent level of discourse.

The apparent rewards to be obtained by locating a psychological level between the

neurophysiological and the purely phenomenological have apparently sanctified the

adoption of an explanatory level for which the relationship between the other two is

certainly ambiguous.

Local and global models and the dichotomies they encompass may potentially be

considered as aids to description but not as means or levels of analyses. There is thus some

legitimacy in suggesting that a task which appears to emphasise the sequential processing

of material at a given level of description is accompanied by a left hemisphere superiority

on a certain response measure, or that a task involving the manipulation of complex spatial

relationships is performed more effectively, with respect to a given criterion, by the left

hand. It is quite another matter to subsequently conclude that the left hemisphere is

specialized for the sequential processing of information and that the right is superior for the

processing of spatial relationships.

It is also important that some consideration be given to the selection of response

measures. As an illustrative example, it may be useful to consider performance on a

repetitive finger tapping task It is usually found that the right hand performs in a superior 2 1

Page 36: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

fashion, relative to the left, with respect to the criterion used to assess performance,

specifically the frequency of tapping. It has generally been concluded that this reflects a left

hemisphere superiority for the sequential control required to make rapid postural transitions

(c. f., Peters, 1980). Suppose however that it is determined that the criterion employed to

assess quality of performance will be the accuracy with which the spatial relationships

inherent in the task are perceived. Consider, in addition, that there is established a means of

measuring the accuracy of the perception independently of the measure of tapping

frequency, if a right hemisphere superiority is now found on this measure, can it be

concluded that the right hemisphere is superior on a tapping task? At present it is simply the

case that the response measures frequently employed are of an insensitivity such that the

conclusions drawn merely indicate assumptions of global superiority for various tasks.

Until there is examination of the processing subcomponents and asymmetries

therein, there can be no approach upon an adequate description of task asymmetries in

general and manual asymmetries in particular. Laterality effects obviously exist at a

multitude of stages within any task structure, any account of motor control processes will

be incomplete without consideration of these asymmetries and the factors to which they are

sensitiveh similar fashion, one goal at this juncture should be the detailed delineation of

the factors which are likely to influence asymmetry of performance at a number of stages,

and in this manner aim to establish some convergence with the realm of physiology.

Page 37: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 4

HANDEDNESS AND CEREBRAL SPECIALIZATION

4.1 PREFERENCE AND PROFICIENCY

It hardly seems worthy of comment, that most individuals are willing to express a

clear preference between the hands with reference to the performance of simple, or indeed

quite sophisticated, motor tasks. Yet, what appears self evident has in fact been critically

examined by a number of authors, notably, Barnsley and Rabinovitch, 1970; Benton,

Meyers and Polder, (1962); Palmar, (1964); Todor and Doane, (1978) and Heuer, (1987),

who concur in concluding that the relationship of hand preference to observed proficiency

is, at best, "moderate". Indeed, as Annett (1970a) outlines, although preference is generally

consistent with the writing hand, there can exist considerable diversity on simple tasks

requiring manipulation of the fingers, such as threading a needle or dealing cards.

Whilst Doane and Todor (1978) consider as problematic the observation by Satz,

Achenbach and Fennel1 (1967) that manual proficiency appears less consistent when

individuals are classified on the basis of hand preference rather than proficiency, this

heterogeniety is not unanticipated. There is certainly little justification for considering the

distribution of proficiency to be any more unidimensional than that for preference.

Although it is certainly the case that the widespread use of handedness questionnaires has

led to considerable misclassification in terms of proficiency, it is not clear that the use of

proficiency measures to establish proficiency is an entirely satisfactory alternative. Rather,

a problem arises when any simplistic measures of either preference or proficiency are taken

as indices of underlying functional or structural organization.

The problems related to this approach have probably been most clearly

demonstrated with regard to "left handed" individuals. Heuer (1987) has criticized the

concept of "handedness" as it fails to distinguish between hand preference and hand

superiority. It appears possible to subdivide the population of left handed individuals into;

unilateral left handers, "ambidextrals" and "ambisinistrals" (Todor & Doane, 1978) on the

basis of a number of performance measures. Unilateral left handers are taken to display the

characteristic "strong" dominance associated with right handers, ambidextrals displaying

enhanced performance on both hands, whilst ambisinistrals perform poorly with both

hands. This has generally been taken to indicate the partial or incomplete lateralization of

function which has also been observed, for left handed populations, on a number of

measures of higher cognitive processing (Levy, 1969; Bryden, 1965) and on the basis of

clinical evidence (Luria, 1970). There has arisen, as a result, a perspective which views left 2 3

Page 38: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

handers, not as some unitary group but rather, as individuals located upon a continuum of

lateralization. It is clear however that there has been less enthusiasm in applying this

construct to right handers, for whom output functions are subserved by, what appears,

essentially the same neurological substrate yet for whom the effects of incomplete

lateralization are taken as less clear, and for whom the consequences are interpreted as, or

masked by, reflections of variations in manual proficiency rather than as varying patterns of

cerebral organization. As Flowers (1975) points out, the tasks generally employed as

proficiency measures involve widely differing aspects of controlled movement, it is

certainly not the case that asymmetries will be expressed equivalently in all instances.

Annett (1985) concludes that an individual's choice of hand relies on more than

relative proficiencies, depending also on a decision criterion which is subject to influence

by, among other things, external social pressure, though it is to be expected that few

contemporary subjects were exposed in their "formative years" to measures such as the

strapping of the "sinistral" hand behind the back. Annett's (1985) formulation is derived

from a unitary concept of skill (Heuer, 1987), a position which is certainly untenable. As a

variety of tasks is considered, correspondences based upon the combination of decision

criteria and relative proficiency themselves become equivocal. There are certainly tasks on

which the nonpreferred hand may be "superior" to the preferred one (c.f., Todor & Smiley,

1985).

Proficiency is an observable, a "reflection on the surface of motor systems" to

paraphrase Marin (1976), which is in turn not directly related to any one other variable such

as task complexity (Steingruber, 1975; Todor & Doane, 1978) but is subject to the

influence of factors operating at a number of levels. Thus, in any attempt to relate hand

proficiency to asymmetries of structure or function one must be sensitive to the presence of

a range of possible mediating factors. As has been stressed previously, laterality effects

expressed in terms of output measures are indicative, not merely of some structural

asymmetry, but also, of the imposition of task specific constraints and functionally higher

levels of motor control, upon both the neural substrate and upon output mechanisms. It

would thus appear that there exists a need, not only to establish the relationship existing

between measures of hand preference and those of hand proficiency but, rather more

importantly, to establish the mechanisms and structures which subserve each.

It appears to be common practice, in the literature, to directly attribute hand

proficiency or superiority on various tasks to the specialization of the contralateral cerebral

hemisphere (Heuer, 1987). Certainly, hemispheric specialization is likely to be a major

determinant of manual asymmetries, however, there are a number of considerations which

ought not to be overlooked. In the first instance, and as has been highlighted in the 2 4

Page 39: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

previous section, the assumption of unitary task structures is unwarranted. The use of a

small number of dependent measures assigned by an experimenter can merely touch upon

the subtleties within the task gestalt and certainly may often exclude what the subject

perceives to be his "action goals". Secondly, it is necessary to consider the imposition of

functionally higher levels of motor control which themselves may or may not be

represented asymmetrically (Heuer, 1987). The following section will deal with a third

potential reason for caution, the relationship of the output of the two cerebral hemispheres

to the motorneuron pools located in the spinal cord. The situation is summarized by Heuer

(1987, p278) "the relationship between hand superiority and hemispheric specialization

poses a problem of enquiry". As there is no simple way to infer hemispheric specialization

from the performance of the contralateral hand, the reverse also holds true

4.2 THE CONTRIBUTION OF DESCENDING PATHWAYS

There is considerable anatomical evidence to suggest that there exist

"corticomotoneurona1" connections directly to the distal musculature of the hands,

pathways which are implicated in the independent movement of, in particular, the fingers

(Brinkman & Kuypers, 1973; Kuypers, 1978; Lawrence & Kuypers, 1968a; Lawrence &

Hopkins, 1976). These are pathways which may be distinguished from other parts of the

Cortico Spinal Tract, in having only monosynaptic connections, though it should be noted

that those pathways comprised of disynaptic and trisynaptic connections will not "cross" when otherwise "uncrossed", as a consequence of synapsing within the spinal cord. With

reference to the control of more proximal muscles, less direct "uncrossed" pathways may

also be involved (Gazzaniga, Bogen & Sperry, 1967; Zaidel & Sperry, 1977). Theorists

have, as a result, postulated that hand differences, arising from contralateral cerebral

specialization, may not exist for movements predominantly involving the proximal

musculature (Todor, Kyprie & Price, 1982), whilst many other studies of hand differences

rely upon the assumption that control of the hands is accomplished by the contralateral

cerebral hemisphere (Todor & Smiley, 1985). There have been recent demonstrations

(e.g., Kuypers, 1984) that considerable control may be exerted even without recourse to

corticomotoneuronal pathways, it will prove useful to consider the routes by which this

may occur.

Of the four descending pathways have been outlined by Kuypers (1981), the most

functionally substantial of which is the corticospinal tract. The majority of these fibres

cross to the contralateral side within the medulla, though a small number are thought to

cross below the brain stem, crossing at segmental levels via interneurons. Whilst

corticospinal fibres are responsible for the innervation of distal musculature, it also appears

Page 40: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

that proximal muscles may be similarly controlled (Kuypers, 198 1). The notion of simple

and direct contralateral control is further eroded when one considers that the majority of

these pathways, with the possible exception of those innervating some finger musculature,

comprise many interneurons and collaterals, even for many finger movements, one cannot

assume that all pathways are crossed. It is, however, the functioning of the direct pathways

which apparently cannot be undertaken by other fibre tracts, lesions of the corticospinal

tract in neonates prevents the development of differentiated finger movements (Todor &

Smiley, 1985). Corticospinal innervation is also extended to proximal musculature, the

effects of which become most evident when task requirements emphasise the need for

contralateral control (Di Stefano, Morelli, Marzi & Berlucchi (1980); Todor, Kyprie &

Price, 1982).

The rubrospinal tract, originating in the red nucleus, which is itself located in a

region of the midbrain, provides a second crossed pathway which appears to be associated

with the control of hand movements. The maintainence of capacity for control of the hands

which survives following disruption of the corticospinal tract, is curtailed when the

rubrospinal tract is sectioned (Todor & Smiley, 1985). However, with regard to the

rubrospinal tract, it is at present unclear as to the nature of the connections above the level

at which this pathway appears to originate. The nature of the connections are such that a

pathway that appears crossed may in reality be uncrossed

A third potential means of control, for the proximal and axial muscles at least, is

provided by the reticulospinal and vestibulospinal pathways. These proceed ipsilaterally

within the spinal column, however the bilateral projections from this tract appear to

contribute little to the fine control of the hands (Todor & Smiley, 1985).

In addition, there appear to exist direct brainstem pathways which alter the

exciteability of the motoneuron pools. Kuypers (198 1, 1984) has identified these tracts as

some of those descending from the raphe nucleus. Whilst these pathways directly synapse

with the motoneurons associated with the distal musculature, they also possess collaterals

which project multisegmentally (Todor & Smiley, 1985).

One must acknowledge then that many movements may be primarily but not

exclusively under contralateral control. Although the corticospinal tract is largely comprised

of crossed fibres, it is an open question as to how the excitation of the motoneuron pools

innervated by this and other descending pathways is affected by functionally higher levels

of control. One need only note the effectiveness of the Jendrassik procedure in which the

exhibition of spinal reflexes is enhanced when an individual attempts to pull apart his

tightly clasped hands. It seems quite plausible that excitation of this kind may proceed

asymmetrically. Trevarthen (1984) has speculated, on the basis of research conducted by 2 6

Page 41: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Grillner and Zangger (1979) demonstrating that the spinal locomotor system may consist of

distinct left and right "generators", that a slower system in the left side of the human spinal

cord may account for some portion of exhibited hand differences. Certainly, one ought not

to dismiss the possibility that asymmetries exist below the cortical level.

4.3 DEFICIENCIES IN THk "STRUCTURAL" APPROACH

The impoverishment of any approach which posits that between hand differences in

"proficiency" are primarily due to a structured contralateral connection with a specialized

cerebral hemisphere has been illustrated by series of studies demonstrating that advantages

in terms of choice time are due to the effects of spatial compatibility rather than elementary

anatomical connectivity.

On the basis of "classical" research (e.g., Proffenberger, 1912), it had for some

time been considered that simple reaction times to "unstructured" lateralized stimuli were

determined largely by structural constraints, and therefore, that ipsilateral responses, for

example stimuli to the left hemiretinae requiring responses with the left hand, would be

concluded more rapidly than contralateral responses. This, in turn, relies upon the

assumption that ipsilateral responses can be mediated by intrahemispheric hemispheric

processes. Indeed, the latency difference between ipsilateral and contralateral responses has

been viewed as an estimate of interhemispheric transmission time (see Bashore, 198 1 for a

review).

Contemporary research has consistently demonstrated that the time taken to respond

in a choice situation can be potently affected by altering the relationship between the

location of the stimulus and the spatial position of the hand making the response (e.g.,

Simon, Hinrichs, & Craft, 1970; Wallace, 1971; Brebner, Shephard, & Cairney, 1972).

Compatibility effects do however appear to depend on other task constraints, Anzola,

Bertoloni, Buchtel & Rizzolatti (1977) confirmed the superiority of the ipsilateral response

for simple reaction time, yet demonstrated that when subjects were required to decide

which hand to employ depending on the spatial position of the stimulus, the faster response

was now accomplished by the hand which was in the same visual space as the stimulus,

regardless of whether the anatomical connections were contralateral or ipsilateral. The

required experimental manipulation was achieved by having the hands of the responding

individual "crossed" or "uncrossed" in front of the body. Anzola et al note that the extent to

which the effects of spatial compatibility may be expressed will be dependent upon the

"information content" of the stimulus, concluding that "when the task does not require the

necessity of making a decision, the directness of the anatomical connectivity between the

receiving hemiretinae and the responding hand prevails" (Anzola et al, 1977, p301). There

Page 42: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

are clearly few instances in which an individual will proceed with a "motor act" in the

absence of "decision making" of any kind.

These findings have been extended by, among others, Cotton, Tzeng and Hardyck

(1980) and by Ladavas (1987) who demonstrated that spatial compatibility effects occur in

the absence of any overt correspondence between the spatial attributes of a stimulus and the

required response. Both investigations revealed not only that right hand responses are made

more rapidly to right hemifield presentations and vice versa, but also that the right hand

responds faster to "right up" and "left down" positions, and the left hand responds faster to

"left up" and "right down" positions, when stimulus lights appeared not only to the right or

left of, but also above and below fixation.

The diminishing importance of elementary anatomical connectivity between central

and peripheral regions as task constraints are imposed is paralleled by indications that

anatomical factors at the cortical level become less significant as "demands" are increased

Bashore (1981) has reviewed evidence which suggests that estimates of interhemispheric

transmission times 0 derived from sim~le reaction time tasks are well correlated with

electrophysiological measures. These measures involve the subtraction method

(Poffenberger, 1912) and assume that "transmission of simple sensory information and the

initiation of uncomplicated movements are mediated over fixed and reasonably well isolated

neuroanatomical pathways" (Bashore, 1981, p. 353). It appears however, that as task

complexity increases along a number of dimensions and moves away from simple reaction

time, estimates of M?T are considerably elevated Presumably, the "fixed"

neuroanatomical pathways are unchanged, yet the alterations in the cerebral activation

responsible for these increases remain unclear. They do appear to arise as a consequence of

the type of movement required for as a response (e.g., Krsiteva, Keller, Deecke &

Kornhuber, 1979). Investigations conducted by Di Stefano and co-workers @i Stefano et

al, 1980) produced indications of response hand advantages for abductive lever pulls but

not for key press responses in what was otherwise a simple reaction time study. Estimates

of M?T are also considerably altered by, the required complexity of decision making,

where the more complex decisions are presumably engaging more extensive "cognitive"

processes, and by structural characteristics of the stimulus itself (c.f., Sergent, 1983). In

concluding his review, Bashore (1981, p. 366) states, "intuitively, one is led to

hypothesize that intrahemispheric processing and interhemispheric communication are

integral functions of stimulus input, information processing requirements, and motor

output". As will become apparent, that which appears to critically modify IE-I'IT can be seen

to strongly influence manifestations of hemispheric asymmetry in general. In the sections

which follow, the relationships between these factors will be more closely examined. 2 8

Page 43: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 5

AN "INDIRECT APPROACH

5.1 THE SIGNIFICANCE OF THE STIMULUS INPUT By way of introduction to her synopsis of visual asymmetries, Sergent (1983)

outlines her grievance that, of the factors which might potentially influence the expression

of laterality, implicitly Bashore's three factors, the characteristics of the input have been

afforded only the most superficial consideration,

neuropsychologists emphasized the processing characteristics of the tasks required from subjects, and did not consider the characteristics of the stimulus as a major causative agent, but only as the instigator of behavior (Sergent, 1983, p. 482).

The author highlights the dependence of the developing brain upon sensory stimulation and

considers that, in terms of elucidating the relative competencies of the cerebral

hemispheres, one must, as a logical first step, examine the manner in which the quality of

the input varies as a function of the attributes of the entire visual system (Sergent, 1983).

This might be seen as constituting a description or explanation at the physical level and

should perhaps be viewed as complimentary to the approach of direct perception (Gibson,

1966) or direct action (e.g., Turvey & Carello, 1986). It is Sergent's view that only

through systematic control of the incoming information may asymmetries be assessed. For

incoming information one should perhaps read stimulus energy as it is this which Sergent

(1983) considers to be the determinant of the characteristics of incoming information. One

can see how this may be directly related to some quite fundamental tenets of the "ecological

approach", in particular, that the lawfully based flow fields of light, sound and touch

associated with an object give rise to a unified impression of that object, even though these

flow fields are considered to be different stimuli and of different energies (Turvey &

Carello, 1986). These flow fields are, however, characteristic of that object at that instant.

A different object will have associated with it different flow fields and, in each modality,

different "stimulus energies" thus giving rise to a different impression. Although there is

clearly a perceptual constancy in that, whilst the stimulus energies associated with an object

may change over time for example as a result of movement, the identity of that object is \

viewed as invariant. This does not preclude, of course, that more generally what are at any

instant different stimulus energies are associated with many objects and therefore give rise

to impressions of many objects. It seems to follow that ones impression, ones "perception"

is critically determined by the stimulus energy of that which is being perceived. Husserl

Page 44: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

would have held that the constitution of space and objects begins with the "visual field", the

"visual sensations available when the eyes, head and body are at rest" (Scheerer, 1986, p.

164). The visual field identified by Husserl is essentially that envisaged by the Gestalt

psychologists or the "Gibsonians" (Scheerer, 1986), thus, if one proceeds with this line of

reasoning, it follows that the stimulus energies reaching even the static eye will have

consequences in terms of the received impression of space. Similarly, variations in

stimulus energies, other than those associated for example with a single object over time,

will lead to variations in the received impression of space. More importantly in this context,

asymmetrical reception, conversion and transmission of this energy by the nervous system

will result in an impression of space which, when assessed through the use of behavioural

measures, will itself appear asymmetrical. This follows in a manner which does not

compromise the necessity of employing two levels of discourse, physical and

phenomenological, as outlined by Dreyfus (1979) and Searle (1984). As such, the work of

Sergent (1983) may assume a broader significance, though perhaps not in the manner that

author had intended.

Clearly, there are practical, not to mention philosophical, difficulties in dissociating,

what in the language of cognitive science would be, cognitive and sensory operations,

however some attempts have been made to consider independently the asymmetries which

may arise at these pseudo stages. Sergent (1983) is probably misguided in her selection of

the point of demarcation of sensory from cognitive, nonetheless as an aid to exposition, it

will prove useful to adopt her heuristic that the "sensory processing" of the relevant stimuli

has been "neurophysiologically localized" in the visual sensory areas of the left and right

occipital cortex. Considering asymmetries in stereopsis, the perception of colours, and the

duration of iconic storage, Sergent (1983) dismisses elicitations of what are apparently

laterality effects, by concluding that these investigations may be sampling "elementary

cognitive visuospatial operations". Whilst questioning the possible ecological utility of an

asymmetrical sensitivity to the visual world, Sergent (1983) does acknowledge that further

research is required.

What is more puzzling is that which Sergent (1983) ascribes to be "hemispheric

processing beyond the sensory level" (p 492), or cognitive processing. The problems of

this approach are quite evident when one considers that included in the subcategory of

'state limiting variables' are those which are affected by variations in exposure duration,

luminance, stimulus size and retinal eccentricity or the introduction of visual masking.

Whilst the means of analysis may be dismissed, more interesting are the observations that

the direction and magnitude of observed asymmetries may be directly influenced by

duration and luminance and thus by stimulus energy (e.g., Sergent, 1982, c,d, & f). The 3 0

Page 45: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

most important conclusion one may draw is that articulated by Sergent (1983, p 493, that

"the two hemispheres are not equally affected by variations in stimulus energy", though by

noting that it is the resulting 'visual information' upon which cognitive operations are

performed, the original sensorylcognitive distinction seems to have been quite dissolved.

Evidence has also been presented which appears to suggest that the effects of retinal

eccentricity and stimulus size are similarly asymmetrical (e.g., Polich, 1978; Sergent, 1982

b;c). It is not necessary to consider in detail what Sergent (1983) terms "process limiting

variables", suffice to say, the influence of what are apparently mediating cognitive

"operations" are treated elsewhere. There can however can be no objection to Sergent's

closing comments that "one cannot make unequivocal predictions about the outcome by

considering only the quality and characteristics of the input" (1983, p 506), a point which

has indeed been stressed throughout this review. Having given some consideration to

stimulus input, the following section will deal with the influence of what Bashore (1981)

would view as the "information processing requirements of a task

5.2 THE DUAL TASK PARADIGM

The practical manipulation of the information processing requirements has generally

involved tasks in which "cognitive operations" of various kinds are performed concurrently

with some kind of manual activity. Designed initially as a means with which to investigate

functional lateralization in a broader sense, the paradigm has been extensively employed to

examine the relationship between cerebral specialization and the proficiency of the preferred

and non-preferred hands. I Associated with the use of the Dual Task Paradigm are a number of assumptions,

both explicit and implicit (Todor & Smiley, 1985). Following Kinsbourne and Cook

(1970), interference or facilitation (though more usually the former) will occur if the two

tasks ("cognitive" and "motor") which are usually associated with the differential activity of

one hemisphere, are performed simultaneously. The rationale was extrapolated by

Kinsbourne and Hicks (1978) who assumed that the extent of this effect was determined by

the "functional overlap" within a given "controlling" hemisphere. It has also been

maintained that, for a given "dependent" task, (conventionally the manual task) the

interference resultant upon the concurrent (usually cognitive) activity may be unilateral,

bilateral of asymmetrically bilateral depending on the specific processing requirements of

that activity (Allen, 1983; Friedman & Polsen, 198 1; Hellige & Longstreth, 198 1). Clearly

the motor task is not bereft of cognitive components, and similarly, all cognitive operations

require for their expression some form of motor output and thus control, whether this is a

pointing response or overt vocalization. Indeed Lomas (1980) in work (to be discussed 3 1

Page 46: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

shortly) which was controversial but insightful, drew attention to the need for consideration

of the intrahemispheric interference which may occur, and in particular the specificity of

this interference with regard to the level, within some stimulus to response continuum, at

which this interference may occur. In a similar vein, Todor and Smiley (1985) highlight

that not only is the assumption of exclusively contralateral control via crossed anatomical

pathways not supported, but also that movement related activity in the brain stem and

higher centres may proceed asymmetrically. Their qualifications are worth quoting at

length,

it should be noted that preceding a unirnanual movement using crossed corticospinal pathways, movement planning may have occmed bilaterally. This movement planning would have involved cortical areas such as the supplemental motor areas, frontal association areas, premotor area and subcomcal structures such as the basal ganglia and the cerebellum. Although the motor outflow may be more or less restricted to the motor area of a given hemisphere, it may reflect the converging influence of other intra and inter-hemispheric structures (p. 320-321).

In view of the multitude of factors to which the expression of laterality is likely to

be sensitive, it is perhaps of little surprise that use of the dual task paradigm has produced

"a rather complex pattern of results" (Bryden, 1982). In what might be regarded as the

prototypical experiment in what is now an extended collection of studies, Kinsbourne and

Cook (1971) required that subjects attempted to balance a dowel rod on the index finger of

their right or left hand. A control condition indicated that this task was performed in

superior fashion by the right nand. When a single interfering task was introduced, that of

speaking a sentence, a decrease in dowel balancing proficiency was noted for only the right

hand. The conclusion was drawn that the drop in right hand performance occurred as a

result of competition for "resources" within the left hemisphere, between speaking and the

manual task.

Attempts to extend the findings of unilateral interference to a variety of manual tasks

have produced results which are a good deal less clear. Lomas and Kimura (1976), in the

first of a series of three experiments replicated, at least for male subjects, the finding of

Kinsbourne and Cook (1971) in that concurrent speech was again found to disrupt right

hand dowel balancing. Humming was also used, as a task which was ostensibly mediated

by the right hemisphere, concurrent performance, on this occasion resulted in a depression

of dowel balancing proficiency for both hands. Considering the dowel balancing task to be

an inappropriate means of assessing the "motor generator", Lomas and Kimura (1976)

essentially replicated their initial experiment, altering only the nature of the motor task by

substituting a finger sequencing task for dowel balancing. Once again speaking decreased

preferred hand performance in right handers, though humming apparently exerted no 3 2

Page 47: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

effects. The final experiment of the series used sequential telegraph key strikes in place of

the sequencing task. Concurrent speech now resulted in a bilateral decrement in the rate of

single finger tapping and a unilateral depression of right sided performance for sequential

whole arm tapping. The latter result seems to run counter to intuition, particularly in light of

the presumed presence of direct contralateral connections for only the most distal

musculature. Subsequent findings of bilateral interference have not been untypical,

concurrent cognitive activity which emphasizes verbal "abilities" has generally resulted in

depressed right hand performance (e.g., Bowers, Heilman, Satz & Altman, 1978; Hicks,

Provenzani & Rubstein, 1975; Thomton & Peters, 1982) whilst tasks apparently requiring

right hemisphere mediation have, on occasions, produced greater decrements for the left

hand (e.g., Benton, 1979; Hellige & Longstreth, 198 1). In other instances equivalent

decreases in proficiency have been observed for both hands (e.g., Summers & Sharp,

1979). This pattern of bilateral interference further challenges the view that movements are

subject to exclusively contralateral control (Todor & Smiley, 1985).

In an attempt to explain the manner in which the extent of right hand interference

accompanying speech is dictated by specific task demands, Kimura (1979) and Lomas and

Kimura (1976) have postulated that it is interference between seauential movements and the

production of speech which is responsible for the depression of right hand proficiency.

From this perspective, the unilateral interference observed in the second experiment of the

Lomas and Kimura (1976) study is seen as arising because the finger sequencing task did

indeed involve sequential movements whilst the tapping experiments of the final study did

not. This assumption is made explicit, "the term 'sequence of movement' implies that the

task does not consist merely in the repetition of the same discrete movement over and over,

as in single finger tapping" (Lomas & Kirnura, 1976, p. 31). The explanation seems

somewhat ad hoc, one would have difficulty envisaging any movement which is not in

some sense sequential. McFarland and Ashton (1978a), using six verbal and six non-verbal

tasks and a manual response which required successive pressing of two keys, observed a

pattern of results in many ways similar to those of Lomas and Kimura. Verbal tasks

resulted in unilateral right hand disruption, whilst in the non-verbal conditions, a bilateral

disruption ensued. By way of explanation for what have been less consistent effects,

namely that primarily visuospatial right hemisphere tasks result in unilateral left hand

deterioration, McFarland and Ashton (1978b) argue that

the neural structures of the right hemisphere, which mediate the visuospatial cognitive task, may overlap only those right-hemisphere structures which mediate the spatial components of left hand performance but not those structures which mediate the spatial components of right hand performance (P. 344).

3 3

Page 48: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

It is important to note that with regard to the McFarland and Ashton formulation and

that of Lomas and Kimura (1976) which, in analogous fashion suggests that degree of

overlap may dictate the level of left hemisphere disruption, the distinction is functional

rather than anatomical or physiological. This is in spite of the liberal use of the term

"structure". The use of an explanatory construct such as "functional unit" has its obvious

limitations, by relegating the need for a physiological correlate, it is difficult to establish a

priori which tasks will interfere (Bryden, 1982). By adopting this perspective, one appears

to be quite at liberty to conclude that, since two tasks have interfered, there must have been

some overlap of functional space.

Whilst continuing to adhere to the view that the extent of interference is dependent

upon the degree of functional similarity, Lomas (1980) has proposed that consideration of

more specific functional overlap must be entertained. In Lomas's view, there has been a

general inability to demonstrate unilateral right hand interference with concurrent tasks

other than those associated with motor production of speech, included in this category are

both non-visual and visually guided motor tasks. It is further presumed that there has been

no appropriate demonstration of left hand deterioration in accordance with right hemisphere

interference. In an attempt to provide support for these assertions, Lomas (1980) employed

conditions in which individuals either could or could not have recourse to visual guidance

of axm and finger tapping, and obtained indications that concurrent verbal tasks interfered

only with motor tasks which did not utilize visual control. More contentious has been the

suggestion that it is not sequencing per se which is under left hemisphere control, subjects

were in each condition required to enact a sequence, yet interference was only evidenced

when the movement was not visually directed (Lomas, 1980). Rather, it was suggested that

the left hemisphere has, within its functional domain, a set of processes specifically

concerned with the control of movement transitions in the virtual absence of visual

information, this is the system which is in turn assumed to be implicated in speech

production (Lomas, 1980). Although this attempt at specificity is in itself admirable, the

generalizations made with respect to non-supportive literature are clearly too broad. In

addition, there is recent evidence that non-vocalized verbal tasks do have a disrupting effect

upon right hand performance (Ikeda, 1987). Although there exist interpretive problems, as outlined above, there have been

frequent indications that verbal tasks may unilaterally interfere with concurrent motor

performance and, admittedly less pervasive, data suggesting that the left hand may be

similarly disrupted by activity of an appropriate nature. In remaining consistent with what

has been a recurring theme, it is only likely to be through the subtle manipulation of

procedural variables, in conjunction with the use of behavioural measures of appropriate 3 4

Page 49: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

resolution and sensitivity, that the mechanisms of interest will be elucidated The rate of

rapid finger tapping is one measure which has been extensively used as both an index of

neurological damage (e.g., Kimura, 1977) and as a central dependent measure in a large

number of experimental investigations. There are certainly a variety of measures which may

be utilized in addition to the global appraisal of tapping frequency. It has been pointed out

(Peters, 1980; Todor & K ~ P A ~ , 1980) that the finger tapping task involves, in addition to

sensitively timed "posture transitions", sequencing between and within "motor acts" (c.f.,

Lomas & Kimura, 1976).

The work of Brodie (1984) represents at least one attempt to provide a more fine

grained analysis of the tapping task substructure. The dependent measures used to assess

tapping performance were; Inter Tap Interval, which was the time between successive key

closures and thus a measure of the frequency of tapping, Dwell, the duration of key

closure, Slack, which is assessed as the period between successive key depressions (ITI - dwell time) and the Maximum Force exerted during key depression. Rather than being

required to tap as rapidly as possible, subjects were instructed to maintain one of a number

of set tapping frequencies. Individuals were initially trained to tap in time with an auditory

tone, in an attempt to equalize the performance of both hands prior to testing, a requirement

Bryden (1982) identifies as essential for effective use of the paradigm. In the test situation,

tapping was evaluated after the tone had been removed, concurrently with four tasks and in

a control condition in which tapping proceeded alone. The latter condition is only one of

two controls Bryden (1982) feels are necessary precursors to analysis, the other being an

evaluation of performance on the "interfering" task, p t h when performed alone and in the

dual task setting. This may provide some means of telling whether decrements arise purely

as a consequence of performing two tasks simultaneously (capacity interference) or due, as

is generally assumed, to structural interference. The absence of these controls in a large

proportion of the early dual task studies, along with the absence of a training or

"equalization" period, may have contributed considerably to the ambiguous nature of many

findings. The four concurrent tasks utilized by Brodie (1984) were; Read, reading of a short paragraph upon which subjects were later tested for retention, Geo, pre and post

tapping matching of geometric figures, m, a rapid five finger sequencing task and &, involving slow single finger flexion. Somewhat unexpectedly, neither of the "cognitive"

tasks, Geo or Read, had any appreciable effect upon tapping performance. That this may

have arisen as a consequence of training is not without significance with regard to the

interpretation of many early studies. Concurrent performance on both motor tasks resulted

in appreciable interference of left and right hand tapping, to which the dwell component

was apparently most sensitive. The pattern of asymmetrical interference was complex and 3 5

Page 50: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

somewhat inconsistent, however, the data may be summarized as follows: performance of

the Prax task, with its emphasis on sequencing, seemingly required the involvement of the

left hemisphere when performed with either hand, however the interference was greatest

when tapping was performed by the right hand, as left hemisphere involvement was again

directly required. Conversely, the Flex test, somewhat tentatively, assumed to involve a

greater "spatial" component &d thus greater right hemisphere involvement, produced

interference which was "reversed" relative to that created by the Prax test. There exists

however an interpretive problem, as both tasks involve both hemispheres to some extent.

In line with the initial assumptions of the Dual Task Paradigm, a greater required

involvement of both hemispheres results in a greater potentiation of interference. Therefore,

in any comparison between two tasks, though both manual, where one task is assumed to

be primarily right hemisphere mediated, the other primarily left hemisphere mediated, the

extent to which interference is bilaterally expressed then depends upon the relative

involvement of the non-primary hemisphere in each task. The extent of this involvement is

obviously difficult to determine in advance, leading to problems equivalent to those which

beset explanations in terms of "functional space". Again there is no a priori method of

determining the level of involvement of the "secondary" hemisphere on the interfering task.

If there is bilateral interference it may be the case that the "secondary" hemisphere is highly

involved, alternatively there may be no "structural" interference between the dependent and

interfering task, the bilateral decrement may result rather from demands made upon an

overall "finite processing capacity" (c.f., Kahneman, 1973). It is also likely to be the case

that the relative involvement of each hemisphere is dictated, in part, by the overall task

structure, for example the Flex task may be primarily mediated by right hemisphere control

when performed in isolation, but is subject to increased left hemisphere involvement in a

dual task context (Anzola, Pulirneno & Rizzolatti, 1980).

The relative involvement of the "primary" and "secondary" hemispheres is a

function not only of the task context and the task itself but also of the level of practice on

the dependent task. Increasing the level of practice prior to testing reduces the potential of

finding interference effects (Bahrick & Shelley , 1958; Rodney, 1980). Practice trials on a

finger sequencing task,a day prior to testing, have been shown to obliterate the effects of

supposedly interfering tasks in a replication of the Lomas and Kimura (1976) study

(Rodney, 1980). As Bryden (1982) points out, it is important that the left hand be afforded

the opportunity to reach the same level of performance as the right hand, as a result any

effects of right hemisphere interference will be more faithfully exhibited.

As has been mentioned, bilateral interference may arise as consequence of

hemispheric interaction on the interfering task itself or as a result of overall capacity 3 6

Page 51: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

interference created when two "difficult" tasks are performed simultaneously. Such is the

contention of Summers and Sharp (1979) who revealed disturbances on motor sequencing

which were equivalent for both verbal and spatial interfering tasks, despite indications that

these tasks involve opposite hemispheres. An adequate test of structural versus capacity

interference requires that there exist a means of manipulating the difficulty or capacity

demands of a task which is assumed to provide structural interference. There is often no

straightforward means of obtaining a metric for assessing task difficulty (Bryden, 1982).

One is again left without a means of specifying, in advance, relative capacity demands.

Rodney (1980) motivated it seems by pragmaticsm, employed two levels of difficulty for a

vocal (structural interference) task which were distinguished by the number of words his

subjects were required to repeat, one or six. The second structural interference task

required motor sequencing, the levels of difficulty in this instance were represented by one

or four finger sequencing. The dependent task was also a manual sequencing task It was

hypothesized that if structural interference was primarily responsible for depression of

performance, the motor interfering task would have a greater detrimental upon the

dependent task than the vocal interfering task. Alternatively, if capacity interference is

implicated, the more difficult tasks should produce the highest level of interference

regardless of the apparent potential for structural competition. Rodney (1980) observed

significant interference effects arising from both structural and capacity factors.

The work of Rodney (1980) thus provides no resolution of this issue, indeed one

should not presume that any delineation should be made. Once again attempts at

classification are precluded by obvious contextual dependencies. Similarly, the dual task

paradigm can provide little that explicates the functional nature of the lateralized system, at

least with respect to motor control (Bryden 1982). Bryden is probably misguided in his

assumption that asymmetries are not expressed in "one shot movements", indeed it is difficult to visualize the constitution of such a movement. As Bryden himself realizes

"movements in a sequence might be considered as a structured series of smaller motor

elements or features" (1982, p. 120). Every movement proceeds in a manner which at some

level can be described as sequential.

Albeit expressed in the unfortunate lingua kanca of current motor control, Bryden's

reflections are insightful. Posing the question of, what aspects of a movement series

exhibits left hemisphere "control", The conclusion is drawn that : the left hemisphere might be crucial for selecting and stringing the motor features together: The left hemisphere could be seen as a master programmer. Alternatively, producing a series of movements also requires on-line monitoring at some level of the current position of the limb ... The left hemispheric system, then, might be responsible for this on line feedback monitoring (Bryden, 1982, p. 120).

3 7

Page 52: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Bryden concludes that the resolution of this issue lies ahead, it is the case however that

there is no issue as such, if resolution is required it is of the manner in which these

potential processes coexist and transact. What seems certain however is that the dual task

paradigm can provide few of the requisite tools. Clearly explanations in terms of the

assignation of processing "space" for somewhat arbitrarily selected concurrent tasks in

which there is competition for capacity, can reveal little of the situation which pertains for

normal goal directed actions which, although potentially, comprising the same task

subcomponents, may impose few of the same artificial constraints.

5.3 APRAXIA AND RELATED DISORDERS

Some elementary support for the view that left hemisphere adopts the role of "motor

programmer" is provided by clinical evidence arising from experimental manipulations and

from case studies of apraxic conditions. The need for considerable caution in interpreting

these studies arises independently of the general problem of extrapolating from clinical

cases which was highlighted in section 2.1. Although there seems to exist a strong

correlation between indications of perceptual asymmetries derived from "normal" and

clinical studies, this correspondence is notably absent when comparisons are made with

regard to motor performance (Bryden 1982). It is unlikely that the two sources of evidence

are irreconcilable, nevertheless, when generalizing on the basis of clinical studies, some

restraint is clearly prudent.

The clinical l i teram does at least have the virtue of providing further confirmation

that asymmetries in motor performance are not solely accountable to anatomical

considerations. A series of studies, initiated by Wyke, demonstrated that the effects of

unilateral brain damage were not symmetrical with regard to a variety of motor tasks (e.g.,

Wyke, 1966, 1967, 1968, 1969). Whilst, in these studies, the preponderance of crossed

anatomical pathways appeared to account well for the effects of right hemisphere damage,

producing deterioration of left hand performance, equivalent disruption of the left

hemisphere resulted in bilateral decrements. This work provided the impetus for a further

series of studies conducted by, in particular, Kimura (e.g., Kimura & Archibald, 1974;

Kimura, 1977; Mateer & Kimura, 1977). It appeared from these experiments that though

patients with either left or right hemisphere damage had few problems in producing single

hand postures, those with left hemisphere trauma experienced considerable difficulty with

the production of sequences of those postures (Kimura & Archibald, 1974). Bilateral

depression of the ability to perform motor sequences, in association with left hemisphere

damage was also revealed by Kimura (1977).

Page 53: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

It has also been demonstrated that this disruption applies not only to the brachial but

also to the oral musculature (Mateer & Kimura, 1977), leading the latter author to suggest

that the left hemisphere controls "sequences of movements" and that this side of the brain

contains "a system for accurate internal representation of moving body parts, important for

the control of changes in the position of both oral and brachial articulators" (Kimura, 1979,

p. 197). This position then closely equates with that of Lomas (1980). Certainly, one may

justifiably conclude that an intact left hemisphere is important for the generation of the

movement series designed by these workers. This does not entail that the role of the left

hemisphere in movement mediation is singularly that of movement programming, neither is

it clear, the extent to which the production of postures does or does not consist of

movement transitions and sequences. The level of analysis merely seems convenient.

The study of apraxia, generally considered to pertain mainly to the purposeful

generation of gestures, has provided what are potentially converging perspectives on the

role of the left hemisphere in movement organization. In concluding their historical review,

Faglioni and Basso (1985) note that most contemporary accounts of the praxic condition

afford a prominent role to the left prefiontal area, which may mediate "motor commands"

traveling to both sides of the body. By this viewpoint, it is prior to movement of limbs on

the left side of the body that commands are transmitted, h m the left prehntal area, via the

corpus callosum to the right premotor area and ultimately to the right motor area.

Alternatively, it has been suggested, that for right sided movements, commands are

dispatched directly to the left motor area (Faglioni & Bassi, 1985). This somewhat

restrictive explanation is itself inconsistent with a considerable number of case histories and

provides few details of the manner in which the relative contributions of "feedback

processing" and "movement programming" are sensitive to task demands.

The problems of extrapolating fiom clinical studies are more general, as Bernstein

shrewdly commented, almost five decades ago, The understanding of motor co-ordination, like many other scientific goals, has been achieved by a negative method - through observation of the phenomena of lack of co-ordination - and has been only gradually enriched by the accumulation of observations on pathological movement. Like all knowledge acquired by negative means it has constantly suffered, and suffers at present, h m the absence of accurate determinations (Bernstein, 1984, p. 213).

5.4 THE LEFT HEMISPHERE AS A "FEEDBACK PROCESSOR"

The view that the left hemisphere is uniquely specialized for the processing of

feedback information is itself not without support. Using a procedure differing somewhat

from that of the traditional dual task manipulation, Sussman, and his co-workers in a series

Page 54: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

of studies (Sussman, 1971, 1979; Sussman & MacNeilage, 1975; Sussman & Westbury,

1978), has marshalled evidence which suggests that, not only may feedback control be

strongly implicated as a basis for motor laterality, but also that data which purportedly

demonstrates a left hemisphere advantage for movement programming may bear

reinterpretation.

The experiment employed by Sussman (1971) involved auditory tracking. Subjects

were required to match an electronically generated tone, of which the frequency was under

subject control, presented to the left or the right ear, to a target tone of varying frequency

which was presented to the subject's other ear. Individuals were provided with one of two

alternative means of controlling the "cursor" tone, either via a transducer responsive to

lateral tongue movements, or directly using the right hand. In the condition in which the

"mouth controlled cursor was presented to the right ear and the target to the left ear, a

greater degree of accuracy was observed than when the cursor was presented to the left ear

and the target to the right ear. In contrast, when the tracking was performed by the right

hand, no significant difference by ear was observed. It was hypothesized that the effect of

ear was associated with factors relating to motor control of the cursor. This appears

plausible, as the target tone, and presumably the target analysis, were the same for both

hand and "articulator" tracking. In an explanation which appears, only superficially,

analogous to that forwarded by Lomas (1980), it was suggested that both the pursuit task

and speech articulation involve the comparison of a controlled auditory output to an

"acoustic standard" and an "ability to control the motor system in terms of acoustic

consequences, presumably with concurrent use of somatic sensory information" (Sussman

& MacNeilage, 1975, p. 146).

As Bryden (1982) comments of the Sussman position, it is a central tenet that

feedback is evaluated in terms of a superordinate goal, ongoing motor activity is to be

compared to a standard. Indeed it is conceivable that the deficits witnessed in individuals

having suffered left hemisphere lesions, may arise from an inability to evaluate the relative

positions of elements within a sequence rather than a failure to generde sequences per se

(Bryden, 1982). Again it must be stressed that during ongoing movement in normals, both

processes are typically occuning, the respective involvement of each being significantly

influenced by task demands.

Although predominantly employed to examine the relationship between the

processing characteristics of the left hemisphere and the execution of motor performance,

the dual task paradigm may, with some caution, be used as a means through which the

features of right hemisphere processing may be discerned. As Hellige and Longreth (198 1)

point out however, the interpretation of lateralized motor interference is somewhat more 40

Page 55: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

convoluted when it is the characteristics of the right hemisphere which are of interest.

Whilst it may be the case that the right side of the cortex has a unique competence for the

processing of "visuospatial" information, this superiority may well be masked by the nature

of the output measures, for example, responses taking the form of vocalization or of a

number of expressions of manual proficiency, may be subject to a large degree of

mediation by the left hemisphere.

In the second experiment of a 198 1 study, Hellige and Longreth required that their

subjects perform in what were essentially two conditions. In the first, individuals were

required to simultaneously tap a key with the index finger of either the left or right hand,

whilst, in the other hand, handling blocks in a way that apparently involved little cognitive

processing. Tapping rate was depressed equivalently for each hand. This may be

interpreted as indicating that the motor output requirements of the block manipulation,

putatively requiring some left hemisphere involvement, may have swamped any effects due

to the visuospatial nature of the task. Direct support for this interpretation is provided by

data arising from the second condition. When a spatial task including both cognitive and

motor components, the Block Design test of the Wechsler Intelligence Scale, was

substituted for simple block manipulation, there was greater disruption of left hand than of

right hand tapping. It seems the Block Design test required a degree of spatial processing

which was sufficient to be manifested as a depression of the rate of left handed tapping.

In a similar vein, there is evidence to suggest that visual detection tasks (analogous

in a very strictly limited sense to the Block Design test used in the Hellige and Longreth

(1981) study) exerts an asymmetrical influence upon motor output. Beaton (1979) had

subjects perform a bimanual sorting task comprising two individual components, one of

which was consistently the index of overall performance. Proficiency on this component

(nut sorting) was depressed to a greater extent when the yisual detection target was

projected to the right hemisphere. Detection to the left hemisphere did not

disrupt manual performance. Summers and argued that the movement

sequencing tasks, frequently utilized in this paradigm, are subject to control by both

hemispheres, as finger sequencing involves both the localization of limb segments in space

and the ordering of movement subcomponents within a series. The implications of this are

wide ranging. As Todor and Smiley (1985) highlight, the vagaries between visually guided

and unseen movements outlined by Lomas (1980) may have arisen due to the absence of a

visuospatial component in the latter, it is conceivable that the need to employ an

"internalized spatial position system" had some direct influence upon the decreased rapidity

of movement sequencing. In the sections which follow, further reference will be made to

this issue. 4 1

Page 56: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 6

CHARACI'ERISTICS OF THE MOTOR OUTPUT

6.1 REASONS FOR CAUTION

In turning to Bashore's final factor (section 4.3), the motor output, little further

need now be said regarding the exigency of emphasizing the functional unity of the

perceptual and motor systems (e.g., Lee and Thomson, 1982), yet it remains the case that

the extent to which an asymmetry is expressed is highly task dependent and relies, in large

part, upon the nature of the motoric components of that task As has been illustrated, this

dependence has exerted a highly constraining influence on the definition of what, for some,

may constitute an adequate account of the underlying mechanisms (c.f., Lomas, 1980).

Consequentially, accompanying attempts to satisfy the appetite for the specification of

mechanisms or processing devices, there have been numerous ad hoc assignations of

functional properties or arbitrarily defined capabilities. The level to which these

pseudoassumptions may descend is well illustrated by the suggestion of Todor and Srniley

(1985) that in a certain task "one might expect the left hand to opt for a strategy that

optimizes its performance capabilities" (p. 3 14). It would perhaps be more profitable to

consider the manner in which the characteristics of the nervous system give rise to the

expressions of manual asymmetries which are so highly task dependent.

As a research endeavor this approach obviously requires consideration, not only of

the characteristics of the nervous system per se, but also highly specific examination of the

nature of the motor behaviour to which the activity of the nervous system gives rise. It will

be argued that this dual sensitivity is an initial requirement. It has been customary for

accounts of manual asymmetries to give a superficial and highly selective account of the

nervous system as a whole, which, as has been shown, may be described at the

phenomenological level as a unitary instrument subserving goal directed action, yet this

almost incidental consideration alters appreciably the nature of the interpretations to which

observations give rise. In the sections which follow reference will be made to an extensive

body of work which, when examined in view of known properties of the neuromuscular

system, requires significant reevaluation.

6.2 TAPPING TASKS

There have been a large number of recent studies which have employed tapping

tasks as a means of assessing the characteristics of manual asymmetries. Two varieties of

this task can be distinguished. In one instance, the trajectory of the tapping finger is highly 4 2

Page 57: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

restricted by, for example, attaching the finger directly to the tapping key (e.g., Todor &

Smiley-Oyen, 1987). There are as a result few accuracy demands and it is the speed of

tapping which is generally emphasized, though contemporary studies have also required

that subjects tap to specified frequencies. The other variety of tapping task is rather less

restricted, being more akin to a succession of aimed movements, and will not be described

at this juncture.

Traditionally, the primary dependent variable employed in this paradigm has been

the rather global measure of tapping frequency. Kimura and Davidson (1975) observed a

superiority for the right hand in terms of the rate of tapping, although Peters (1976) found

that this difference could be eliminated through extensive practice. It seems however that

the variability of left handed tapping, in terms of inter-tap interval (ITI) remained

significantly higher, even after 1300 trials, eliciting fiom Peters (1976) the less than

illuminating suggestion that the left and right hands differed in their mode of motor control.

Further work has confirmed that generally, on this task, the right hand taps more rapidly

and with greater regularity than the left (Peters & Durding, 1978, 1979a).

In something of an effort to expand upon his suggestion that manual asymmetries

arise fiom differing modes of control, Peters (1980) published a contentious three

experiment study which, in spite of what are manifestly fallacious conclusions, proved to

be a seminal study. The first experiment may be considered relatively insignificant in

producing an unconvincing illustration that asymmetries are not reflections of greater

strength for the right hand. This is somehow inferred from an indication of resistance to

fatigue.

In the second experiment of the series, a rather more sophisticated tapping

apparatus was used, permitting the evaluation of measures in addition to simple tapping

rate, specifically, the time taken to "reverse" a movement at the top and bottom of its travel,

and the period spent in the single up or down movements between reversals. The results

obtained appear to have indicated that, whilst a difference in terms of overall movement

duration and thus tapping rate was present, it was the portion of the movement in which

reversals occurred that represented the major contribution to this difference. This phase

Peters (1980) regards as the transition between flexor and extensor movements which, he

feels, reduces to the precision of "force modulation".

In the course of a third experiment, in which the maintainence of performance, in

terms of tapping rate, was presumed to require even greater precision of force modulation

(by further limiting the extent of digit excursion), it was hypothesized that the modified task

would lead to a proportionately greater decrement in left hand performance. The results

Page 58: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

indicated that the performance of the non-preferred hand did indeed decline to significantly

greater extent when this task constraint was imposed.

Whilst it may indeed be convincingly argued that it is apparent precision of force

modulation which differentiates the hands, the factors which give rise to this asymmetry are

less well appreciated by Peters. The contention that "peripheral factors are relatively

unimportant in producing between hand performance differences" (Peters, 1980, p. 70)

clearly contrasts markedly with views within "contemporary" physiology, for example,

Bernstein (1984) who in expressing aspects of his "circular principle of control" stressed

the necessity of examining the nature of the "sensory feedback connections" (p. 344). Peters' confusion perhaps arises from a misconception of the nature of the movements he is

investigating, considering them to be "too short for the direct involvement of sensory

feedback" (1980, p. 70).

It does appear however that there are no voluntary movements which can proceed

more rapidly than the speed with which some form of sensory feedback can be mediated

(Bawa, note 5). The fastest voluntary movements may only approach the frequency of the

physiological tremor, which, with respect to the digits, is approximately 10 Hz. Some

researchers have suggested that peripheral kinesthetic feedback loops can be completed in

as little as 25-50 msec (Dewhurst, 1967; Evarts, 1973).

There has been a tradition of considering the initial phase of a movement to be

"ballistic" and as such unaffected by sensory feedback (e.g., Welford, 1971). Apparent

support for this position has generally been provided by analysis of the

electromyographical (EMG) activity during movements. The archetypal triphasic pattern of

activity is composed of an initial agonist burst, followed by activity in the antagonist and

finally a further separate agonist agonist burst. In practice, this pattern is difficult to

achieve. It was generally held that "open loop" control exists during the initial portions of

the movement (up to 100 msec.), as perturbations or blocks to the movement were found to

have no effect upon the initial agonist f ~ n g , as revealed by EMG (e.g., Hallett, Shahani &

Young, 1975; Wadrnan, Denier, Geuze & Mol, 1979). Certainly, exclusion was made of

any potential role of visual feedback during this period. However, when target position

lights are displaced, in this portion of movement, there occurs a very rapid modulation of

EMG, leading to the suggestion that a "closed visual loop" of some nature may be

operating (Gielen, van den Heuvel & Gon, 1983; c.f., Young, 1987).

The changes in the initial agonist firing pattern which had been seen to accompany

increased resistance to movement (Brown & Cooke, 1981; Lee, Lucier & White, 1981)

have been dismissed as merely reflexive and having no contribution to unconstrained

visually guided movements (e.g., Todor & Smiley, 1985). It has recently been suggested 4 4

Page 59: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

however that long latency EMG responses are not only compensatory but permit the

alteration of ongoing control in light of peripheral conditions and in turn reflect the presence

of routes along which sensory information may flow to central structures (Requin, Semjen

& Bonnet, 1984).

Peters (1980) postulated rather that tapping: depends on central preprogramming (Schmidt, 1975) and any role of sensory factors in the guidance of such movements must be restricted to the evaluation and adjustment of the central motor program (p. 70),

and continues to maintain that feedback is utilized through "occasional probing" rather than

on a continuous basis (Peters, note 1). The work of Hary and Moore (1985) is cited as

partial support for the view that probing may occur where the speed of movement precludes

"continual sampling". Even if it were the case that voluntary movements could proceed this

rapidly, controlled motor output in the apparent absence of sensory input does not imply

that normal movements proceed in this fashion (Agarwal & Gottlieb, 1984). The point is

made succinctly by Reed (1982), who in restating Bernstein's position outlines: Bernstein suggests that the animal is in continual &-equilibrium with its environment, requiring that it not to stimuli, but rather that it all the time and that it constantly evaluate its actions with respect to ever changing current conditions, while at the same time modulate its activities so as to meet its needs and goals within the environment (p. 108).

It is thus seems that it is only on the most fragile basis that Peters (1980) may question the

role of sensory feedback in contributing to manual laterality effects and conclude that: the most likely source of asymmetries is in the process whereby the movement is preprogrammed and whereby the selection and activation of appropriate neurons occurs (p. 7 1).

What appear to be ballistic movements rnay,in turn, seem preprogrammed, yet even these

movements are sensitive to the "most recent peripheral states of the system" in a manner

which permits not only load compensation but also modulation of the "central command"

(Agarwal & Gottlieb, 1984, p. 568).

Peters major contribution with regard to the evaluation of movement asymmetries is

likely to have been the delineation of movement phases within tapping and the examination

of the extent to which asymmetries are expressed in these respective portions. From a

number of additional, well controlled, studies conducted during the past decade, a

consistent pattern of results has emerged. The more rapid rate of tapping for the preferred

hand is generally associated with shorter periods during which the tapping key is

depressed. That is, less time was spent in the phase of movement in which reversals of

movement took place (Todor & Kyprie, 1980; Todor & Smiley-Oyen, 1987), additionally,

there was less variability of the IT1 (Todor & Kyprie, 1980; Todor, Kyprie & Price, 1982).

The observation that it was differences of variability in the interval between force peaks

Page 60: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

which reached statistical significance, rather than the differences in the variances of the

more global Ill (Todor & Smiley-Oyen, 1987) appears to lend partial support to the notion

that, the left hand is more variable in its regulation of force, and for Peters' (1980) view

that this hand can less precisely modulate force.

It is unfortunate that virtually all successive attempts to provide some explanation of

these results have included, from the onset, erroneous assumptions regarding the role of

sensory input, including suggestions that the latency of a movement reversal is "below the

minimal time estimated for the use of peripheral feedback" (Todor & Smiley, 1985, p.

3 16). This has given rise to conceptualizations of the bases of manual asymmetries which

are not only insensitive to the characteristics of the nervous system but also embrace a

confused notion of the presumed relationships between the components of that system.

Thus, "the left hand is less adept in establishing an effective framework around which to

regulate successive directional reversals" (Todor & Smiley, 1985, p. 316). Elliott (note 2)

has been somewhat more circumspect in proposing that the right hand advantage arises

from a superiority in "parameterizing" movement.

Although there has been a failure to elicit O ing asymmetries in a small proportion P of studies (e.g., Flowers, 1975), the majority of studles seem supportive of the view that

tangible differences do exist. What has been viewed as variations in force modulation

(Peters, 1980) or in regulation (Todor & Kyprie, 1980) arising from some aspect of

preprogramming, has also been considered as due simply to differences in the "intrinsic

variability or noise in the production of force time patterns" (Annett, Annett, Hudson &

Turner, 1979, p. 647). This position is descended directly from the Schmidt, Zelaznik and

Frank model of 1978 which encapsulates the prediction that "variability in force amplitude

varies inversely with the square of movement time and the variability of force duration

varies directly with movement time" (Annett et al, 1979, p.647). The task employed by

these authors was substantially different from the highly restricted tapping tests.

Individuals were required to transfer pegs, independently with each hand to appropriate

locating holes in a proximally placed board. Using a film record of performance, something

akin to a kinematic analysis was attempted though, as the data was sampled at 40 frames

per second, the results should be approached with some caution. Gross analysis revealed

that the preferred hand could more rapidly perform the movement series. More detailed

analysis of the film record indicated that the differences occurred primarily during the

"positioning" element of the movement rather than the "transport phase". Specifically, the

non-preferred hand more frequently missed the target hole, making on average 50% more

corrective movements. Indications from the patterns of latencies suggested to Annett et al.

(1979) that the corrections were themselves conducted on the basis of a "kinesthetic 4 6

Page 61: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

feedback loop", and that the duration of these corrections did not differ significantly

between the hands. It seems that in the Annett et al. study at least, the non-preferred hand

was simply more variable. The movements to the target itself were assumed to be "open

loop" and were made at the equivalent rate for each hand. It was rather the accuracy of

these movements which diff& Whilst, as noted, the conviction that movements to the

board were open loop was misguided, it is of interest that Annett et al. (1979), following

Schmidt et al. (1978), consider that the variability arises from the characteristics of the

entire system, rather from neural, muscular or mechanical properties. This, however,

provides little illumination of how the variability arises or is asymmetrically expressed.

More recently, Peters (1987; note 1) has implied that "attention" may play an intervening

role in the expression of asymmetries and that this factor may be more important than the

variability of output as such.

One persistent problem for those seeking to examine the relative distribution of

manual proficiency in left and right handers is that members of the former population have

generally had more experience in performing movements with the non-preferred hand in

comparison to their right handed counterparts. One way in which this limitation has been

overcome is through the use of tasks which reduce the importance of practice levels, an

example being bimanual tapping. Although, as has been described, the maximal rate of

tapping varies between the hands, along a number of dimensions, examination of tapping at

submaximal rates reveals few such differences (e.g., Wolff, Hurwitz & Moss, 1977). It

appears to be the case however that when submaximal tapping for each hand is combined in

a dual task, asymmetries are once more revealed. In a "2: 1 task" in which one hand

completes two taps for one tap made by the other hand, individuals perform in superior

fashion when the preferred right hand makes the two taps (Peters, 1985, 1987). This

benefit is evidenced by tapping which is both more rapid and more regular. For Peters

(1987) this enhancement arises as a consequence of "a tendency of right handers to direct

attention preferentially to the right body half" (p. 97). In summarizing, Peters (1987)

considers that the essence of this bimanual task is the organization of movement into

"rhythmically different concurrent sequences" concluding that "both in the perception and

production of different temporal sequences there is the problem of how to focus attention

on the component parts of the sequence" (p. 98). This is not however a problem for the

nervous system.

6.3 THE NON-ROLE OF ATTENTION

The view that the differential distribution of attention may account for hemispheric

asymmetries in general has appeared previously in a variety of guises, most notably 47

Page 62: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Kinsbourne's "bidirectional, negative interaction" model (e.g., 1970, 1974a, 1974b). The

essential characteristic of Kinsbourne's model is that a mutual inhibitory balance exists

between the hemispheres with respect to attention or orientation and to consummation or

the motor act. A central balance or bisymmetry is taken however to be an improbable state,

and is "specifically programmed only if functional pressures make it necessary"

(Kmsbourne, 1978, p. 11). Thus, if an individual has "language ability" lateralized in the

left hemisphere, preparation for "verbal activity" will lead to "neuronal activation" of the

left hemisphere, resulting in a rightward attentional bias (Kinsbourne, 1978). This, it is

presumed, explains the asymmetries evident in both dichotic listening and tachistoscopic

presentations. In similar fashion, it is maintained that manual asymmetries arise as

bisymmetry is functionally disadvantageous. Rather than considering that the magnitude of

the asymmetries are dictated by the extent to which a function is lateralized, Kinsbourne

argues thusly: The extent to which attention swings contralateral to the more active hemisphere is determined not only by where the active processor is lateralized, but also by how hard it is working. How hard it is working is in turn deterrnined by how difficult the task is and how willing and able the subject is to rise to the challenge of the task. (p. 10).

This at least has the merit of encapsulating a sensitivity to the task and context specific

constraints, though again one must confront the problem of how "active processors" may

be reconciled with what appear to be examples of mutual inhibitory balances in simple

neural systems. There are more immediate problems for this formulation: there now seems a consensus that, although attentional factors undoubtedly play some role, they are certainly not the only factors responsible; strong asymmetries can be demonstrated even when attentional components are minimized or eliminated. In addition there have been some difficulties in replicating the original Kinsbourne data. (Allen, 1983, p. 83).

The pervasive nature of spatial compatibility effects offers a potent indication that to

maintain that attention is predominantly channeled to the right side of the body is severely

shortsighted As Peters (1987) acknowledges, there is really no clear indication of that to

which "attention" refers. In spite, or perhaps because of, this obvious limitation, there has

been a considerable volume of research, conducted primarily by Honda (e.g., 198 1, 1982,

1984) which has examined the issue of whether vagaries in the distribution of attention may

account for the observed superiority of the preferred hand In order to fashion some

appreciation of the context in which these formulations arose, it will prove efficacious to

briefly review the background to Honda's work.

It has for some time been apparent that the transaction between the organism and its

environment dictates the form of the percept to which the activity of the organism gives

rise. It is important to recognize that, as transactional, not only does the activity of the

Page 63: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

organism, relative to its environment, structure perception, but in addition, the changing

characteristics of the environment relative to the organism alter the behavioural mechanisms

through which this perception takes place.

One explicit illustration of this may be derived from the research generated by

Rashbuss's (1961) conclusion that smooth pursuit eye movements are governed by both

the direction and velocity of "target" movements, whilst saccadic eye movements are

sensitive to the position of a target. Festinger and Canon (1965) undertook a series of

experiments which provide some illumination of the significance of this disposition. The

studies were conducted in a completely dark room. In one condition, a target light appeared

briefly within the subject's visual field, subsequently the individual was required to point to

the position at which the light had appeared. A saccadic eye movement was required to

fixate the target in this instance. In a second condition, the target light appeared and moved

slowly across the visual field before disappearing, some form of tracking was thus

required. Subjects were, in each case, required to indicate, by pointing, the final position of

the target. Performance when subjects had directed a saccade to the target was superior to

that when the position had been tracked.

By way of explanation, it was proposed that the superiority of saccadic eye

movements was due to the availability of efferent "signals" associated with the oculomotor

system. These concern the position of the eye within its orbit and were presumably utilized

in a manner which provided some indication of target position. In contrast, it has been

assumed that the use of the extraocular muscles responsible for tracking movements, does

not give rise to information which is amenable to the generation of a conscious perception

of eye position (Brindley & Morton, 1969). It should be noted however, that in order to

exert an influence upon the control of overt responses it is not necessarily important that

consciousness as such is invoked.

On the basis of observations that a superiority for the preferred hand was evident

only when the motion of the hand was visually monitored, Honda (1982) proposed that the

movement of the preferred hand is itself intimately associated with the oculomotor control

system. As an initial objection, the original premise is clearly inappropriate (c.f., Lomas,

1980), and as will become manifest, the conclusion is no more convincing.

In the first experiment of the Honda (1982) study, subjects were required to make

bimanual movements to symmetrically placed targets. Eye movements were recorded by the

EOG technique, whereby, electrical activity was monitored through electrodes applied to

the lateral, and upper and lower sides of the eyes. The findings indicated that, although

individually moved their eyes rightward, there was no between hand difference in

performance. Indeed, in many instances there was a complete absence of eye movements, 4 9

Page 64: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

the nature of the task was such that subjects were able to successfully complete the

bimanual movement without recourse to eye movement. Theorists have previously outlined

the possibility that an elevated tendency to make rightward eye movements may be due to

reading habits (White, 1969). It is then possible that the increased frequency of rightward

motions was actually due to .this overlearned disposition. This issue should obviously be

resolved by means of a controlled cross cultural examination.

In order to go some way toward dealing with this issue, Honda (1982) included a

second experimental series in which target sizes were reduced relative to those used in the

first experiment. It was proposed that rightward eye movements, if indeed due to reading

habits, would be more prominent if digits were presented as targets and no aiming

requirement was included (Honda, 1982). The logic of this was fuzzy to say the least, there

seems no reason to regard the digits as anything other than targets in the previous sense,

certainly they did not occur in a context bearing any more resemblance to reading than the

aiming task. It seems that a more appropriate question would have been whether the

rightward shifts in aiming tasks are due to reading habits. The results arising from this

second manipulation indicated a rightward superiority for the digit task, though of a

magnitude smaller than that for the bimanual aiming task. Honda (1982) somehow

interprets this as demonstrating that a rightward superiority of eye movement was a feature

specific to tasks involving hand movements rather than simply looking at displays. A statistically significant between hands difference was observed, the performance of the

preferred right hand being superior to the left. Honda (1982) states that the implication of

this finding is that "subjects prefer to monitor the movements of the right hand than the left"

(sic) (p. 5 lo), and in turn that right hand movement control depends more on visual

feedback than the left. In view of the indeterminate nature of the rightward shift, the

conclusion that some preference is involved appears quite erroneous. It was further

postulated that the right hand's better performance in bimanual aiming tasks is based upon

the right hand's "superiority" of eye movements, yet this seems an almost trivial confusion

in an account which can suggest that, with respect to bimanual movements, "it seems quite

redundant to receive sensory feedback from both hands" (Honda, 1982, p. 512).

Nevertheless it may well be the case that the habitual rightward shift makes available, more

consistently, information regarding the right side of visual space, which in view of the

aforementioned spatial compatibility effects may contribute to a general superiority for the

right hand, as the hand most often also located in the right visual space. Similarly, it is

conceivable that the left hemi-field superiority witnessed for brief presentations of particular

types of stimulus material (see section 2.3), and most clearly revealed when required

responses are simple, short duration, single joint movements, may in turn be obscured 5 0

Page 65: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

when responses are longer duration aiming movements extending into extrapersonal space.

In the latter instances, it would be supposed that, movements to stimuli presented to the

right of fmation would be favoured by the predominant rightward shift. It is not

immediately clear at present the effects this would have on behavioural indices such as

reaction time and movement ~ e .

Honda's (1982) suggestion that not only is the movement of the preferred hand

preferentially monitored but also that it is associated intimately with the oculomotor control

system was examined in rather more detail in a subsequent study (Honda, 1984).

Employing what was essentially the experimental paradigm utilized by Festinger and Canon

(1965), consideration was given to potential between hand differences in the magnitude of

the constant error of pointing responses. This factor was considered within the two

conditions in which subjects made either saccadic or smooth pursuit eye movements. It was

observed that for both hands, saccade eye movements were associated with superior

performance. Honda (1984) unfortunately confuses the level of statistical significance with

the nature of the effect, although there was no statistically significant pointing hand by

stimulus condition interaction, the author is led to claim that "the effect of the eye

movements on manual pointing is prominent on the preferred right hand than on the non-

preferred left hand" (p. 75). Clearly however, the prediction that the differential effects of

the two types of eye movements would be evident only for the preferred hand is not

supported. Honda (1984) continues to promulgate erroneous conclusions based on the

misinterpretation of the analysis, claiming "the left hand seems more independent of eye

position information than that of the right hand" (p. 86). In a spiralling confusion, Honda

assesses there to be a problem, suggesting that "eye position is not a dominant cue for

spatial localization of the left hand" (p. 86), and thus that there ought to be a search for the

missing dominant one. The explanation proffered seems quite independent of the pattern of

results obtained. It cannot be concluded that the behaviour of the left hand is not in some

way sensitive to the type of eye movements made. On the contrary, Honda's (1984) results

clearly indicate that saccadic eye movements were associated with superior performance by

the left hand. ! Of some interest was the observation that a statistically significant difference in

terms of the variable error of the pointing response was composed of a greater variability

for the right m. The magnitude of this difference appeared to be sensitive to the visual

half field in which the stimulus was presented. There was no obvious difference in variable

error between target presentation conditions.

It remains the case that conceptualizations of what constitute attentional asymmetries

remain so ill defined as to be of little practical worth. Similarly, there is no empirical 5 1

Page 66: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

evidence, nor a priori reasoning to suggest that one should concur with Honda (1982) in

concluding that the right hand is preferentially monitored. However the view that manual

asymmetries result from a differential efficiency in the use of visual monitoring (Honda,

1982) has, in a number of manifestations, garnered considerably more support. In the

sections which immediately follow, attention will be given to those holding the perspective

that the magnitudes of manual asymmetries vary as a function of the differential efficiency

with which the cerebral hemispheres deal with feedback information, and in particular

visual feedback

Page 67: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 7

THE ROLE OF VISION IN THE REGULATION OF AIMED MOVEMENTS

7.1 A MINIMUM PROCESSING TIME FOR VISION?

It was Woodward who in 1899 provided perhaps the first quantitative support for a

view which might always have been intuitive, that the preferred hand performs rapid aim

movements both more rapidly and more accurately than the non-preferred hand.

Woodworth's subjects performed a series of line drawing movements either with their eyes

open or eyes closed, providing, in addition, one of the first rudimentary manipulations of

visual feedback. Perhaps contrary to expectations, it seemed that movements of particularly

short durations were unaffected by the presence or absence of visual information, leading,

in turn, to the suggestion that there was some minimum time required for the utilization of

information of visual origin.

Since this time a variety of authors have attempted to distinguish two distinct phases

within such movements: a ballistic transport phase during which the aiming hand is brought

to within the vicinity of the target, and a relatively short second phase permitting the

accurate final positioning of the hand (Pelisson, Prablanc, Goodale & Jeannerod, 1986).

The practical utility of this, merely descriptive, dissociation has had the unfortunate

consequence of sanctifying the implied physiological reality of the "motor program", as a

necessary and sufficient condition for the control of single movements. This rather

simplistic perspective has been portrayed most explicitly by Keele, in 1968, conceiving that a motor program may be viewed as a set of muscle commands that are structured before a movement sequence begins, and that allows the entire sequence to be carried out uninfluenced by peripheral feedback (p. 387).

Whilst it would require a considerable digression to provide any substantial coverage of the

"centralist" versus "peripheralist" debate, it remains sufficient to note that Keele's proposal,

as received, was somewhat less than cautious. Although it is impossible to provide any

substantial justification for a view which, although perhaps only an inelegant exposition of

the perceived need for the motor program as an explanatory construct (c.f., Requin,

Semjen & Bonnet, 1984), clearly belittled a large corpus of physiological research, it is

enlightening to examine the research which was conjunctive with Keele's 1968 review.

Most central and precipitative was the work leading to the publication by Keele and

Posner (1968) of an estimated minimum time for the processing of visual information.

Subjects were trained to move a hand held stylus approximately six inches to a small target,

taking either 150,250,350 or 450 ms to do so. On certain trials, randomly determined,

visual feedback was removed upon movement initiation, the mom lights were 5 3

Page 68: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

extinguished. Performance was assessed in terms of the proportion of occasions on which

the target was "missed in each condition. Predictably, the probability of missing decreased

with increasing movement duration, importantly however, an advantage for conditions in

which visual feedback information, of hand and target position, was available, only

occurred for the longest three movement durations. When aiming movements were

performed in the 150 ms condition (actual average movement time was 190 ms) there were

no differences in performance between the two illumination conditions. As vision of the

hand and target appeared, superficially, not to facilitate movement control for movements

of 190 ms or less, Keele and Posner (1968) concluded that this was the minimum time

required to usefully incorporate visual feedback.

There are, however, a number of procedural considerations which constrain the

universality of these findings. As the potential availability of feedback was randomly

determined, it may have proved useful for subjects to adopt a strategy whereby it was

assumed that the movement would be made without visual feedback. This may have served

to diminish the apparent magnitude of the facilitation effects of visual feedback, and

purportedly, though less obviously, contributed to a "delay in processing" for No-Vision

trials (Zelaznik, Hawkins, & Kisselburgh, 1983).

These latter authors also suggest that the specification of target movement times

may have shifted subject's attention form considerations of accuracy. It is difficult to see

however that target, movement time bandwidths favoured initially by Zelaznik et al. (1983)

provide anything which more closely resembles an "ecologically valid" action goal than a

set movement time. Conventionally, when movement time appears salient for appropriate

task completion, it is in circumstances in which the temporal and spatial coordinates of the

body or of a body segment must be made coincident with the coordinates of an external

entity. It is unlikely that movement time per se is of interest to the organism (c.f., Lee,

1980). In natural reaching movements, were the emphasis is on accuracy, movement time

may more appropriately be examined as a dependent variable (Jeannerod & Prablanc,

1983). There are alternative and less artificially constrained ways in which the relative

contribution of visual information to task completion may be examined (see Section 7.2). In a more contemporary examination of this general issue, Zelaulik, Hawkins and

Kisselburgh (1987) have suggested that it is not the minimum time to process visual

information which has been sampled, but rather, the "minimum average momentum that the

visual feedback control system can overcome" (p. 183), reasoning that the time required to

complete a correction will vary as a function of the of the limbs resistance to perturbation

and thus as a function of its momentum and, for these purposes, velocity. Zelaznik et al.

examined this issue by considering combinations of three movement durations, 200,400, 5 4

Page 69: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

and 600 ms, and three movement distances, 10,20, and 30 cm, yielding three possible

combinations for which the average velocity was 50 c d s , specifically 10-200,20-400,30-

600. Once again the use of movement time goals creates interpretative problems,

additionally, in view of the authors prediction that resistance to perturbation is a function of

momentum, one would have to question the use of average velocities rather than peak or

instantaneous velocity. hde& the results obtained by Zelamik et al. (1987) provide no

support for the speculation that required correction time varies as a function of limb

momentum, observed benefits in terms of spatial accuracy, for the 50 c d s combinations

varied as a function of movement time.

As noted, consideration should more importantly be given to the manner in which

the time required to make a correction may vary as a function of instantaneous velocity and

thus instantaneous momentum. The required manipulation may now, in principle, be

achieved through the use of microcomputer based motion analysis systems. It is possible

from these systems to obtain an, on line, estimate of the position of a limb segment in three

dimensional space. By referencing the final target location in terms of some coordinate

system and through "on line" computation of changes in displacement over time, it should

be possible at any instant to establish both "instantaneous velocity" and the time to target

contact. Through the use of appropriate external operators, visual feedback may be

removed at a predetermined peak or instantaneous velocity or at a predetermined estimated

time to contact.

Returning directly to the Keele and Posner study of 1968, a further, and

potentionally critical, limitation was the use of the probability of missing the target as the

central dependent measure. It is certainly the case that this is a rather insensitive measure,

certainly in comparison to spatial accuracy. The use of response measures of greatly

enhanced sensitivity, in a series of subsequent studies, has precipitated continuous

downward revision of the estimates of minimum visual feedback processing time from the

190 to 260 ms range suggested by Keele and Posner (1968).

An initial experiment conducted by Carlton (1979), which whilst not directly

manipulating visual feedback as such, was one of the first to employ a rudimentary

kinematic analysis as a means of demonstrating that "discrete" movement corrections could

be made more rapidly, in the basis of visual information, than the 190 ms limit imposed by

Keele and Posner (1968) or the 290 ms time later suggested by Beggs and Howarth

(1971).

The need to fashion some manipulation of visual feedback has spawned a number

of novel and innovative procedures. Using a closed circuit camera system, Smith and

Bowen (1980) delayed visual feedback during an aiming movement. Movement durations 5 5

Page 70: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

ranged from 150 to 450 ms, across all movements, feedback delayed by 66 ms was

associated with an overshooting of the target which was not present in a no delay

condition. That this disruption was observed for even the most rapid movements

(approximately 160 ms) lead Smith and Bowen (1980) to conclude that the processing time

was actually less than 100 ms

Carlton (1981a) also using aimed hand movements, noted changes in the kinematic

profile which occurred within 135 ms of the appearance of the individual's hand from

behind an occluding screen, providing, it seems, converging support for the revision made

by Smith and Bowen. In a second experiment, Carlton (1981b) provided an indication that

the relative importance of vision of the hand and vision of the target may, in turn, be highly

task dependent. Subjects were required to make, short amplitude, aiming movements using

a hand held stylus in five conditions of visual feedback; ambient lighting present, ambient

lighting removed, vision of the target only, vision of the stylus only, and vision of both the

target and the stylus in the absence of ambient lighting. In terns of procedure, there were a

number of associated limitations, a movement time goal of 330 rns was established and

performance was scored in a manner similar to the Keele and Posner (1968) study, as a

proportion of target misses. Somewhat predictably, the poorest performance was for I

movements made in the complete absence of visual infoxmation. A similar level of

performance was witnessed for instances in which only target information was present. On

the other hand, movements made with vision of the stylus only, with vision of the target

and stylus, and with ambient lighting present were performed equivalently. Whilst the

results of this study do not speak directly to the issue of feedback utilization latencies, it

does provide evidence, that ir, this instance, useful utilization of visual information was

limited to assessing the position of the stylus and, by implication the hand, relative to

external space, rather for comparison of the relaqve positions of stylus and target.

Information regarding the position of the target alone proved no more useful than no visual

information whatsoever.

Issues pertaining to the relative importance of visual information emanating fiom

various sources, in relation to task specific constraints, will be examined in more detail in

section 7.2. At present, it is sufficient to note that estimations of the time required to

usefully incorporate information of a visual origin will vary as a function of the nature of

that incorporation within the context of a goal directed act. Similarly, the overt behavioural

consequences of this incorporation may, in turn, vary considerably with task demands

(c.f., Pelisson et al., 1986). If, on the one hand, it may be proposed that the time taken to

usefully employ visual information is highly task dependent, the reverse of this argument

might be used to as forcefully suggest that, in particular, apparently short latency feedback 5 6

Page 71: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

processes (e.g., Smith & Bowen, 1980; Carlton, 1981a) may merely be due to procedural

artifacts.

In an attempt to verify that, for movements of short duration, visual feedback can

"aid motor control via processes not associated with intermittent error corrections" and to

demonstrate that the substance, if not the magnitude, of these effects was robust, Zelaznik

et al. (1983) performed a series of experiments within the Keele and Posner (1968)

paradigm which to some extent removed the procedural ambiguities associated with the

initial study. The first of four experiments addressed three of the potential limitations of the

Keele and Posner procedure; in place of the rather insensitive dependent measure

"proportion of target misses", the spatial accuracy of movements was monitored, as

previously mentioned, movement time bandwidths were used in place of movement time

goals, and additionally, trials occurred in blocks of visual feedback present or visual

feedback removed for which subjects could presumably then select the "optimum strategy"

for each condition, or within blocks in which, like the original study, the availability of

feedback was uncertain. The results indicated that the exclusive use of "uncertain

conditions" in the Keele and Posner (1968) study may have directly served to reduce the

effectiveness of the visual feedback manipulation. Zelaznik et al. obtained indications that

visual feedback processing times may be in the region of 100 ms Potentially however, the

depressed performance in conditions in which visual feedback is removed upon movement

initiation may be due to the sudden change in the visual environment as ambient lighting is

removed rather than due to the absence of visual information per se. In a direct attempt to

examine this possibility, Zelaznik et al. (1983, exp 2) reversed the protocol through making

ambient light and thus visual information available upon initiation of the movement. A pattern of results paralleling those for experiment 1 were obtained, leading the authors to

conclude that the "critical factor in determining accuracy is the presence of vision during the

movement, not a constant environment " (p. 227).

A third experiment dealt with the possibility that the benefits seen in the presence of

visual information might be due to some unknown artefact, through an attempt to establish

some movement time below which visual information no longer appears beneficial. The

results of experiment 3 indicated that movements of 70 ms duration appeared unaffected by

visual feedback. A further, albeit unlikely, possibility exists that visual feedback is not

useful during the movement with which it is associated, but rather that information, for

example of terminal location, is beneficial for subsequent trials, in terms of what, for

Schmidt (1975) would constitute an updating of the "recall memory" or motor schema. In

experiment 4 of the Zelaznik et al (1983) series, information regarding the feedback status

of the forthcoming trial was provided prior to each individual movement and feedback 5 7

Page 72: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

conditions were alternated over trials. The results strongly favoured the explanation which

posits that visual information is utilized during individual vision trials. Beaubaton and Hay

(1986) have given further consideration to the balance between "corrected ongoing

responses" and "amended delayed responses", and the manner in which this may vary as a

function of both movement time and the nature of the feedback which is available.

More recently, Young (1987) has attempted, to both c o b the potency of the

effects elucidated by Zelaznik et al. (1983), and to examine whether increasing the salience

of monitoring the target position, in terms of satisfactory task completion, alters the relative

importance of hand and target information (c.f., Carlton, 198 lb). In addition to the

manipulation of ambient and target related visual information, the target was potentionally

subject to perturbations coincident with movement initiation. Movement times in two

conditions approximated to 165 and 330 ms respectively. In both instances, movement

endpoints were biased in the direction of target motion, providing further evidence that

visual information may be utilized more rapidly than assumed by Keele and Posner (1968).

This biasing persisted when either target information or ambient lighting was removed 50

ms after the initiation of movement, suggesting that visual information pertaining to target

motion can be disseminated during the first 50 ms of movement. Young (1987) proposes a

possible feedforward role for this information, clearly vision of the responding hand and

target in the first 50 ms of motion could not be used as a substrate on which to evaluate

changes of relative position, and thus feedback based corrections, at least in central vision

(unless the movements were particularly slow, and both target and hand were in the central

field of vision, which does not appear to be the ase). 1 There was a failure to replicate the findings of Zelaznik et al. (1983) in that, for

stationary targets, no differences in spatial accuracy existed between ambient lighting

present or target continuously present, and ambient lighting removed and target illumination

removed. However, it should be noted that there was in all instances a lag of 50 ms

between movement initiation and the removal of visual information, therefore, in this task

at least, the initial information regarding hand, and target position and motion, was

sufficient upon which to base the accurate completion of the movement.

Accurate in this instance merely implies that the level of inaccuracy between

conditions was equivalent as assessed by the behavioural indices used by Young (1987).

This does not bear entirely upon the issue that the activity of the nervous system may be

differentially affected by the relative variations in the optic array or that in a functional sense

the satisfactory completion of a goal directed act may be contingent upon the availability of

visual information in a fashion which evades detection by conventional behavioural or

indeed kinematic measures (c.f., Pelisson et al., 1986). 5 8

Page 73: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

As previously noted, and as remarked by Zelaznik et al. (1983, p. 218) "estimation

of visual feedback processing time is not just an empirical adventure", clearly it has a

bearing on issues pertaining to the centralist versus peripheralist debate, and in particular

with respect to the concept of the "motor program". More importantly, in this context, it is

central to consideration of the manner in which, at least visual, feedback is involved in

modifying the outcomes of ongoing movement.

It has for some time been assumed that the alterations made during the course of a

reaching movement arise only during the latter phases of the movement, during which

portion, it is assumed, the position of the seen hand may be compared with target position

(e.g., Keele & Posner, 1968; Beggs & Howarth, 1972; Crossman & Goodeve, 1963).

There has, however, been continuing debate as to the way in which this latter phase,

supposedly mggered when with the eye fixating the target the retinal image of the hand

approaches the fovea, was subject to alteration as a result of required or desired movement

precision. Crossman and Goodeve (1963) and Keele (1968) suggested that aiming

movements consisted of an initial propulsive or "ballistic" movement which, it was

assumed, consists of some error and a second phase comprising as many error corrections

as were necessary to achieve target contact. It was also assumed that these corrections were

of a constant duration, therefore as greater precision was required or movement amplitude

increased, it was held that overall movement time would increase as a consequence of a

greater number of error corrections. The problems inherent should by now be apparent, no movement or movement segment can be truly "ballistic" if it is held to p e e d in the

absence of concurrent "feedback" of any nature, it is always likely that some facility exists

for "correction" on the basis of proprioception and/or efference copy (Goodale, 1987). If a

weaker definition of ballistic is adopted whereby it is to apply only to movements which

proceed in the absence of visual feedback, provision may be made only, at the present time,

for movements of rather less than 100 rns A second problem accompanies any suggestion that the initial propulsive phase

contains error. One ought to enquire, error with respect to what? For the organism itself,

errors can only be assessed with respect to the achievement of task goals, to suggest that

one may have an error in a movement subcomponent, regardless of the movement

outcome, by implication presupposes the existence of some recipe of action, which, if not

specifying the entire course of the action ought then to specify the "ideal" situation at that

point. As Greene (1972) forcibly argues, it is highly unlikely that such recipes exist. As if

to relieve investigators of the burden of addressing either of these issues, the studies

examining rapid aimed movements have rarely demonstrated the presence of more than one

corrective response (Carlton, 1979). In response, Keele (1981) has embraced the Howarth, 5 9

Page 74: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Beggs and Bowden (197 1) model, wherein, as accuracy demands are increased, movement

time is increased such that a greater proportion of the movement amplitude is covered and

the hand is brought closer to the target before corrective adjustments are made( see also

section ). In contrast, Carlton (1979) observed that modifications of required precision had

little effect upon the initial impulse, rather the increased time necessary to complete "more

difficult" tasks appeared to be due to an increase in the decelerative portion of the

movement. These observations are fundamentally in agreement with indications obtained

by Annett, Golby and Kay as long ago as 1958.

7.2 THE MULTIDIMENSIONAL CONTRIBUTION OF VISION

How arbitrary is this segmentation of aimed movements? In the following sections,

a line of reasoning will be developed which in its essence owes a great deal to the French

INSERM group of experimental neurophysiologists. The resulting perspective may

potentially reconcile apparently conflicting indications of both early and late accommodation

to increased accuracy demands. It will be suggested, following Pelisson et al. (1986) that

updated information relating to target position is conventionally utilized throughout the

entire duration of the movement. Further, aimed movements may be continuously regulated

with respect to variations in the optic array, whether these be due to target motion, target

size (associatively required precision) or the presence or absence of target, hand or ambient

illumination, and in conjunction with information from non-visual sources. This vista will

then be used as a basis on which to conduct further examination of potential asymmetries in

visually guided reaching.

Although, in most cases, the goal of a movement is defined by visual parameters,

visual information constitutes merely one input contiguous with an ongoing attempt to

match the final position of the limb to the position of a target which, although initially

defined in terms of visual space, must be referenced to egocentred, multimodality,

extrapersonal space. In what might be taken as a pragmatic approach to establishing the

invariances associated with limb movements, motor-physiologists have not only typically

restricted consideration to one degree of freedom movements (Bizzi & Morasso, 1982),

neglecting the three dimensional movement through space which characterizes our daily

lives, but have "ignored the manner in which visual information contributes to the

spatiotemporal topology of goal directed movements" (Fisk & Goodale, 1985, p. 160). On

the other extreme, and as has already been extensively catalogued, a large body of

researchers have attached paramount importance to the role of vision and in particular to

visual feedback as an error signal, and have rarely entertained consideration of non-visual

factors let alone the import of these factors to an organism which must deal with a single, 6 0

Page 75: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

unitary external world. The role of vision is itself multidimensional, and it is this absence

of a single function for vision (such as error correction) which has provided the clearest

indication of the necessary role of non-visual factors and thus of the nature of the "system"

as a whole.

Prablanc, Eschallier, Komallis and Jeannerod (1979) demonstrated that the

relationship between movement time and the "index of difficulty" (the ratio of movement

amplitude and target size as described by Fitt's Law, see Section 8.1) characteristic of

visually aimed movements, is preserved when the movement is conducted without vision

of the reaching hand It seems therefore that the accuracy of the movement (as defined by

the index of difficulty) is governed not only by visual feedback of the hand but also by

proprioceptive information and conceivably "efference copy" associated with the motor

output. Whilst one may find it necessary to dispute that "such information must have been

compared to some internal representation of the target" (Prablanc, Pelisson & Goodale,

1986, p. 294), on the basis that it is not necessary to posit a "mental" representation, nor as

a result that a comparison takes place, it is clearly the case that visual information regarding

the position of the target has an action guiding function for movements which are themselves not seen.

With a view to extending these findings, Prablanc et al. (1986) manipulated the

availability of target information for movements which were again made in the absence of

visual feedback. Four target conditions were utilized; in the fist condition the target LED was extinguished upon movement initiation, in condition 2 the target was removed 120 ms

after completion of the initial eye saccade toward the target, this enabled the subject to make

a corrective saccade aligning the eye with target position before the target disappeared, the

third condition permitted vision of the target throughout the movement, whilst in the final

manipulation, which may be usefully contrasted with condition 2, subjects were directed to

complete their eye movement and thus obtain accurate foveal information regarding the

target before initiating a movement which caused the target to be removed Movement

accuracy, in terms of constant error, was found to increase from conditions 1 to 3, accuracy for condition 4 was between that for conditions 2 and 3. Generally then, there

was an improvement which paralleled the duration of target display. In discussing these

trends, Prablanc et al. (1986) reason thusly, " 'open loop' movements (open loop with

respect to visual feedback about the relative positions of the target and the moving limb) are

far from being uncorrected or ballistic. Indeed, the prime effect of target duration on

pointing accuracy suggests that visual information about target location is somehow used to

control the movement during its execution." (p. 300).

Page 76: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

It also appears that the particular nature of that visual information assumes some

significance, accuracy for condition 4 in which foveal information was available was

superior to condition 1 in which it was not, yet accuracy for condition 3 for which foveal

information was present throughout the greater part of the movement was superior to

condition 4. The advantage for condition 3 over condition 2 appears to indicate that the

extra-retinal signal regarding eye position is, in this instance, not a sufficient basis on

which to guide the reaching movement (c.f., Mather & Fisk, 1985). In concluding,

Prablanc et al. (1986) speculate that ongoing corrections conducted on the basis of, visual

target information, and that which is motion related but from non-visual sources requiring

very little time, are characteristic features of normal reaching movements. The results of a

closely related study (Pelisson et al., 1986) provide converging evidence that this may

indeed be the case.

Under consideration were the nature of aiming movements, made without vision of

the responding limb, to targets which had been perturbed during eye saccades. It is a

property of the oculomotor system that initial saccades tend to undershoot the target, this

has some heuristic value, if more accurate information about target position is subsequently

made available, it is better to have underestimated than overestimated, particularly with

respect to the amplitude of a required movement (Prablanc et al., 1986). The initial saccade

is rapidly followed by a second which brings the target into foveal vision. Generally, if a

target if a target is displaced by a few degrees of visual angle or about 10% of saccade

amplitude during the first saccade, the movement of the stimulus is not available to

conscious perception. It appears that the perceptual system "assumes" that the discrepancy

has arisen from an inaccurate first saccade. Pelisson et al. (1986) induced target

displacements on randomly determined trials, and in a manner consistent with previous

investigations (e.g., Mackay, 1970; Brooks & Fuchs, 1975; Matin, 1982), subjects were

unable to identify the trials on which perturbations occurred. It is a further characteristic of

responses made to targets presented in the visual periphery that EMG onset in the brachial

and ocular musculature is virtually simultaneous (Biguer, Jeannerod & Prablanc, 1982).

Although initiated together, the initial saccadic eye movement is the first completed as the

eye has smaller inertial forces to overcome. Therefore, it is the case that displacements of

the visual target during or after the initial saccade necessarily occur after the response

movement has been initiated. The most significant results obtained by Pelisson et al. were

that there were no differences in localization errors between trials on which the target had

been displaced and those on which the target had remained stationary.

As with the experiment conducted by Prablanc et al. (1986), it appears the case that

modifications of the response movement could be accomplished in the absence of visual 6 2

Page 77: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

information relating the relative positions of the limb and the target. The results, in addition

appear to rest comfortably with those obtained by Megaw (1974), subjects were able to

successfully modify ongoing movements when targets were displaced by a few degrees

within 100 ms of movement initiation.

In the Pelisson et al. (1986) study, the responses were subjected to a kinematic

analysis, however. Most significantly, the modifications of the reaching movements

manifest in the accuracy measures were not revealed as inflection points in the velocity

profile. Acknowledging that it is in practice impossible to distinguish between early discrete

mmcations which have been filtered by the inertial properties of the limb, and

"continuous control", the authors argue in favour of a " 'pseudo-continuous' corrective

mechanism acting upon the hand trajectory: the new target position information is not only

used near the end of the movement but earlier as well" (p. 3 10).

It is also of particular interest to note that the mechanisms responsible for the

regulation of the motor response were somewhat more acuitous than the perceptual

equivalents, individuals were never aware of the change in target position. Converging

evidence that there exists a plurality of visuomotor mechanisms is provided by patients

suffering hernianopia, and having lost vision for one half of the visual field usually

following a unilateral lesion within the visual cortex. These individuals are generally never

consciously aware of visual stimuli presented to the hemifield opposite to the lesion or on

occasions to that side of extrapersonal space. The presence of some tangible sub-cortical

visual functions has been revealed through having subjects guess as to the locations of

visual stimuli (Jeannerod & Biguer, 1982). When target stimuli are presented in a

purportedly "blind" area, hand pointing (Weiskrantz, Warrington, Sanders & Marshall,

1974; Perenin & Jeannerod, 1975) and eye movements (Poeppel, Held & Frost, 1973)

revealed that individuals were able to locate that of which they were not consciously aware.

The same phenomenon has been observed by Perenin and Jeannerod (1978), patients made

movements toward targets presented in the blind hemifield which, in terms of accuracy,

were equivalent to those made by controls.

7.3 THE CONTRIBUTIONS OF CENTRAL AND PERIPHERAL VISION

Whilst all aimed reaching movements are in some sense goal directed, ultimately

each movement will be directed towards some particular aspect of the visual world,

whether this is an object to be lifted and placed or simply a spot which must be contacted.

The highly function specific termination to many reaching movements has lead a number of

theorists, most notably Trevarthen (1968) and Schneider (1969) to propose that there exist

at least two segregated visuomotor pathways, subserving "shape" and "spatial location", 6 3

Page 78: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

what in Paillard's (1971) expressions are "l'espace des lieux" and "l'espace des formes".

For the present purposes, consideration of modifications of the reach which are sensitive to

the intrinsic properties of the target object, such as weight or shape, (c.f., Marteniuk,

Leavitt & MacKenzie, 1987) will be simplified to consider merely those visual mechanisms

responsible for reasonably precise guidance of a single finger or hand held stylus to a

"punctiform" of point target. 'The "classical" perspective (e.g., Keele & Posner, 1968), as

has been extensively outlined, holds that most reaching movements are too rapid to permit

utilization of visual feedback in anything but the final portion of the deceleration phase.

Whilst visual feedback may certainly be mediated more rapidly than initially presumed,

there is clearly also some initial portion of the movement during which visual feedback

cannot be used as a basis for discrete modifications. As revealed however, the nature of the

visual information available during this period has profound effects upon the movement

outcome. The high velocity and segmental pattern of muscle activation during this initial,

otherwise termed ballistic, portion of the movement has extensively been viewed as a

reflection of preprogrammed unmodifiable motor commands (c.f., Glencross, 1977). Yet it

does appear that the initial phases of "error correction" are based upon "central monitoring

of the commands for movement", and may take the form of suppression of muscular

activity prior to overt manifestations of motion in the movement which is ostensibly being

corrected (Cooke & Diggles, 1984).

What is seemingly an independence of visual reafference and a clearly modifiable

progression may potentially be reconciled if one accepts the tenet of Jeannerod and Biguer

(1982) that at least some portion of the visual information available during this portion of

the movement enters the "space channel". It is suggested that not only are "space" and

"object" channels subserved by specific areas of the brain, but also that the motor output

with which these channels are intimately associated is similarly specialized and distinct.

Thus, 'space' channels have a completely different function: to match the final position of the moving limb with the position of the target within extrapersonal space. For this purpose, central visual processing can be limited to the computation of a set of spatial coordinates establishing the location of the object with respect to the body. This requires that the central 'map' used to relate each point of the visual field to the visual system encode body-centred coordinates, rather than retinal coordinates only. Both the position of the eye with respect to the head and the position of the head with respect to the body must be taken into account in determining the direction of the arm movement. In addition,eye, head, and body movements may themselves become part of the act of reaching when it is directed at an object within a peripheral part of the visual field (Jeannerod & Biguer, 1982, p. 388).

Page 79: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

This latent computational approach does not seem to be the most assuring basis on

which to proceed, as it stresses the motor or action guiding function of internal

representations rather than of perception per se, nonetheless it does contain elements which

are germane. Certainly, it does appear that central and peripheral vision do provide some

what distinct contributions to the regulation of aimed hand movements. Paillard (1982) has

ex~ressed his conviction that. I

to some extek peripheral vision can be regard ed... in charge of the transport of the hand form its initial position toward the target with the computing of the appropriate trajectory, and central vision might be considered as providing ... the cues necessary to achieve the precise and smooth landing of the hand on the target (p. 367).

One may perhaps dismiss the suggestion that one "appropriate trajectory" is subject to

computation, clearly there are an infinite number of movement trajectories which may lead

to the satisfactory accomplishment of the task goal, it is not even a requirement that they all

have the same end point, as in this conceptualization, "precision" and "smooth landing"

itself variable is superimposed upon the movement trajectory. Neither is it apparent that any

"computation" as such need occur. However, there is evidence that central and peripheral

vision do assume distinctive roles within the regulation of aimed movements.

Paillard's interpretation has inherent, the assumption that the vision of the limb,

which has been shown to be useful when provided only during the initial phases of the

movement, is processed only in the peripheral visual field Conti and Beaubaton (1976)

manipulated conditions such that visual feedback could be provided through various

portions of the movement, such as the first third or the second half of the trajectory. The

salient findings were indeed that visual feedback, even when provided during the initial

phases of a movement leads to an improvement in performance. This is assumed to be

vision of the trajectory which should be distinguished from vision of the target, for

example with respect to target motion. There is also converging evidence which indicates

that adaption to prismatic disturbance of vision may be subserved by distinct mechanisms

for the restoration of order to peripheral and central vision respectively (Brouchon-Viton &

Jordon, 1978). In completing his (1982) synopsis, Paillard reasons that movement cues,

and in particular "self moving stimuli" or vision of ones own body segments, are

predominantly processed in the periphery and are intimately associated with motion relative

to a visual axis established by foveal grasp of the target (c.f., Paillard, 1980). It is this

relativity to both the visual axis defining visual space and to the motion of the body, which

as has been stressed, must be with reference to egocentric and non-modality specific space,

which suggests that peripheral vision is allied to the regulation of the movement trajectory,

at least in its initial stages.

Page 80: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 8

ASYMMETRIES OF RAPID AIMED MOVEMENTS

8.1 THE ROLE OF FEEDBACK PROCESSING

One might enquire how the functional characteristics of the visual guidance

mechanisms may also be related to asymmetries in the regulation of movement. The

observation that a reaching movement is perturbed when concurrent vision from the

peripheral field is removed was made by Trevarthen as long ago as 1974. Significantly, his

results indicated that : peripheral vision of the movement of either arm is governed, at least in the commissurotomy subject, more by the right hemisphere, while coincidence of eye and hand in fmation of the point target is governed more from the left hemisphere (p. 253).

As noted, one traditional perspective emphasizes that manual symmetries are a function of

the differential efficiencies with which visual feedback is processed. In particular, the

preferred hand is ostensibly associated with a neural substrate which may more effectively

use this visual feedback to effect error corrections apparently required for accurate

responses (e.g., Doane & Todor, 1978; Flowers, 1975; Todor & Doane, 1978). With

respect to this approach, it has been customary to link the performance of each hand with

the assumed processing characteristics of the contralateral hemisphere. In terms of the

dichotomy presently favoured by theorists of motor control (e.g., Todor & Doane, 1978),

the left hemisphere is allegedly superior for the processing of information in a sequential

manner, whilst the right hemisphere can deal more effectively with the parallel processing

of information (c.f., Cohen, 1973).

Although this dichotomy of function has a certain intuitive appeal, the left

hemisphere and thus the right hand will demonstrate a superiority in dealing with the

sequential input of sensory feedback which is supposedly characteristic of certain aimed

movements, the situation is a good deal more complex than this characterization might

suggest. As outlined in section 3.2, the notion of dichotomous hemispheric specialization is

some way from being accurate or indeed pragmatic and, as revealed in the preceding

section, the role of visual information in the regulation of movement is itself highly

complex and very much dependent upon task constraints.

Consideration will be given to a series of experiments instigated initially by Flowers

(1975), all of which have in common highly constraining initial assumptions, both implicit

and explicit, as to the nature of both the integration of visual information and the

asymmetrical organization of the nervous system. These studies are worthy of

Page 81: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

reexamination, as it is through consideration of their specific task parameters that the results

of these studies may be accommodated within the body of literature already discussed.

Flowers (1975) hypothesized that there existed during aimed movements a "corrective

mode of control". It was further held that the use of the Fitts reciprocal tapping task

permitted the appropriate manipulation of the required level of control and that, if between

hand were observed to vary as a function of these demands, it could be concluded that: "the

essential dexterity difference between the preferred and non-preferred hands is in the

sensory or feedback control of movements rather than in motor function per se" (p. 39).

It should be noted that the "Fitts Tapping Task" differs si@icantly from those considered

in section 6.2. It is a central tenet of the Fitts task that the requirement for the use of

feedback may be manipulated through the modification of very specific task parameters

(c.f., Peters, 1980). In Fitts' "classic" exposition, it was postulated that the number of

possible alternatives which could be made "correctly" for any given response determines

what is regarded as the level of "precision". Using a small target, relatively few responses

would suffice as correct, whereas with a larger target, a number of responses drawn from a set of similar movements would be scored as correct. Similarly, as the amplitude between

successive targets is manipulated, the precision covaries. The two measures were combined

in producing an index of difficulty (ID) such that:

(1) Id = log2 2 x am~litude of movement (bits)

width of the target

Within the framework assembled within an information processing perspective,

Fitts (1954) suggested that the speed with which movements were made was governed by

the capacity limits of an individual's motor system and by the "information" required to

make any one movement. The above relationship can alternatively be expressed in terms of

movement time, as follows:

where A is the amplitude of the movement, W is target width, and the constants a

and b are obtained empirically.

There has generally followed, the implicit assumption that for cases in which the

amplitude between, and size of targets is futed, the resultant speed of movement may be

taken as some measure of the capacity of the "hand system" to make the response (e.g.,

Flowers, 1975). It was proposed that at low ID values, individuals are responding with 6 7

Page 82: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

ballistic movements, by which the intended meaning is presumably unmediated by sensory

feedback, whilst for more "difficult" combinations it was necessary for subjects to adopt

the use of some form of corrective procedure.

The problems inherent in a distinction between ballistic and non-ballistic (in

circumstances in which normal vision is maintained) are overlooked by (Flowers, 1975),

for whom the data decides. Statistically significant differences between the hands, in terms

of movement duration and proportion of target misses, were observed at ID values 4 and

above, for subjects classified as strongly lateralized. Flowers (1975) was led to conclude

that the preferred hand advantage for "non-ballistic" movements was due to the "lower rate

of information transmission" for the non-preferred hand, which would presumably then be

revealed on any task permitting rapid processing of concurrent sensory feedback and thus

all movements. That these experiments failed to elicit indications of asymmetries in

movements having ID values smaller than 4, and for simple tapping (which is clearly in

itself in conflict with a considerable body of research) is perhaps indicative of the relative

insensitivity of the response measures employed. Indeed, it is notable that Flowers (1975)

concludes that the data are in agreement with the findings of Woodworth (1899) in that "left

hand movements become ballistic if they take 750 ms or less, while right hand ones only

become ballistic at 400 ms" (p. 50). In a partial replication of the Flowers study, Todor and

Doane (1978) failed to obtain right hand superiority in conditions apparently requiring

greater feedback control. Performance was assessed in terms of hits per ten second

interval, a measure which is similarly impoverished, providing few indications of the

manner in which the hands differ.

8.2 THREERECENTSTUDIES

Perhaps the most adequate examination of the proposal that asymmetries are due to

differential efficiency of processing feedback information was that conducted by Todor and

Cisneros (1985). Employed were single aiming movements, again within a Fitts-type

paradigm, for which it was possible to manipulate required precision. The use of an

accelerometer and subsequent identification of acceleration changes led the authors to

partition the movement into four specific phases. These were time to peak positive

acceleration (TI), time h m T1 to acceleration reversal ( 7 3 , time from T2 to peak deceleration (T3, and time h m T3 to target contact (T4). Todor and Cisneros suggest that

aiming movements of this nature, with durations greater than 400 ms may be partitioned

into further distinct stages. Uncontroversially these are a distance covering phase, and a

"homing in" or "error correction" phase corresponding to T4.

Page 83: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

The results appear to indicate that the largest hand differences were exhibited in the

latter phase, these in turn increased in magnitude with the demand for precision. This, the

authors believe, demonstrates an enhanced ability for the preferred hand in executing error

corrections. It should be noted however that there was a right hand advantage for the final

portion of the distance covering phase. This portion, T3, was, presumably, what the

authors would have regarded as a programmed aspect of the movement. Thus it appears

that the asymmetry is not entirely associated with differing facilities for error correction in

the T4 stage, since the preferred hand exhibits some form of advantage prior to this point.

It is perhaps unfortunate that there was no means of assessing the variability of

movement in the initial phases TI, 7'2 and T3. Todor and Cisneros (1985) performed more

detailed analysis of the movements themselves which indicated that when greater accuracy

was required, the hand was brought closer to the target before correction was made. This

was generally correlated with a higher initial velocity maintained for a longer period of

time. Whilst these observations would initially appear to conflict with the predictions based

on the Schmidt, Zelaznlk, Hawkins, Frank and Quim (1979) model of output variability,

there is no reason to suppose that the pattern does not reflect an initial superiority of the

preferred hand. The evidence from the T3 stage appears to suggest such a superiority, and

indeed it seems counterintuitive to suggest that the advantage apparently enjoyed by the

right hand for making corrective movements arises as a result of a less satisfactory initial

movement. It does rather appear that the adoption of a two stage characterization serves to

obscure rather than to illuminate.

Turning to even more recent evidence, Roy and Elliott (1986) employed a pointing

task for which a range of movement times were obtained. Dependent measures were a 'self

paced' movement time measure 'movement time', and 'radial error', consisting of

amplitude error (i.e., error in the direction of the target) and directional error (i.e., error

perpendicular to amplitude error). Both directional and amplitude error can themselves be

expressed in terms of constant and variable error.

The rationale appears to have been that with increased movement speed, and thus

reduced movement time, there would be less visual information available upon which to

base corrections. There is an obvious problem with this, in that, shorter movement times

are likely to be associated with higher initial velocities resulting from greater force

production. This may in itself result in a decremental effect on performance which is

expressed asymmetrically, for example as a consequence of the relative inability of the

non-preferred hand to achieve precision of force modulation. This has, on occasions, been

assumed to be an aspect of programming. Roy and Elliott predicted that examination of the

speed-accuracy trade-off function should reveal a steeper slope for the left hand as a result 6 9

Page 84: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

of its reduced efficiency of processing visual information. However, any such difference in

the slope of the function could equally well have been said to reflect the increasing effects

of force variability as movement speed increases.

A second level of manipulation was employed whereby ambient lighting was

removed upon presentation of the stimulus. This was assumed and indeed appears to be a

more direct means of manipulating the amount of visual information which is available

during movement. The authors again predict that removal of visual information should

affect right hand performance to a greater degree than left hand performance which, in line

with Todor and Dome (1978), they suppose is dependent on a preprogrammed mode of

control.

In broader terms, it seems implausible to suggest that the movements of each hand

are conducted on bases which are qualitatively different. This is particularly so in the

context of conventional movements in normals for whom "information" is available to both

hemispheres on what is essentially a continual basis. Certainly, it may be the case that one

hemisphere will demonstrate relative benefit for the processing of material of a given

nature, but this will in itself be a matter of degree. It does not seem to be the case that the

movements of the left hand should depend only upon a preprogrammed mode of control.

As noted in section 3.1, it is widely held that hemispheric asymmetries might best be

considered a continuum rather than as some bipolar system. In contrast to the view

forwarded by Roy and Elliott (1986), a more comprehensive model would lead to an

alternative way of evaluating these effects, specifically, that the removal of visual feedback

would reduce the relative level of enhancement for the preferred hand. Though it must also

be assumed that in many circumstances, for example those for which the necessity of

dealing with complex spatial relationships does not exist, the right hand will already exhibit

a "baseline" superiority, regardless of visual feedback processing demands, due to what

has previously been regarded as a presumed greater precision of force modulation.

The results obtained by Roy and Elliott (1986), in terms of radial error, c o n f m

expectations for this task that the right hand was more accurate than the left, that accuracy

increased from shortest to longest movement times and that performances when ambient

lighting was present were superior to those when it was removed. As movement speed

increased, there was a relatively greater decrement in accuracy for the non-preferred hand.

In terms of the speed accuracy function, the left hand had a "steeper negative slope".

Significantly , however, the difference in slope between the two hands did not vary

between illumination conditions, indicating that the differences were perhaps not due to

variations in the efficiency with which the visual information was processed. There was, as

noted, an effect of illumination per se, this appears to suggest the almost equal expression 7 0

Page 85: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

of this effect over both hands. This is unexpected, though it is possible, as Roy and Elliott

(1986) themselves indicate, that the dependent measure radial error, which is a composite

of both constant error and variable error, was not entirely appropriate for these purposes. It

is conceivable that the composite measure obscured a right-hand advantage in terms of

variable error for movement execution.

With a view to examining the issue further, Roy and Elliott (1986) conducted a

further series of experiments in which subjects were required to conduct movements in less

than 200 ms This was assumed to preclude the possibility of visual corrections during

movements, though as considered in the previous chapter, visual feedback "loops" may

operate over latencies much shurter than 200 ms. Dependent measures were, in this series,

reaction time, movement time and radial error. With respect to the reaction times obtained,

it is notable that a feedback by hand interaction was obtained. Subjects required less time to

program left hand movements in the illuminated condition than in the other three

permutations. This is interesting and may reflect the enhanced ability of the right

hemisphere to integrate and assimilate the spatial relationships associated with the task, a

difference which would presumably not be evidenced for the non-illuminated condition.

Movement time analysis indicated a main effect for hand and a hand by feedback

interaction. This effect was also evident in the initial experiment but failed to reach

statistical sipficance. Specifically, the right hand advantage in movement time was

greatest in the illuminated condition. This would appear very much in line with suggestions

that the left hemisphere exerts its superiority for the processing of feedback information at

this stage.

In terms of radial error, a right hand advantage was again observed, though there

was an absence of any interactions. Again the compound nature of this measure may have

obscured a number of effects. Of course, the right hand advantage on an overall measure of

pointing accuracy is not unanticipated. Roy and Elliott (1986) suppose that the right hand

advantage observed in this instance could not have been due to differential feedback

processing as there was no significant difference in pointing accuracy between the two

illumination conditions. The difference between illumination conditions, although not

statistically significant, was in the direction anticipated.

In view of the hand by illumination interaction for movement time, one would have

to question the use of the compound radial error as the final arbiter of this issue. In

addition, it is possible that some of the between hand differences could be accounted for in

terms of non-visual feedback processing, once more assumed to proceed in latencies of less

than 200 ms Rather than excluding processes mediated by feedback, as the authors

suggest, the evidence appears to indicate that both types of processes may be occurring. 7 1

Page 86: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Although in this study it was not possible to examine the decomposed error scores, the data

are not incompatible with a global model which emphasizes the plasticity of the contribution

made by visual information, and as such considers as a primary determinant of the

asymmetrical manifestation of this contribution, the task constraints associated with various

forms of goal directed action.

In a follow up of the 1986 study, Roy and Elliott gave further consideration to the

relative contributions of, inherent differences in the variability of force output, and possible

variations in the utilization of visual feedback Roy and Elliott (in press) viewed anchoring

of movement time for movements of various amplitudes as a way of varying the force

required to complete the movement and thus a means of examining between hand

differences in force variability.

As noted previously, the use of target movement times is probably more

controversial than the more usual yet questionable use of target latency bandwidths. Setting

a task goal which is incompatible with other task constraints may well induce the use of

strategies resulting in variation in the type of movement made in each case. Thus, different

movements are being made rather than what is essentially the same movement differing

only in the amount of force initially produced. Obviously behavioural indices such as error

scores can provide no assurance that the movements are indeed equivalent as these

constitute the dependent measures of primary interest. In the absence of ratification of the

equivalence of response profiles through the use of, potentially, kinematic analyses, one

cannot distinguish between variations in accuracy which arise as a consequence of

variegated initial production of force or from movements which are, in essence dissimilar.

Roy and Elliott considered that "long" and "short" movements made from two

home positions, 25 and 35 cm from a single target, constituted an adequate manipulation of

required force, when subjects had been "trained" to complete the movements within time

ranges of 150 to 249 ms, 250 to 349 ms and 350 to 449 ms As the authors themselves

point out, the use of a single target and a single starting location in the 1986 study

represents a considerable limitation. It is indeed likely that this lead to "less reliance on

visual information" (Roy & Elliott, in press). Nonetheless, it hardly seems that the use of

two spatially distinct starting locations is a great improvement. There are some indications

that when sets of a very few targets are employed, superimposed manipulations such as the

removal of visual feedback have substantially reduced effects (c.f., Guiard, Diaz &

Beaubaton, 1983). The use of a single target position is in itself problematic, the concept of

"equifinality", that a movement pattern can be reached "reproducibly" from a variety of

initial conditions, is a pivotal assumption in contemporary approaches to the study of motor

control (Kay, Kelso, Saltzman & Schoner, 1987). If this principle is upheld, one must

Page 87: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

consequently question the legitimacy of second order manipulations such as that of

illumination.

In the study itself, three conditions relating to visual feedback were utilized, ambient

lighting removed upon movement initiation, ambient lighting removed 10 sec. prior to

movement initiation, and ambient lighting present throughout the movement. Of import

with regard to the suggestion that the hands differ in terms of the variability of force output

is the measure of variable error. The results in this instance indicated that there was no hand

by movement distance interaction for this measure. Thus, if one assumes that movement

distance was indeed an indicator of required force, one must similarly conclude that there

was no difference in the variability of force production between the hands. Perhaps it is in

this regard that the significance of using a single target with two starting positions should

be viewed, rather than with respect to the use of visual information. That is, the use of a

single target location may have served to depress what were, potentially, between hand

differences in variability.

Examination of constant error perpendicular to the direction of movement indicated

that a three way interaction of hand, vision and distance had occurred Although it seems

that the trend was for right hand movements to be biased to the left, and for left hand

movements to be biased to the right, when ambient lighting was removed, no indication of

the trends in the absolute variation in this error was provided, thus it is difficult to establish

whether the "performance" of each hand was differentially affected in a summary fashion.

Variable error perpendicular to the direction of motion was affected by visual condition in a

manner similar to variable error in the direction of motion.

It is interesting to note that although robust variations in variable error were

obtained as a result of manipulating visual information, there was no concomitant effect

upon movement time. This is unusual. Although the view that discrete corrections based

upon visual information take a constant amount of time, has all but dissolved (see section

7. I), it has generally been observed that the removal of visual information, when this is

assumed to be acting as some substrate for the modification of ongoing movement, is

accompanied by an decrease in movement time.This was not the case in the Roy and Elliott

(in press) study.

The authors themselves suggest that the consequences of the 10 sec. delay interval,

in terms of accuracy, may have been due to the deterioration of a "visual representation".

They also perhaps fail to appreciate that this could also have been the case in the condition

in which vision was removed upon movement initiation. When a 10 sec. delay was

present, visual information regarding the target was absent for 10 seconds plus the duration

of the movement. When movement initiation triggered the removal of ambient lighting, 7 3

Page 88: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

visual information of the target was absent for the duration of the movement as the target

was not illuminated independently. Thus the effects of the visual condition could have been

due to a bilateral deterioration of the information relating to target position in extrapersonal

space over the interval between the last instant at which target information was available

and movement completion, rather than the removal of the information upon which

corrections are made, which is that process which may proceed asymmetrically.

The importance of considering the delays between the instants at which information

upon which "successful" movement, in part, depends is last available, and the execution of

the movement itself, whether this interval be "filled" or "unfilled", has been highlighted by

Carson (1987b). It does appear that for the movements considered by Roy and Elliott (in

press), completion did not only rely upon the presence of visual information during

execution, particularly when a single target position was employed and movements were

essentially two-dimensional, that is the plane on which the target was located was the plane

on which the movement started. As Roy and Elliott (in press) recount, the differences in

accuracy between the traditional "lights-on" and "lights-off' conditions were small even for

the longer movement times, and diminished as movement times decreased. In line with the

suggestion outlined above, for shorter movement times, the difference in the duration for

which target information was available between movement initiation and completion

represented a smaller difference between visual conditions than for longer movement times.

The seemingly striking effects of the visual information manipulation, most evident for the

10 sec. delay condition could, in all cases, be viewed as being due to a deterioration of

information relating to target position over time. Therefore the experiment does not

constitute an adequate test of the hypothesis that manual asymmetries are not due to

dissimilarities in output variability, or rather that they are due to the ability of the "right

hand system" to more accurately modulate force (Roy & Elliott, in press).

In a second reported experiment, ostensibly conducted as a means of further

examining this hypothesis, Roy and Elliott had subjects make aimed movements as rapidly

as possible, assuming that this would increase any differences which existed between the

hands in terms of force variability. This experiment also differed in that four additional

starting positions were used, which allowed movements with either hand to be initiated

from either the right or the left of the midline. It is clear however, that as a single target

location was again used for all conditions, it was merely the starting position which was

varied. Therefore, the problems associated with the use of planar movements to a single

target location were not alleviated. Roy and Elliott obtained no indications of a hand by

movement length interaction which, in their terms, would have provided evidence

pertaining to a force variability interpretation, though perhaps in this instance, examination 7 4

Page 89: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

of the variation by movement time (i.e. using post grouped movement times as an

independent variable) for a given movement length would have provided a more

appropriate test of this issue. In the absence of confirmatory kinematic profiles, one may

only assume that movements made over the same movement length are equivalent, however

it would seem reasonable to conclude that shorter movement times are concomitant with

greater initial production of force.

There was one notable deviation from the results obtained for experiment 1, in that

for constant error in the direction of movement, something of a hand by visual condition

was obtained. Both hands had a tendency to undershoot the target, which for the right hand

was equivalent across all visual conditions, and for the left hand similar for the vision and

no-vision conditions but greater to a statistically degree when there was a 10 sec.

premovement delay. Roy and Elliott (in press) feel this suggests that "when using the left

hand, subjects do not encode as clear a representation of target location, or they have less

access to this representation, or this representation decays more rapidly" (p. 19). If there is

indeed some visual representation of target position (itself unlikely) which is subject to

decay, the advantage of the right hand seems remarkable and unexpected in light of the

"known" superiority of the right hemisphere with respect to "spatial information". There

seems no reason to believe that the information pertaining to target position, initially

present, is not made available to each hemisphere to an equivalent degree. There can be

little dispute that the salient "information" is subject to decay over relatively short intervals,

however the decay is probably not modality specific (Carson, 1987b). If Roy and Elliott

have in mind some visual representation of an iconic nature (e.g., Sperling, 1960), it is

highly unlikely that such "storage" will persist for anythmg longer than a second after the

display has been terminated. If the decay was of a "representation" of a target in space, one

would assume that the deterioration would not be directionally specific, yet, no hand by

visual condition interaction was obtained for constant error perpendicular to the direction of motion. As the alteration in the magnitude of constant error was specific to the direction of

movement and was an extension of a bias already existing, one is led conclude that the

deterioration, in this instance, may be more closely associated with the motor output "side"

of a perceiving-acting continuum. Certainly, the suggestion that the left-hand / right-

hemisphere may less clearly "encode a representation of target location" is less than

convincing.

Page 90: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 9

THE SIGNIFICANCE OF SPATIALITY IN MOVEMENT

9.1 ARGUMENTS FOR ECOLOGICAL VALIDITY

One might do well to again consider that the superiority of the right hemisphere for

the manipulation of spatial relationships is virtually uncontested. Yet, remarkably little

consideration has been given to the implications of this with respect to motor activity. In the

final section of this review, the role of the right hemisphere in mediating purposeful, goal

directed action will be examined. The perspective to be adopted leads necessady to a

highly task orientated view of manual asymmetries and to an accompanying and continuing

rejection of the force variability / feedback processing dichotomy.

It is clear that the studies which have been conducted thus far have been noticeably

impoverished with regard to the complexity of the spatial relationships with which subjects

have had to deal. Often the movements have been two dimensional, in the sense that the

target and starting position lie in the same plane, any movement into the third dimension

may, in addition, be described in terms of a second plane perpendicular to the targetlstarting

position surface. The "tapping" movements typical of the Fitts' paradigm are perhaps the

clearest example of this type of restricted movement. In any attempt to provide a complete

account of manual asymmetries, and as Guiard et al. (1983, p. 11 1) point out, "one should

turn to more adequate tasks from the right hemisphere's viewpoint".

The "more adequate" task employed by Guiard et al. was a fast unimanual

movement to a visually presented target, located in what was assumed to be body centred

space, and for which vision of the movement itself was obscured. Guiard et al. were

probably misguided in considering their movements to be open loop and ballistic, clearly

this could not have been the case. The actual motion required was a form of reaching,

requiring motion in three dimensions, certainly it could be described as progression into

space. Their interpretation of results rested heavily upon the assumption (Granit, 1972;

Paillard & Brouchon, 1974) that constant error (i.e., averaged, signed, measurement

error) may be taken as indicative of the accuracy of "central programming", reaction time

then being considered an index of the speed of programming. Variable error (i.e., standard

deviation of scores about the constant error) is assumed to reflect the accuracy of motor

program execution, whilst movement time is the rapidity with which this is accomplished.

The results obtained by Guiard et al. (1983) indicated a superiority in terms of

constant error for movements made by the left hand and for targets presented to the left

hemi-field. The authors attribute these effects to "the superiority of the left hand in 7 6

Page 91: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

movement programming" (p. 113), in the absence of concurrent visual feedback. Although

not reaching statistical significance, the data obtained for movement time and variable error

indicate a trend toward a right hand advantage. In terms of the interpretation of error scores

favoured by Guiard et al., this suggests a superiority of the right hand for movement

execution.

Carson (1987a) was perhaps being naive in suggesting that these findings can most

easily be reconciled if one assumes that the superiority of the right hemisphere for

manipulating spatial relationships exerts its effects during "programming" of the

movement, whilst the assumed left hemisphere advantage for sequentially processing

feedback information becomes salient during movement execution. It is obviously not the

case that the influence of visual information can be parcelled out in this fashion. One might

ponder, however, whether that which is assumed to be a left hemisphere advantage for

processing feedback may be induced in circumstances in which sensory feedback is

diminished, in this case through the absence of vision of the responding limb. The trend

toward a right hand advantage which was evidenced for movement time and variable error

may have arisen as a result of the processing of information from non-visual sources. It has

elsewhere been noted (Paillard & Brouchon, 1974) that in the appropriate circumstances,

proprioceptive information arising from active positioning of a target finger might actually

lead to performance superior to that when visual information was provided.

9.2 CONVERGING EVIDENCE

Some further support for the view that manual asymmetries, in particular as an

expression of right hemisphere characteristics, may be seen across modalities is provided

by the work of Roy and MacKenzie (1978), in which examination was made of

asymmetries in the "blind" reproduction of spatial positioning movements. Using a thumb

positioning task, in what was termed the "kinesthetic modality", the authors were able to

elicit a marked left hand advantage in terms of constant error scores. Again this would seem

to emphasise that the right hemisphere advantage for localizing positions in space, exerts its

most obvious effects in terms of "processes" reflected in constant error scores. It should

also be noted, however, that a left hand advantage for variable error was also present. This

would initially appear to conflict with any model which predicts a right hand advantage,

expressed in terms of variable error, as a consequence of a left hemisphere role in the

concurrent processing of sensory feedback. However, the movements employed by Roy

and MacKenzie were "slow positioning" for which accuracy was the sole criterion. With no

requirement for speed, it is likely that the presumed superiority of the "right hand system",

for the processing of contiguous sensory feedback, was not exhibited to the same extent. 7 7

Page 92: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Examination of the effects of limiting the presentation of visual information to a

single visual field, and thus initially to one hemisphere, has been greatly enhanced through

the use of innovative procedures, such as the use of suitably occluded contact lens (Sivak,

Sivak & MacKenzie, 1985). In this manner, it has been possible to examine, in normal

subjects, the consequences of unilateral presentation of information over the course of an

extended movement. MacKenzie, Sivak and Elliott (1987) had subjects make relatively

slow positioning movements, with an unseen responding hand, to continuously displayed

target lights. All movements were made under monocular conditions, that is, one eye was

occluded. Through the use of appropriately positioned and partitioned contact lens', it was

possible to ensure that all but peripheral vision from a single visual field was effectively

blocked In a control condition, unrestricted central and peripheral vision of the entire

visual field was permitted.

Subjects were required to move an unseen knob to the perceived position of the

target light. The movement itself was highly constrained. The knob moved over a surface

directly beneath the target display board, and was free to move only in two dimensions.

Error measures were computed on the basis of the discrepancy between the XY coordinates

of the final position of the knob and the position of the target light. Constant error scores

were calculated in the direction of movement, and perpendicular to the direction of

movement. A measure of radial error was also assessed. As there were only two trials for each unique combination of conditions, there was no practical means of providing a

measure of variable error.

The most notable characteristics of the results were that directional constant errors

were of greater magnitude for the left hand when movements were made into both the left

and right visual fields. An overall tendency to overshoot the target seemed to be

independent of the hand making the response. In striking contrast however, subjects were

appreciably more accurate when making responses to the left section of the target board,

and when visual information was projected solely to the left visual field. This effect is again

consistent with the large body of research which suggests that there exists a right

hemisphere advantage for the localization of targets in extrapersonal space (e.g., Semmes,

Weinstein, Ghent & Teuber, 1963; Grusser, 1986; Hannay, Varney & Benton, 1976). The

trend seemed unaffected by the hand making the response (MacKenzie et al. 1987).

Also worthy of comment is the finding that localization accuracy did not vary

between the control and vision occluded conditions. Thus it appears that the availability of

foveal information contributed little to terminal accuracy in this task. This is not entirely

surprising, given that, vision of the responding hand was not available, therefore there was

no opportunity to conduct correction procedures on the basis of visual information of 7 8

Page 93: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

relative target and hand positions as the hand never entered foveal vision. The main role of

vision in this procedure, would appear to have been as an aid to the localization of the target

in extrapersonal space, which, if Paillard (1982) is correct, is accomplished primarily

through peripheral vision. It would then be of little surprise to note that the presence or

absence of foveal vision had little effect in this instance. It is this use of, what is

essentially, peripheral vision which may have contributed to the extent of the left hemi-field

and left external space advantage for target localization (c.f., Trevarthen, 1974).

The initial requirement for an estimation of the target position in extrapersonal space

may have represented a truly spatial task, as reflected by the left hemi-field advantage. The

actual execution of the locating movements was so highly constrained however (2-

dimensional movement on a planar surface) that no attenuation of a right hand advantage

would have been anticipated. In order to establish whether the right hemisphere advantage,

in terms of the localization of targets in extrapersonal space, impinges upon the

characteristics of the motor output, it is a prerequisite that tasks be considered which permit

an adequate expression of this presumed superiority (c.f., Guiard et al., 1983). As stressed

repeatedly (e.g., section 7.2), the utility of available visual information is multifaceted, and

is most clearly revealed when movements which have some ecological validity, such as

reaching and pointing, are examined. Conjunctively, the cooperative interaction of the

cerebral hemispheres is likely to be most faithfully reproduced when movements which

bear at least a passing resemblance to "natural acts" are adopted.

9.3 AN EVOLUTIONARY PERSPECTIVE

In a thought provoking review, MacNeilage, S tuddert-Kennedy and Lindblom

(1987) have called for a reconsideration of the evolution of the observed patterns of human

handedness. Drawing on an extensive collection of, previously disjointed, studies they

suggest that the evolutionary precursors of asymmetries in human upper limb action may be

detected through phylogical studies of extant subhuman primates (Glezer, 1987).

Challenging the pervasive view that the development of language is responsible for the

laterality seen exhibited in human handedness, MacNeilage et al. argue that the

development of manipulative functions lead to a subsequent left hemisphere specialization

which eventually served as the substrate for language acquisition. Central to this position is

the claim that there was a pre-existing right hemisphere specialization for the regulation of

reaching movements.

The authors suggest that the vestiges of this evolutionary progression may still be

observed in a number of species of monkey which continue to exhibit a left hand

Page 94: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

superiority and preference for reaching, accompanied by a right hand advantage for

manipulative functions. They suggest that, in monkeys left handedness for reaching may reflect a spatiomotor specialization of the right hemisphere related to the right hemisphere's visuospatial specialization in humans ... some residue of the spatiomotor specialization we attribute to prosimians and monkeys may be present in humans (and) is suggested particularly by the study of Guiard et al. (1983) (p. 258).

It is possible that the clearest exhibition of these trends indicates that "the initial

specialization may have been primarily for the use of visual information in preprogramming

of ballistic reaching movements" (p. 259). If one considers "preprogramming" to rather be,

the use of visual information prior to the initiation of movement, and that a "ballistic" action

is one which occurs in the absence of visually based corrections when the reaching hand is

in foveal vision, this perspective may be quite readily accommodated within the task

orientated approach which has been outlined.

Pivotal in consideration of the role of the right hemisphere in the regulation of any

movement is specification of the inherent spatial element. Peters (note 1) is probably not the

first to highlight that certain activities which, although obviously containing an important

spatial element, such as writing, are performed exclusively by the preferred right hand. It

may often be the case however that "motion of the right hand typically finds its vital spatial

references in the results of motion of the left hand" (Guiard 1987, p. 277). This is a

behavioural strategy which is certainly present within an infant's first weeks. Bresard and

Bresson (1987) recount their observations that a 5-month-old child will always fmt put its

left hand onto the edge of a tray, before using the right hand to retrieve objects from its

surface. Indeed, the study of the initial reaching movements made by human neonates, a

more explicitly ontological approach, has provided converging evidence that the initial

preference may be for reaching with what will eventually become the non-preferred left

hand (MacNeilage et al., 1987; Vauclair & Fagot, 1987). That this is initially not only a left

sided preference, but indeed also a superiority in terms of "open-loop" reaching for objects,

has been revealed by de Schonen and Bresson (1984). It is this initial left handed

superiority and preference which may provide some further indication of the cooperative

role of the right hemisphere in the regulation of goal directed action.

Clearly the magnitude or, more importantly, the functional significance of this

contribution is highly dependent upon the task structure. In view of the mutual

constrainment of action and perception, the extent to which this potential is realized will be

some function of both received environmental operators, be these visual or non-visual, and

the nature of the action they afford.

Page 95: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 10

EXPERIMENT 1

10.1 r n O D U C T I O N

Having conceived of observed manual asymmetries as reflecting a multitude of

transacting factors, it is perhaps only with some difficulty that one might specify the manner in which the relative involvement of these factors contributes to the outcome of goal directed action. As has been continuously stressed, tasks may not be considered

unidimensional, other than with respect to a unitary task goal, and as such, the

multidimensional nature of the asymmetries arising from the specific behaviour of the nervous system, and indeed from the behaviour of the organism per se, might only be

adequately revealed through a multidimensional examination of task execution rather than

through the use of some global measure. As a consequence, the possibility exists that the

"direction" of asymmetries across a "collection" of "appropriate" measures need not itself

be consistent and may vary as a function of both internal and external environmental

influences and "physical" constraints upon the "system". More tangibly, through the

experimental manipulation of task constraints, it should be possible to exert an effect upon

the behaviour of the nervous system such that, in moving toward the same action goal in

every instance, the asymmetrically balance may be altered in a way which may be detected

through the use of appropriate measures. As an illustrative example, consider that by utilizing tasks, some specific

components of which apparently require the involvement of the right hemisphere to a

greater extent, it should be possible to elicit manifestations of this differential involvement

upon appropriate dependent measures. More importantly, levels of this factor ought to

produce quantitatively different effects upon the dependent measure of interest, even

though the global task structure remains essentially unaltered

Tasks which have previously been considered unitary and often, as a consequence,

to "favour" the processing characteristics of one cerebral hemisphere over the other, may

potentially be subject to intervention of this hypothetical factor of interest on a subset of a

collection of experimental measures, reflecting an influence due to that particular factor

which does not directlv transcend all levels of the responding system. For example, by altering the levels of "spatial complexity" associated with a task, the appropriate dependent

measures will presumably reflect a covarying right hemisphere involvement. That is, the

extent of, for example, a right hand "advantage" should decrease as the requirement for the

processing of "spatial material" increases. Tasks which, for their satisfactory completion, 8 1

Page 96: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

require that individuals deal with complex spatial relationships appear then to be the most

likely candidates for inducing the required shift (c.f., Guiard et al, 1983). From the point of view of examining manual asymmetries, it is important that some

degree of interaction may be demonstrated. In the past this has been taken to mean that it is

sufficient to specify one task as "spatial" and another as "non-spatial" and as such that a dependent measure such as simple reaction time should directly reveal differential

hemispheric involvement. A problem arises however, when one attempts to use these tasks

as a basis on which to examine manual asymmetries. One must foremost ensure that a

"natural compatibility" persists. One simple approach has been to specify that a reaching

task is more spatially complex than, for example, a tapping task and associatively that the

reaching task may more favour the left hand than the right. Obviously a problem exists in

that these tasks are dissimilar in other respects, and revealed laterality effects may not justifiably be attributed to this one, though perhaps theoretically "alluring", factor of spatial complexity. Consideration of the location of a target in either two or three dimensions may

be one correlate of spatial complexity, yet the use of such a manipulation necessarily

invokes discontinuities of the response movement. Whilst highlighting again, in line with successive theorists (e.g., Gibson, 1950;

Lee & Thornson, 1982), the functional unity of the perceptual and motor systems, it is

essential that for any adequate examination of the role of "spatio-perceptual" asymmetries

with respect to motor control, spatial complexity can be manipulated independently of, for instance, target location.

That this equivalence has proved d=cult to achieve is perhaps one reason why the

issue of spatial complexity has received relatively little consideration in this regard. As

discussed, Guiard et al. (1983) employed a single task structure which, it was postulated,

required processing of a spatially complex nature. However no consideration of levels of

complexity was entertained. It is thus necessary to establish some means of equating the

motor response, whilst manipulating the complexity of the perceptual processing that an

individual must accomplish, in order to establish the desired tenninal location of that

response in extrapersonal space.

Such an approach might initially appear to place the onus of asymmetrical influence

of spatial complexity upon the initial establishment of target position, rather than in terms of

a differential influence exerted during the course of the response movement as such.

Indeed, Fisk and Goodale (1985) argue that "the kinematics of the reaching movement are

most closely related to processing differences in neural systems associated with motor

output after the spatial location of the target has been specified by other neural systems" (p.

177). However, in emphasizing the importance of the action/perception coalition (Turvey, 8 2

Page 97: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

1977), and while continuing to maintain that particular measures may be uniquely sensitive

to effects exerted at particular locii within the nervous system, it is unlikely that something

as broadly defined as the "kinematics of movement" will be unaffected by factors relating to

the localization of a target in space. It is misleading to equate the apparent temporal

distinctiveness of external events with associated characteristics of the responding system, the process is, at least in some sense recursive (c.f., Hofstadtter, 1979).

Those tasks which have previously been employed to sample the supposed right hemisphere superiority for the manipulation of spatial relationships have conventionally been "static" rather than "kinetic". As detailed in Chapter 2, these have included intra and

inter-modal matching of patterns. Young and Ellis (1979) were able to demonstrate a left

hand, and presumed right hemisphere advantage for the tactile detection and enumeration of braille dots arranged in a complex spatial pattern, whilst no such between hand differences were evident for dots presented in "predictable" straight line patterns.

In an effort to examine a spatial task of a kinetic, and thus ecologically valid, nature

Eals (1987) gave some consideration to asymmetries in the perception of "apparent movement". The task required prediction of the final location of a dot array from a series of

brief presentations simulating a pattern transition. Individuals were required to predict the spatial array which would occupy the next position in a sequence. Response accuracy was

found to be superior for those sequences presented briefly to the left hemi-field and thus

initially to the right hemisphere. It appears that the right hemisphere demonstrates superiority both of the appreciation of an initial spatial array (Young & Ellis, 1979) and extrapolation to a spatial and temporal displacement of that array (Eals, 1987). In a related

vein, Freyd (1983) has suggested that "mental representation of movement is a fundamental

organizing principle for human perception and cognition" (p. 575) and has provided

evidence that individuals are adept at representing implied motion when static stimuli are

observed, in turn providing convergence with the "classical literature" in which apparent

motion may be perceived from what may only be a flickering of two or more stimuli

separated in time. In normal subjects, the relationship of brain lateralization to perceptual and

visuospatial capabilities is conventionally investigated through the use of brief,

tachistoscopic presentations of stimuli to either the left or right hemi-field (Eals, 1987). In

circumstances in which the duration of presentation is brief, subjects are unable to initiate

an eye movement prior to the offset of the stimulus.

The rational for using such presentations is based upon the anatomical

characteristics of the visual system, specifically that projections from the temporal

hemiretinae to the visual cortex are contralateral, whereas those from the nasal hemiretinae 8 3

Page 98: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

are ipsilateral. The consequences of this arrangement are that stimuli presented to the Right

visual field have direct access to the Left Hemisphere and those presented to the Left hemi-

field have an equivalent relationship with the Right hemisphere (Sergent, 1983).

The assumption that cerebral processing of the stimulus related information

commences in a single hemisphere, that contralateral to the receiving hemifield, may be

justified only in circumstances in which the stimulus is presented to either the left or right

of fixation and outside of foveal vision, that is presented at least one degrees eccentric of

the point of fixation, and when stimulus duration is 150 ms or less (Sergent, 1983). If

these conditions have been met, there is some justification in concluding that "perceptual

superiority" of the contralateral hemisphere is at least partially reflected in appropriate dependent measures (Eals, 1987).

In this initial experiment, an attempt was made to examine the assumption that the localization of a target in extrapersonal space, which is itself conceived of as a process involving spatial manipulations, is accomplished in superior fashion by the right

hemisphere. As a corollary of this, it was hypothesized that the more complex the spatial

manipulations required, the greater would be the magnitude of the right hemisphere advantage. That is, some degree of interaction was anticipated.

There is of course evidence that factors relating to "spatiality" pervade all aspects of goal directed action, and are not constrained to act upon what might have previously been

termed, initial perceptual processing. Spatial compatibility effects (see Chapter 4.3) are one striking demonstration of this tendency. This study also amounted to a partial replication of the Fisk and Goodale study of 1985, in which was conducted a detailed analysis of the

spatial and temporal organization of unrestricted reaching to punctiform targets. The findings revealed that the difference in the time taken to initiate contralateral movements

was, on average, 23 ms longer than the time to initiate ipsilateral reaching movements. This

Hand by Visual Field interaction was also reproduced for movement time. although the

amplitude of the movement was equivalent for ipsilateral and contralateral reaches. Thus,

this experiment represents the first part of a preliminary attempt to examine the influence of

spatial factors (broadly defined) upon the characteristics of visually guided, goal directed

reaching.

Page 99: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

10.2 METHODS

SUBJECTS

The subjects were eight, naive, male volunteers, each of whom were paid $10.00

for their participation. Individuals were all classified as right handed, on the basis of a

previously administered Edinburgh Handedness Inventory (Oldfield, 1971). All subjects

had normal or corrected to normal vision.

APPARATUS FOR DATA COLLECTION

The subject was seated facing a 50 cm by 50 cm display panel. The distance from

the subject's eyes to the screen was approximately 50 crn. The panel was constructed in a

fashion such that a 21 by 21 array of red LED'S (centres spaced by 2 cm in the horizontal

and vertical directions) was not normally visible behind a translucent perspex sheet.

Activation of a single LED resulted in the back projection of light onto the perspex sheet,

which was viewed by the subject as point source of light. The position of the central light

of the array represented the fixation point, and was located directly in front of the subject at

eye level.

The forefinger tip of the subject's responding hand was covered with a rubber

thimble, upon which was mounted a small membrane microswitch. Both the microswitch

and the LED array were interfaced with an Apple IIe microcomputer, in which was installed

a Mountain Hardware Apple Clock. The status of the microswitch (open or closed)

constituted a single bit input. When the thimble was placed upon the starting platform,

located on a virtual line between the centre of the display panel and the subject's midline,

40 cm from the surface of the panel and 40 cm below the fixation point, the microswitch

was in a closed position. On leaving the starting position, upon movement initiation, the

status of the switch was reversed, and remained so until the subject made contact with the

surface of the display panel.

The control program was a combination of Applesoft BASIC and 6502 assembler

language. The assembly routines were used for the low level control required to achieve

millisecond timing of LED display onsets and offsets, and of changes in switch status (c.f.,

Gardiner, Franks & Goodman, 1987).

The only illumination provided in an otherwise light free, black walled room, was a

single 100 watt lamp, located behind the display panel to reduce both shadows and

reflections upon the perspex sheet. 8 5

Page 100: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

The figure presented below gives some indication of the arrangement of significant

components.

FIGURE 10A Schematic representation of the position of the subject relative to the display

panel.

MATERIALS

The test materials consisted of four, five point symmetrical patterns, comprising

linear, quadratic, cubic and quartic functions (Appendix A). In the experimental

application, the first four dots in the sequence were presented, subjects were required to

predict the position of the final dot. For a given collection of four patterns, the position of

Page 101: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

the final dot was equivalent, that is the x-z coordinates (where z represents the vertical axis)

of the last dot were always the same for all patterns. Indeed the x coordinates of each

pattern were also always equivalent, referring to a positive or negative temporal

progression along the x axis. Thus, although the global characteristics of each pattern were

distinct, the differences were accounted for entirely by the values of the respective z

coordinates for dots one to four. It was the non-presented final position which constituted

the target, and as can be seen, although the pattern and presumed "complexity" were

different in each case, an appropriate response, that is a movement to the extrapolated final

position, would be identical in all instances. Eight "phantom" final positions were

employed in this experiment, four to each side of the vertical midline of the panel, and

associatively, four to each side of the horizontal midline of the panel (Appendix B). As the

subject fixated at the intersection of these axes, there was a corresponding variation of

target position by visual field. It was possible for the target sequence to appear in one of

four possible orientations, all terminating at a single final point (referenced to one of eight

positions on the board corresponding to what would have been the final dot in the

sequence). In actuality, and for a given target position, a single display orientation was

used.

In accordance with the correspondence of the final target position to the panel

reference axes, each of the eight targets could be specified in terms of; the Visual Field to

which the display was presented, left or right, the position of the target relative to the

virtual horizontal line passing through the fixation point (hereafter referred to as the

Midpoint) i-e., above or below, the position of the target relative to the virtual vertical line

passing through the futation point (hereafter referred to as the Target Eccentricity).

Two values of Target Eccentricity were employed in this experiment, the final target

position being either 60 mm or 120 mm outward from the fixation point, representing 6.84 and 13.50 degrees of visual angle respectively. With respect to the relation to the Midpoint,

targets were 6.84 degrees of visual angle above or below the fixation point. In all instances

the orientation of the patterns was such that with respect to the vertical virtual axis, patterns

terminating in a target 6.84 degrees eccentric commenced 13.50 degrees eccentric and

progressed towards the axis, whereas for targets 13.50 degrees eccentric, the first dot in

the display was 6.84 degrees eccentric, with the sequence progressing away from the axis.

Patterns were thus always displayed in the visual periphery.

Five independent variables were utilized; the Hand making the response, the Visual

Field in which the pattern was displayed, the Pattern displayed, the position of the

"phantom" target in Relation to the Midpoint, and the Target Eccentricity. A repeated

measures design was employed, with levels of Visual Field, Pattern, Relation to Midpoint 8 7

Page 102: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

and Target Eccentricity randomized within blocks by Hand, a 2 x 2 x 4 x 2 x 2 factorial

design.

In their physical realization, pattern sequences took the form of sequential

illumination of the appropriate LED'S such that; the first light was on singly for 37.5 ms,

the first and second lights were phased, so as to appear to be on simultaneously, for 37.5 ms, the first, second and third lights were phased for 37.5 ms, and finally all four lights

were presented simultaneously for 37.5 ms. Thus the appearance was of a spatial and

temporal progression, of duration 150 ms

Subjects were given no advance indication of the nature of the patterns, other than

to be informed that the patterns were symmetrical about the third dot, though not

necessarily forming a mirror image. The subject's were also told that the order of

presentation would help them to establish the position of the final dot.

PROCEDURE

Prior to the session itself, subjects were instructed on the importance of maintaining

fixation until the presentation of the stimulus sequence. Subjects were encouraged to lift

their finger from the starting position if they became aware of making an eye movement.

This had the practical effect of terminating that particulat trial, any such trials were

subsequently repeated.

Test sessions consisted of four blocks of 96 trials, two blocks with each

responding hand, preceded by two blocks of 32 practice trials. The subject was asked to

use his index finger, upon which the thimble was placed, to point to the place on the

display panel which he felt corresponded to the position which would have been occupied

by the final dot in the sequence. Individuals were asked to respond as quickly and as

accurately as possible. Each unique combination of, the Visual Field in which the display

was presented, the Pattern displayed, the position of the target relative to the Midpoint of

the panel, and the Eccentricity of the Target, appeared on three occasions within each

block. For half of the blocks, subjects responded with their left hand and for the other half

with their right hand. The order of hand use conditions was counterbalanced across

subjects. All trials began with a microcomputer generated tone initiated on the experimenters

command. Upon subsequent closure of the thimble microswitch on the starting platform,

the central fixation light was illuminated. Subjects were required to fixate upon this position

until, after a variable interval (of between 500 and 3000 ms) the fixation was extinguished.

Simultaneously the onset of the pattem display was initiated. Random foreperiods reduce 8 8

Page 103: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

the probability of anticipatory responses and ensure against eye movements which have

been timed to coincide with stimulus onset. A trial was terminated when the subject

completed his movement to the display panel. There was a break of approximately five

seconds between trials. Reaction Times, assessed as being the time from the onset of the pattern sequence

until movement initiation (when the microswitch was first opened), and Movement Time,

the time between movement initiation and contact with the surface of the display panel, were automatically calculated for each trial, and were saved to floppy disk on the

completion of each block. The test session lasted approximately 70 minutes. Subjects were permitted rest period between blocks, as required.

Page 104: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

10.3 RESULTS

MEDIAN REACTION TIMES

Median Reaction Time measures were obtained from each cell of the 64 unique

combinations of five factors, each summary median value was derived from six trials. A

repeated measures ANOVA was performed, this was a 2 x 2 x 4 x 2 x 2 factorial design

with Hand (Right, Left), Visual Field (Left, Right), Pattern (1,2,3, & 4), Relation to

Midpoint (Lower, Upper) and Target Eccentricity (Inner, Outer) as factors.

Although a left hand advantage, in terms of reaction time, was exhibited by six of

the eight subjects, and there was an overall "left hand advantage" when the results were

collapsed across all subjects, this effect failed to reach statistical significance. It is likely

that the characteristic response pattern of one of the "right hand advantaged subjects,

D.T., in particular, had some considerable influence on this distribution. This subject

exhibited a right hand response latency which was, on average, 64 ms more rapid than that

for the left hand. As it was, the apparent effect of Hand was some way from reaching

statistical significance, F(1,7) = 0.55, p > 0.05.

TABLE 10.1 Median Reaction Time (ms) as a Function of Hand and Visual Field

Hand

Visual Field

Left Right mean

Right

Left

mean 406.5 402.3

Page 105: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL F L D

RIGHT

VISUAL FIELD

FIGURE 10.1 Median Reaction Time (ms) Hand by Visual Field

Although there was a marginal advantage for sequences presented to the right visual field,

this was, similarly, not of statistical ~ i ~ c a n c e , F(l, 7) = 2.21, p > 0.05. There were, in

addition, no statistically significant main effects for the factors pertaining to the relationship

of the target position to the central fixation point, there was no main effect associated with

Midpoint or with Target Eccentricity. It is of interest however that there was apparently

some relatively consistent effect on reaction time associated with the pattern which was

initially presented, this supposed effect marginhy failed to reach statistical significance,

F(3,21) = 3.02, p = 0.053. Although it is inappropriate to conduct formal post hoc

analysis on these data, inspection of the means provides some indication that responses to

pattern 4 were appreciably slower than those to the other sequences. Indeed the trend in

terms of latency was consistent across both responding hands.

Page 106: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 10.2 Median Reaction Time (ms) as a Function of Hand and Pattern

Pattern

Hand 1 2 3 4

Right 403.3 402.0 408.2 422.8

Left 395.0 391.8 397.5 414.4

mean 399.3 396.9 402.9 418.6

These trends in the means are illustrated by Figure 10.2.

HAND BY PATTERIV

RIGHT HAND LEFT HAND

FIGURE 10.2 Median Reaction Time (rns) Hand by Pattern

Page 107: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

There was an absence of any higher order interactions of statistical significance for the

reaction time measure.

Page 108: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

MEDIAN MOVEMENT TIMES

As for the Reaction Time measures, Median Movement Times were obtained from

each cell of 64 unique combinations. A 2 x 2 x 4 x 2 x 2 factorial design repeated measures

ANOVA was performed Hand, Visual Field, Pattern, Relation to Midpoint and Target

Eccentricity were again factors. Preliminary analysis revealed no main effects associated

with the factors of Hand, F(1,7) = 0.23, p > 0.05, or of Visual Field, F(1,7) = 0.03, p > 0.05, but did indicate the presence of a statistically sigmficant interaction of these factors,

F(l, 7) = 61 .25, p c 0.0001. As is clearly represented, both in Table 10.3 and Figure 10.3, right hand responses were made more rapidly when directed toward patterns

presented in the right visual field, than those made when sequences were presented in the

left visual field, similarly ipsilateral left hand responses were of shorter duration than left

contralateral responses.

TABLE 10.3 Median Movement Time (ms) as a Function of Hand and Visual Field

Visual Field

Hand Left "T mean

Right 421.5 404.3 412.9

Left 411.1 427.6 419.4 I

mean 416.3 416.0

Page 109: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL FIELD 430 -I

RIGHTHAND LEFTHAND

RIGHT

VISUAL FIELD 1

FIGURE 10.3 Median Movement Time (ms) Hand by Visual Field

The analysis also revealed the presence of a statistically significant main effect associated

with the factor of Pattern, F(3,21) = 3.37, p c 0.05. This did not appear to parallel the

trends in Reaction Time indeed, although post hoc pairwise analysis of means using the

Tukey HSD procedure (Table 10.4b)revealed.the only pairwise difference that reached

statistical sigruficance was that between patterns 1 and 4, inspection of the pattern of means

indicates that the median movement times to targets specified by pattern 1 were appreciably

shorter than those specified by other patterns. Figure 10.4 provides a graphical portrayal of

this effect. Comparison of equivalent values for Reaction Time would suggest, as

outlined,that it was responses to pattern 4 which were noticeably slower to be initiated in

that case.

Page 110: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 10.4 Median Movement Time (ms) as a Function of Hand and Pattern

Pattern

Hand

Right

Left

mean 395.4 419.6 420.9 428.6

TABLE 10.4b Median Movement Times (ms) Differences among Means

Page 111: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY PATTERN

RIGHT HAND LEFT HAND

FIGURE 10.4 Median Movement Time (ms) Hand by Pattern

There was also provided confirmation of intuitive expectations that movements of

greater absolute amplitude, those made to above the midpoint, would be associated with

longer movement times, F(l, 7) = 52.57, p < 0.0002. There was however no main effect

associated with Target Eccentricity, F(l, 7) = 0.27, p > 0.05, nor an appreciable interaction

of these factors nor indeed any strong evidence for any other second order interactions.

TABLE 10.5 Median Movement Time (ms) as a Function of Hand and Relation to

Miduoint.

Midpoint

Hand Lower Upper mean

Right 399.3

Left 407.8

mean 403.5 428.7

Page 112: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY RELATION TO MIDPOINT

LOWER UPPER

MIDPOINT

FIGURE 10.5 Median Movement Time (ms) Hand by Relation to Midpoint

In addition, there was observed a statistically significant higher order interaction,

that of Hand by Field by Target Eccenmcity, F(l, 7) = 8.18, p c 0.05.

TABLE 10.6 Median Movement Time (ms) as a Function of Hand. Visual Field and

Target Eccentricity.

Target Eccentricity

Inner Outer

Visual Field Left Right Left Right mean

Hand

Right 413.9 412.1 429.2 396.5 412.9

Left 412.2 423.5 410.0 43 1.7 419.4

mean 413.1 417.8 419.6 414.1

Page 113: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

As is revealed by inspection of Figure 10.6 the interaction reflects a tendency for

movements made by both hands to be completed more rapidly when directed at Outer, more

eccentric, targets only when responses were ipsilateral, that is when the responding hand

was moving into "its own" visual space. When movements were conualateral, movement

times were shorter for Inner targets.

HAND BY VISUAL FIELD BY ECCENTRICITY

"201

R.H. (L.V.F.) R.H. (R.V.F.) L.H. (L.V.F.) L.H. (R.V.F.)

390 ! I 1 . INNER OUTER

ECCENTRICITY

FIGURE 10.6 Median Movement Time (ms) Hand by Visual Field and Target

Eccentricity.

Page 114: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

10.4 DISCUSSION

Somewhat contrary to expectations, Median Reaction Time measures provided few

consistent indications as to effects arising as a consequence of experimental manipulations.

With regard to the slight left hand advantage in terms of reaction time, the trend is thought

provoking rather than by any means conclusive. The measures of reaction time obtained

were characterized by large bekeen and within subject variability which is likely to have

contributed somewhat to the absence of statistically sigdicant main effects. Although the

magnitude of the overall left hand advantage was largely attenuated by the right hand

advantage exhibited by subject D.T., one cannot assume that the distribution, in this single

case, was due to anything other than chance. Conjunctively, although the trend toward an

overall right visual field advantage for reaction time is counterintuitive, beaxing in mind the

supposed nature of the stimulus materials, the tendency was not of sufficient consistency to

make it worthy of detailed comment.

In contrast, the main effect associated with the stimulus pattern, albeit marginally

failing to surpass the conventional criterion value for statistical sigdicance, does appear

notable. The increase in response latency associated with Pattern 4 was symmetrically

expressed across responding hands, which might, in itself, initially suggest that the

increase was not necessarily due to an increased complexity of spatial processing as suph.

It is perhaps of salience that the constituent points within Pattern 4 were more spatially

disparate than those within other patterns. The increased reaction times may reflect the

additional time required to assimilate information from a greater area of the visual field,

though this is somewhat conjectual. A perhaps related, and certainly likely, possibility

exists, that the nature of certain patterns were such that the global characteristics of the

sequence were not readily apparent. There was some concern that subjects were, rather

quickly, resorting to guesses as to the nature of each pattern, thus effectively negating the

intended manipulation of spatial complexity. In these circumstances it is possible that,

having formulated some heuristic as to the presumed terminal position of a particular

sequence, "secondary" factors such as the spatial distribution of display points assume

greater significance. Indeed, post-experimental debriefings indicated that this may indeed

have been the case. Rarely did subject's assignations of, in particular, patterns 3 and 4

correspond to the actual sequences.

It had previously been suggested by this author that a sufficient target display series

would be that which elicited an interaction with either responding hand or visual field of

presentation. On reflection, it seems there may be no justification for the post hoc selection

of tasks considered appropriate for a particular application simply because they were

successful in producing some form of asymmetrical response. Rather, there may only be a 100

Page 115: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

priori specification of that which, it is hypothesized, represents some manipulation of a

variable of interest, in this case spatial complexity. Or rather more specifically, the spatial

complexity of sequence, the assimilation of which is a prerequisite for the establishment of

a target position in space. Assessment of the appropriateness of this specification is then, at

least in part, an empirical enquiry. Therefore, it does appear that only by making subjects

explicitly aware of the relative complexities of the patterns might one be relatively assured

that, at least, the desired manipulation was being applied, and thus that the desired enquiry

could be realized.

In terms of reaction time measures, there was no indication of spatial compatibility

effects, ipsilateral and contralateral movements were initiated with equivalent latencies.

There was thus a failure to replicate the findings obtained by Fisk and Goodale (1985), who employed a somewhat similar reaching task, or the results reported by, among others,

Anzola, Bertoloni, Buchtel and Rizzolatti (1977) using a less complex reaction time

paradigms. One cannot make appeal to the high variability of the reaction time measures

obtained in this experiment, there were few indications that a spatial compatibility effect

was present. The trends in means indicated that left hand contralateral reaches were, if

anything, initiated more rapidly than ipsilateral reaches.

The responding hand by visual field interactionj which was clearly evident in the

dismbution of Movement Time latencies, appears entukly consistent with previous work 1

highlighting what are assumed to be spatial compatibility effects (e.g., Fisk & Goodale,

1985). Ipsilateral movements were completed a good deal more rapidly than contralateral

equivalents. It should be noted, of course, that the me absolute distance between the

starting position and the target was equivalent for of response.

It is of some interest to note that, in this instance, responses made by the right hand

were not appreciably, or at least consistently, more rapidly completed than lcft hand

movements. Similarly responses made into one half of v i s u W y centrcd space were not

favoured over responses made into the other.

The main effect for Midpoint is, in itself, of little interest, other than in providing

some substantiation of intuition that the time required to complete a response was at least

some correlate of movement amplitude. However, a consideration of the apparent

interaction of Hand by Visual Field by Target Eccentricity, provides some convergence

with evidence for the presence of a spatial compatibility effect, in that it is clearly not the

case that movement duration is solely determined by the absolute distance between the

starting position and the target. In this case, iusilateral responses made to outer targets

consumed less time than those made to inner equivalents, although this tendency was less

clearly expressed for the left hand. Contralateral movements made by either hand were of 10 1

Page 116: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

longer duration when made to the more eccentric outer targets. As with the Hand by Visual

Field interaction, the variations in movement time cannot be attributed simply to the

distance through which the responding hand is required to move in completing the

movement. The possible factors underlying these effects will be considered in greater detail

in discussing the results of Experiment 2. It did appear that, in this experiment, the manipulation of spatial complexity,

through the use of various display patterns, was ineffectual, as subjects were rarely actually

aware of the nature of each pattern, and imposed their own best guess as to pattern

characteristics. As has been discussed however, asymmetries in motor behaviour may only

adequately assessed through the use of a range of dependent measures, each of which is

assumed to have at least some, rather specific sensitivity. Reaction Time and Movement

Time may only be regarded as gross indicators, in this context.

Experiment 2 was designed to implement this multifactorial examination of

asymmetries in pointing behaviour, and also conducted with a view to more forcefully

imposing manipulations of spatial complexity, examining in greater detail what were

presumed to be spatial comp~tibility effects and considering, in particular, the related

contribution of information of a visual origin to the regulation of goal directed pointing

movements.

Page 117: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

CHAPTER 11

EXPERIMENT 2

1 1.1 INTRODUCTION

In that it is the case that behavioural asymmetries are the manifestation of a complex

transactional process, it is similarly apparent that action, or overt behaviour itself, is merely

one aspect of an animal-environmental mutualism or synergy (Kugler, Kelso & Turvey, 1982). One other pivotal input to this synergy is the perception of the space into which any

action will be directed In emphasizing the exigency of the perception of space, one can detect the central role this function must assume in both the ecological approach to perception and action, and themore mechanistic computational approaches. Thus one can

find some initial cause to emphathise with Morasso and Tagliasco (1986) who,in detailing the requirements for a "global motor control system" outline that movement must be:

the final result of a plan of interaction of the body with the environment. The initial prerequisite for the Central Neural Controller is the representation of space, of the objects, of their mutual relationships as well as their relationships with the self (p. 243).

One must surely distinguish however, between representing ones surroundings or external space, and some extant geometric representation which is the "initial step for the motor

control system and thefinal step for the vision system" (Morasso & Tagliasco, 1986, p. 243, this author's italics). Indeed there are immediate contradictions in an approach which also encapsulates the proposal that:

such a representation communicates bidirectionally with the motor and visual systems ... does not drive the motor system in a purely top-down fashion but is refined and updated by it during the motor performance (and that) the visual system does not generate the geometric representation in a purely bottom-up fashion but is driven by it, in a recursive way, taking into account at each instant the current representation (p. 243).

A number of theorists have expressed fundamental objections to this form of

computational representation of the environment, or more specifically that of space. Turvey

and Carello (1986) argue that theories and experiments focussing on space as a

mathematical consmct within the context of a Cartesian Coordinate system are, whilst

appealing, unlikely to reflect that which organisms must percieve as functional

characteristics of, or affordances within, their environment. In a similar vein, the

"ecological perspective" exorcises the requirement for a third class of terms or level of

discourse (c.f., Searle, 1984), encapsulating intermediate "pseudoconstructions" such as

representations and programs, which a computational approach must include as a means to

mediate between the animal and the environment (Kugler, Kelso & Turvey, 1982).

103

Page 118: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

The term recursive can in itself be misleading when referenced to the modification

of a representation rather than the global characteristics of an action per se. Alternatively, if

one adopts a sensitivity to the nature of the environmental information which defines the

goal of any relatively discrete action, then it is legitimate to enquire as to the effect the nature of this information will have on the characteristics of the resultant action. For

example if the same action goal is specified by a variety of environmental operators, or

more specifically stimulus energies, differences in the optical flow fields, is the appropriate

goal directed action likely to exhibit the same characteristics in each case? It is in this sense that the potentially recursive nature of goal directed action assumes practical significance. The environmental information specifying an action goal may exert its effects throughout

the time course of and upon all behavioural manifestations of, the responding system, that is its influence may recur. As with the examination of behavioural asymmetries it is a

requirement that there be a multifactorial examination of goal realizing action. The

assumptions underlying this approach may be usefully contrasted with the conclusions

drawn by Fisk and Goodale (1985), that the spatial location of the target is specified by "neural systems" prior to those.more specifically associated with "motor output" and as

such that this specification is not reflected by kinematic measures. Of course, this recursion, if it indeed occurs, may or may not be expressed asymmetrically, this is then a related topic of enquiry.

In the experiment 1, and as discussed, there could have been little assurance that the

task goal was indeed the same in every instance, as subjects appeared to make their own best estimation as to the nature of the presented pattern. By insuring a prior familiarity with

the relevant patterns it should be possible to maintain an equivalence of task goals across

sequence presentations, in addition to applying the desired manipulation of spatial complexity. Application of the same task goal in each instance, through the continued use

of identical target locations, allied with manipulation of "complexity", may represent the

required systematic variation in environmental information, the forms of which afford

specification of a single goal.

In considering the multidimensional contribution of visual information to the

regulation of goal directed action, it is of course not the case that this contribution is limited

to the initial or continuing specification of the target goal (see Chapter 7). Whilst Prablanc,

Pelisson & Goodale (1986) provided indications that, even discontinuous, visual

information regarding the position of the target has action guiding functions for movements

which are not seen, Conti and Beaubaton (1976) have shown that visual information

pertaining to the position of the hand is utilized through various portions of the movement

trajectory. There has, however, been no prior investigation of whether vision of the 104

Page 119: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

responding hand, during the course of movement, continues to have a regulating function

when the position of the target is never actually seen but is merely implied. There is

certainly evidence that speed accuracy relationships are maintained in the absence of vision

of the hand (Prablanc, Eschallier, Komallis & Jeannerod, 1979), whereas Pelisson,

Prablanc, Goodale and Jeannerod (1986) suggest that modification of movement

trajectories in the absence of ambient illumination may be on a "pseudocontinuous" basis.

Clearly the nature of movement regulation in the absence of motion related visual

information or indeed the potentially non-discrete utilization of such information is still a

subject of enquiry.

Through manipulation of the ambient illumination present throughout the course of

the pointing movements previously described in Experiment 1, and by employing the

appropriate dependent measures, it may be possible to obtain some indication of the manner

in which visual information is utilized, both in defining the goal of that action and when

pertaining to the motion of the responding hand, in the regulation of ongoing movement.

The required manipulations are relatively straightforward to apply. As outlined, patterns

may be displayed which define the position of a punctiform target, the action goal, without

there being the need to explicitly represent that target, providing the individual is aware of

the implied relationship. The presence or absence of motion related visual information may

be controlled simply by altering the ambient illumination which is present throughout the

course of the movement. The appropriate dependent measures will obviously be a

multifactorial collection of behavioural and kinematic indices which, it is assumed, reflect

various aspects of the regulatory processes. These measures should perhaps be considered

as diagnostics rather than as representing specific stages within a "motor control process"

(c.f., Guiard, Diaz & Beaubaton, 1983). Thus Constant Error cannot simply be considered

as indicative of the accuracy of "central programming" any more than Variable Error may

be a reflection of the accuracy of "motor program execution". As discussed in Chapter 10,

the execution of a movement unaccompanied by identifiable and discrete modifications does

not imply the existence of a motor program.

There can be no doubt that measures such as Movement Time, Reaction Time,

Constant Error and Variable Error are salient pointers. The ultimate objective should

perhaps be to relate systematic variations on these measures rather more directly to the

presumed physiological substrate without recourse to a "third class of terms". Thus one can

permit descriptions at the phenomenological level, which may potentionally be related to

descriptions at the physical level without the need for intermediates.

Brooks (1974) has discussed how the relative continuity of movements may be

assessed, or diagnosed, through the measure of Zero Crossings of the Acceleration Profile, 105

Page 120: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

if there is obtained a kinematic description of the movement. This then represents a formal

distinction between what are otherwise similar movements. Continuous movements have

been described as those which are "quick and smooth" exhibiting only one velocity peak, to be contrasted with discontinuous "equivalents" revealed by the presence of multiple

crossings of the zero line by the acceleration trace, for which "motor commands for successive steps are supposed to be given only after intermittent referral to peripheral and central information" (Brooks, 1974, p. 306). In an attempt to provide an explanation at the

physicaVphysiological level, it has been suggested (Eccles, 1967) that continuous control,

or rather regulation, is subserved by cerebellar influence associated with spinocerebellar

and cerebrocerebellar projections.

However, descriptions of the characteristics of the overt movement, at the

phenomenological level need not be related directly to some physical or physiological correlate. Thus it is quite legitimate to describe variability in the terminal locations of motor

acts, over the course of a series of trials, without there being the need to ascribe this

variation to some manifestation of a motor program. It has been suggested (e.g., Annett,

Annett, Hudson & Turner, 1979) that the difference between the hands lies in the

variability of, or noise associated with, the initial production of force. This may, in theory,

be simply tested. By examining the Jerk, the third derivative of displacement, associated

with an evolving movement, that is the rate of change of acceleration with respect to time

and therefore an index of the variability of Force, prior to peak velocity (if this may be

described as "initial"), one may obtain a direct measure of this variability. This measure

may of course be assessed independently for each hand Similarly, a measure of the

variability of the time taken to reach peak velocity may provide an indirect indication of the

variability in the production of force. The peak velocity attained is likely to be some

measure of the magnitude of the initial impulse. Examination of the overt characteristics of movement may therefore provide useful information as to the nature of the regulation of such movement, without there existing the need for recourse to some "third level"

collection of terms.

The experimental strategy was to have subjects perform goal directed pointing to

phantom targets, the position of which had been implied by the presentation of a stimulus pattern (the nature of which was known to the subjects), when these movements were

performed to a variety of target locations, by either hand, with and without the presence of motion related visual information during the course of the movement. The overt

characteristics of these movements would be examined in tenns of a collection of dependent

measures with a view to obtaining some indication of the manner in which these

movements were regulated. In addition to the measures of Reaction Time and Movement 106

Page 121: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Time employed in Experiment 1 and the kinematic indices described above, Radial Error, a

measure of the absolute discrepancy between the terminal location of the movement and the

target position, Constant Error in the direction of the X and Z axes of the display board and

associated measures of Variable Error were to be assessed.

Page 122: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

11.2 METHODS

SUBJECTS

The subjects were eight, naive, male volunteers, each of whom were paid $10.00

for their participation. Individuals were all classified as right handers on the basis of the

Edinburgh Handedness Inventory (Oldfield, 197 1) which had been administered

previously. All subjects had normal vision.

APPARATUS FOR DATA COLLECTION

In this experiment, all reaching movements were recorded using a WATSMART motion analysis system. This is a 3-dimensional digitizing system which, by means of post

hoc reconstruction of 2-dimensional coordinates from two cameras, provides 3-

dimensional coordinates of reference markers.

Data acquisition requires the attachment of small infrared light emitting diodes to the

surface of the object or, for example body segment, the motion of which is of interest. The

marker LED's are pulsed in sequence at very high frequencies, as each marker is briefly

active, it is registered by custom cameras as a point source of light. These point sources are

digitized as 2-dimensional coordinates, and stored for subsequent transformation.

The display panel was that used in Experiment 1, a single modification was the

addition of 2 WATSMART infrared LED's which were aligned with the vertical (z), and

horizontal (x) axes of the panel. These were mounted upon the upper horizontal and left

vertical surfaces of the display panel, such that one marker was positioned to lie along the

same x coordinate axis as the central fsation point, while the other was located to lie along

the z coordinate axis of this point.

Subjects responded using a hand-held stylus, constructed from the plastic outer

barrel of a 10 ml syringe. On the tip of this stylus was placed a membrane microswitch,

mounted upon which was a rubber coated metal tip approximating the shape of a cylinder,

of dimensions, height 4 rnm and diameter 2 mm. A single WATSMART LED was attached

7.5 rnm above and behind this tip. The stylus was covered with a tape wrapping which also

served to indicate the part of the stylus to be gripped. The stylus microswitch was

interfaced with an Apple IIe microcomputer in the manner previously described. Infrared

LED's were interfaced with the WATSMART system.

The WATSMART cameras were positioned 1.8 m apart, 2.5 m from the ground , and a perpendicular distance of 2.1 m from the display panel with the respective viewing

108

Page 123: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

fields converging between the subject and the panel. From the subject's perspective, the

cameras were positioned over his right and left shoulders. During the practice trial blocks,

it was verified that the stylus tip could be "seen" by both cameras when located at the

starting position and at the termination of the movement. The camera positions were

calibrated immediately prior to each experimental session.

The Apple IIe microcomputer was used as an external trigger to initiate and

terminate the collection of data by the WATSMART system. Connected via the annunciator

ports of the Apple, and controlled by a 6502 assembler subroutine, WATSMART data

collection was triggered by the initial change of status of the stylus microswitch when the

subject initiated a movement and was halted upon the next change of switch, when the

stylus tip made contact with the display board. In all trials, data was sampled at 400 Hz.

Ambient illumination within what was an otherwise completely dark, black walled

room, was provided by a Kodak Carousel 600H projector, containing a 300 watt light

source. The beam of light produced was diffused and projected onto the ceiling above the

subject. The projector was shuttered by a, normally open, Lafayette Instruments Model

No. 43016 shutter, activated by a Lafayette 4301 1/16 Shutter Control. The control device

was interfaced with the microcomputer in a fashion such that a logic pulse triggered shutter

closure with a response time of less than 2.5 ms The generation of the appropriate logic

pulse was controlled by a 6502 assembler subroutine and was specified by a single

parameter modifiable at the beginning of each trial block. For trial blocks for which ambient

illumination was to be removed throughout the course of the movement, closure of the

shutter was triggered by the first change of the status of the stylus microswitch, that is

when subjects initiated their movement, and was reopened 2 seconds after initiation. For

conditions in which ambient illumination was available during the entire course of the

movement, the shutter remained open upon movement initiation.

Subjects were positioned relative to the display panel in a fashion similar to that for

Experiment 1. The starting platform was modified slightly to accommodate the stylus, but

remained in the same position relative to the subject's body axes. Control of stimulus

presentation and the timing of "critical" events was again controlled by the Apple IIe

microcomputer, and in all other respects the apparatus was identical to that used for

Experiment 1.

Page 124: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Eight pattern demonstration sheets were prepared, these comprised two example of

each of the four possible display sequences, aligned in a variety of orientations. Constituent

dots were clearly marked, and labelled according to the order in which they would normally

occur (Appendix 2). Acetate template sheets corresponding to each demonstration sheet and

containing the appropriate target at the centre of an "area of presumed correctness",

approximately ten times the diameter of the represented display dot, were prepared for the

purposes of comparing subject's responses with extrapolated target positions.

The experimental test materials were identical to those used in Experiment 1.

PROCEDURE

As a means of ensuring that subjects fully comprehended the nature of the test materials, all individuals, having been shown prototypical examples of each pattern, were

required to mark on the pattern demonstration sheets the position that they considered corresponded to the final dot in the sequence. These responses were then scored. Correct

responses were those for which the mark was positioned inside the superimposed area of correctness. No subjects made incorrect responses on any of the demonstration sequences.

Test sessions comprised of four blocks of 96 trials, two blocks with each responding hand, and for each hand one block in each visual condition. That is, on half of the blocks ambient illumination was removed upon movement initiation, on the other half it was not. The order of hand use and visual conditions was counterbalanced across subjects. Each test session was preceded by four blocks of 32 practice mals, each block

corresponding to one combination of hand and visual conditions.

Subjects were instructed to hold the stylus in a manner such that the Watsmart LED

was always upright and was not obscured from either camera. In all other respects the

procedure was identical to that for Experiment 1.

DATA REDUCTION

Following the experimental sessions, and for each trial,the two sets of "raw" 2-

dimensional linearized camera data were converted to three dimensional cartesian

coordinates, by Direct Linear Transforms, using a Northern Digital CONVERT program.

ASCII files of these three dimensional coordinates were then generated using a

DUMPDATA routine. The ASCII fdes were stored to disk for subsequent analysis. 110

Page 125: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

A custom designed program was employed to 'pick' from the ASCII files, the final

frame of data for each trial. This information then provided the x, y, and z coordinates of

the stylus and the x and z panel axis markers for the final frame of collection. This

information was saved to a single output file for each 96 trial block.

From the 3-dimensional coordinate data for all frames on each trial, instantaneous

vector velocity was computed by means of a two point central difference algorithm. The

velocity "curve" was smoothed with a 12.5 ms triangular window, and a custom "peak

picker"' program was used to establish the highest peak velocity, record its value and frame

reference. Instantaneous vector acceleration was computed, again by means of a two point

central difference algorithm and smoothed with a 12.5 ms triangular window. A custom

program was used to identify positive to negative, and negative to positive, crossings of the

zero "acceleration profile". from the time of highest instantaneous velocity to the

termination of the movement. A criterion 'windowing' filter was employed, such that

deviations from zero had to equal or exceed positive or negative 0.02 ms-2 to be registered as a "crossing". A fuller account of this procedure and a discussion of results is included in

Appendix C. The appropriate data concerning, the reference and stylus coordinates on the final

frame, total movement time as calculated from the Watsmart collection duration, peak

velocity, positive, negative and total number of crossings of the zero acceleration profile

were then merged with corresponding files containing the reaction time and movement time

data, obtained directly from the controlling micfocomputer, and information specifying the

board coordinates of the target position and presentation pattern on each trial. From this

information, simple calculations provided the x and z coordinates of the terminal position of

the stylus position relative to the target position. It was thus possible to calculate the

magnitude of "error" in both dimensions for each trial.

For each trial, data was available relating to; Reaction Time, Movement Time,

discrepancy between the stylus tip position and target position, along the x and z axes at

contact, Peak Instantaneous Vector Velocity reached during movement, the time taken to

reach Peak Velocity, and the number of zero crossings of the acceleration profde from the

time of Peak Velocity until the termination of the movement.

The calculation of Jerk profiles was precluded as it was a consistent characteristic of two

subjects, and an occasional characteristic of the remaining subjects, to make movements

which immediately after initiation involved a rotation which obscured the LED mounted

upon the stylus. Although this rotation generally lasted less than 50 ms it occurred with

sufficient frequency to make impossible the calculation of instantaneous Jerk during the

Page 126: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

period of greatest theoretical significance with respect to this variable, that is from movement initiation to peak velocity.

Page 127: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

11.3 RESULTS

MEDIAN REACI'ION TIMES

Median Reaction Time measures were obtained from each cell of the 128 unique

combinations of the six factors, each median value being derived from three trials. A repeated measures ANOVA was performed, the design was a 2 x 2 x 2 x 4 x 2 x 2 factorial

with Hand (right, left), Visual Condition (illuminated, non-illuminated), Visual Field (left,

right), Pattern (1,2,3, & 4), Relation to Midpoint (above, below) and Target Eccentricity

(outer, inner) as factors.The analysis revealed no main effects of statistical significance, nonetheless the trends may in themselves prove to be revealing.

TABLE 1 1.1 Median Reaction Time (ms) as a Function of Hand and Visual Field

Visual Field

Hand Left Right mean

Right 359.8 361.5 360.7

Left 347.9 351.1 349.5

mean 353.8 356.3 355.1

The left hand advantage, which although exhibited by six of the eight subjects and

evident across visual fields, did not reach statistical significance, F(l, 7) = 1.41, p > .05.

Similarly, there was no consistent effect of visual field, F(l, 7) = 0.76, p > .05. The

relationship of the means for each combination of these factors is graphically illustrated by

Figure 1 1.1 as follows:

Page 128: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL FIELD

Q RIGHTHAND LEFTHAND

-a

LEFT RIGHT

VISUAL FIELD

FIGURE 1 1.1 Median Reaction Times (ms) by Hand and Visual Field.

The apparent effect of Hand upon Reaction Time was also reproduced across the

Pattern factor. It is evident that that the left hand advantage was expressed across all levels

of Pattern.

TABLE 11.2 Median Reaction Time (ms) as a Function of Hand and Pattern.

Pattern

Hand 1 2 3 4

Right 359.8 357.8 362.2 362.9

Left 348.2 344.9 352.3 352.6

Page 129: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Once again the trends are well illustrated graphically, for example as follows:

HAND BY PATTERN

FIGURE 11.2 Median Reaction Times (ms) by Hand and Pattern.

370 -

360 - - z Y

What was apparently a consistent trend across display patterns, failed to reach

statistical significance, F(3,21) = 2.02, p > .05.

There was also no appreciable difference between median reaction times in the

illuminated (355.6 ms) and non-illuminated (354.6 ms) visual conditions, F(l, 7) = 0.02,

p > .05.

Right Hand Left Hand

A single higher order interaction reached statistical significance, this was the

interaction of illumination by field by midpoint by target eccentricity, F(l, 7) = 16.34, p < .005. The interaction accounted for considerably less than 1% of the total variance, and

was theoretically uninterpretable.

5

Page 130: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

MEDIAN MOVEMENT TIMES

In a fashion identical to that for Reaction Time, Movement Time measures were

obtained from the median of each cell of 128 unique combinations. A repeated measures

ANOVA was again performed, using a 2 x 2 x 2 x 4 x 2 x 2 factorial design, with Hand

(right, left), Visual condition (illuminated, non-illuminated), Visual field (left, right),

Pattern (1, 2,3, & 4), Relation to Midpoint (above, below) and Target Eccentricity (outer,

inner) as factors.

TABLE 11.3 Median Movement Time (ms) as a Function of Hand and Visual Field

Visual Field

Hand Left. Right mean

Right 421.7 409.8 415.7

Left 439.4 460.5 449.9

mean

There was a clear main effect upon Movement Time associated with the hand with

which the response was made, when using the right hand, subjects were consistently more

rapid, F(l, 7) = 15.13, p < 0.01. This effect was not expressed equally across the visual

fields in which the target position had been located, there was a clear, and statistically

significant, hand by visual field interaction, F(l, 7) = 14.16, p < 0.01. This relationship

between the respective means is clearly represented by figure 11.3:

Page 131: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL FIELD

VISUAL FIELD

470 - 460-

450 - h

2 440- V

2 430-

420 - 410 - 4 0 0 .

FIGURE 11.3 Median Movement Times (ms) by Hand and Visual Field.

/ RIGHTHAND LEFTHAND

1 I I d

Subjects completed movements more rapidly when moving their right hand into the

right visual field, and the left hand into the left visual field, than when maldng contralateral

movements, that is, when the right hand was moving toward targets located in the left

visual field and the left hand to targets in the right visual field.

LEFT RIGHT

Median Movement Time was also observed to vary considerably as a function of

the displayed pattern, F(3,21) = 11.18, p < 0.0001. Movements made in response to

pattern 3 were of longer median latency than those made to the other patterns, post hoc

analysis, in the form of pairwise comparison of the means using the Tukey (HSD)

procedure, indicated the presence of statistically significant pairwise differences between

the mean Median Movement Time to pattern 3 and all other Pattern conditions (Table

11.4b). This effect was expressed equivalently across both hands and visual fields, no two

or three interactions with pattern reached statistical significance. The relationship is

illustrated the pattern of means displayed in Table 11.4 and by Figure 11.4.

Page 132: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.4 Median Movement Time (ms) as a Function of Hand and Pattern.

Pattern

Hand 1 2 3 4

Right 379.6 402.5 480.2 400.6

Left 413.1 432.2 520.0 434.4

TABLE 11.4b Median Movement Time (ms) Differences amone Pattern Means

Page 133: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY PATTERN

* right hand + left hand

F'IGURE 11.4 Median Movement Times (ms) by Hand and Pattern.

The factor expressing the relationship of the target location to the midpoint of the target

display board, and consequentially the absolute distance from the starting position to the

target ("upper" targets were a greater distance from the starting position than "lower"

targets), was also associated with a statistically significant main effect, F(l, 7) = 10.85, p

< 0.05.

It is of little surprise that subjects took longer to complete movements covering greater

distance, those made to "upper" targets above the midpoint. This effect was also expressed

equally across both hands and both visual fields. There were no statistically significant

interactions with these factors.

Page 134: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.5 Median Movement Time (ms) as a Function of Hand and Relation to

Mid~oint..

Hand

Midpoint Left Right mean

Lower 437.7 402.7 420.2

mean 449.9 415.7 442.8

HAND BY MIDPOINT 470 -

LEFTHAND 4 RIGHTHAND

450

h

V

410

400 UPPER LOWER

MIDPOINT

FIGURE 11.5 Median Movement Times (ms) by Hand and Relation to Midpoint.

Importantly, there was no effect of Visual Condition upon movement time (mean

illuminated = 436.2 ms, mean non-illuminated = 429.5 ms), F(1, 7) = 0.06, p > 0.05.

Subjects completed the movements with equivalent latencies, irrespective of whether

ambient lighting was or was not available during the course of the movement.

1 2 0

Page 135: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Two higher order interactions were of statistical significance, a four way interaction of Visual Condition by Pattern by Midpoint by Target Eccentricity, F(3,21) = 5.05, p < 0.01, and the five way interaction of Hand by Visual Condition by Pattern by Midpoint by

Target Eccentricity, F(3,21) = 3.16, p < 0.05. Combined, these interactions accounted for a great deal less than 1% of the total variance and are theoretically uninterpretable.

Page 136: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

RADIAL, ERROR

Radial Error scores were subjected to a similar six way factorial, repeated

measures, analysis of variance (ANOVA), Hand by Visual Condition by Visual Field by Pattern by Relation to Midpoint by Target Eccentricity.

A main effect of statistical significance was obtained only for the factor of Visual Condition, F(l, 7) = 7.99, p c 0.05. This effect was consistent across hands and indeed all other factors. Individuals were more accurate, that is responses were terminated closer to the target position on an absolute scale, when ambient lighting was present throughout the duration of the movement.

TABLE 11.6 Radial Error tmm) as a Function of Hand and Visual Condition.

Hand

Visual Condition Right Left mean

Jlluminated 34.5 34.8 34.6

Non-illum 44.4 45.7 45 .O

mean 39.4 40.2 39.8

Page 137: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL CONDITION

FIGURE 1 1.6 Radial Error(mrn) by Hand and Visual Condition.

Significantly, there was no main effect associated with the hand making the response. The left and right hands were equally accurate, F(l, 7) = 0.32, p > 0.05. Similarly, there was an absence of main effects for Visual Field, F(l, 7) = 0.80, p > 0.05,

for Pattern, F(3,2 1) = 0.49, p > 0.05, and for all other factors. There was however, a single.higher order interaction which reached statistical

significance. This was the interaction of Hand by Visual Field by Midpoint, F(l, 7) = 11.22, p < 0.05). The relevant means are displayed in Table 11.7, the relationship is then graphically represented in Figure 11.7.

Page 138: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.7 Radial Error (mm) as a Function of Hand. Visual Field and Relation t~

MidDoint.

Hand

Right Right Left Left

- -

Field Left Right Left Right

Lower

upper

mean 40.9 38.0 42.0 38.5 '

- - -

HAND BY VISUAL FIELD BY MIDPOINT

R.H. (LV.F.) RH. (RV-F.) LJI. (LV.F.)

0 LJI. (R.V.F.)

37 ! I I i

LOWER UPPER

MIDPOINT

FIGURE 1 1.7 Radial Error(mm) by Hand, Visual Field and Relation to Midpoint

It is the case that for contralateral movements made by both hands, the magnitude of error

is greater for upper movements. Conversely, for ipsilateral left hand movements, that is,

Page 139: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

instances of left hand responses to targets located in the left visual field, accuracy increases when targets are above the midpoint, whereas for ipsilateral right hand responses, t h q is a weak trend toward increasing accuracy for lower movements.

Page 140: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

X CONSTANT ERROR

Mean Constant Error scores in the direction of the X axis of the target board were calculated for each of 128 cells for each subject. The mean scores were subjected to a six

way factorial analysis of variance (Hand by Visual Condition by Visual Field by Pattern by

Relation to Midpoint by Target Eccentricity). In this instance, positive error scores correspond to responses made to the right of

the target positions, in the right visual field and to the left of targets in the left visual field (from the subject's point of view), whilst negative values of course represent the reverse.

TABLE 11.8 X Constant Error (mm) as a Function of Hand. Visual Condition and Visual Field.

Hand

Right Right Left Left

VisualField Left Right mean Left Right mean

Illuminated - 19.8 -20.1 -19.9 -20.4 -18.2 -19.3

- -

mean -23.5 -16.7 -20.1 -24.4 -16.7 -20.5

As is quite evident, subjects exhibited a strong tendency to make movements which were

"undershoots" when made into either the left or right visual fields. Specifically, movements made into the right'visual field were generally terminated to the left of the target, and

movements made into the left field were to the right of the target position. This trend was

expressed across all combinations of the six factors. There was no apparent effect due to

the hand making the response, F(1,7) = 0.22, p > 0.05, for Visual Field, F (1,7) = 0.67,

p > 0.05, or for visual condition, F(1,7) = 0.72, p > 0.05, or interactions therein.

There were a number of higher order interactions however, all involving either the factor of

Target Eccentricity or Relation to Midpoint

Page 141: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.9 X Constant Error (mm) as a Function of Visual Field. Relation to Midyoint and Target Eccentricitv,

Visual Field

Left Left Right Right

Midpoint Lower Upper mean Lower upper hkan

Eccentricity

Inner

Outer - 18.6 -22.4 -20.5 - 12.3 -7.7 -10.0

mean -22.5 -25.4 -24.0 -17.7 -15.6 -16.7

Visual Field interacted with Relation to Midpoint, F(1,7) = 7.38, p < 0.05, and with

Target Eccentricity, F(1,7) = 15.07, p < 0.01. Illustrated most clearly by Figures 11.8 and 11.9, the first of these second order interactions reflects a tendency for movements made to upper targets in the right visual field to be associated with a smaller degree of undershooting than upper targets in the left visual field. By contrast, movements made to lower targets were associated with a smaller degree of undershooting when targets were presented to the left visual field

Page 142: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

VISUAL FIELD BY MIDPOINT

LV.F. R.V.F.

UPPER

RELATION TO MIDPOINT

FIGURE 11.8 X Constant Error (mm) by Visual Field and Relation to Midpoint.

Considering the interaction of Visual Field and Eccentricity, it seems that, while outer

targets were marginally less undershot, this trend was more clearly expressed for targets

presented in the right visual field.

VISUAL FIELD BY ECCENTRICITY

El L V F . -10 - R.V.F.

a w

4 U X

FIGURE 11.9 X Constant Error (mm) by Visual Field and Target Eccentricity.

Page 143: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

There was also a interaction involving these three factors, F(l, 7) = 6.23, p < 0.05, illustrated most clearly by Figure 11.8. This appears to indicate that the decreasing

magnitude of Constant Error associated with Outer targets in the right visual field, and described above, was predominant when the targets were also presented above the

midpoint.

VISUAL FIELD BY MIDPOINT BY ECCENTRICITY 0 -

LV.F. (LOWER) LV.F. (UPPER)

0 R.V.F. (LOWER) -10 - R.V.F. (UPPER)

a w

4 U X

I

INNER OUTER

ECCENTRICITY

FIGURE 11.10 X Constant Error (mm) by Visual Field, Relation to Midpoint and Target

Eccentricity.

There was a single, statistically significant main effect, that associated with the factor of Pattern, F(3,21) = 6.91, p < 0.005. The trends in the means across levels of Relation to

Midpoint , and of Target Eccentricity are represented in Table 1 1.10.

Page 144: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.10 X Constant Error (mm) as a Function of Pattern. Relation to Midpoint and Target Eccentricity,

Midpoint

Eccentricity Inner Outer mean Inner Outer mean

Pattern

mean -24.8 -15.5 -20.1 -26.0 -15.0 -20.5

The movements made in response to the presentation of pattern 2 were associated with a

slightly greater directional bias than those made to the other patterns. Pairwise, post hoc

comparisons of the means, using the Tukey (HSD) procedure, indicated the presence of

statistically signrficant pairwise differences between the mean X Constant Error for pattern

1 and that for pattem 2.(Table 11. lob). These trends are also evident in Figure 11.11.

Page 145: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11. lob X Constant Error (mm) Differences amonP Pattern Means,

PATTERN BY RELATION TO MIDPOINT

-26

0 1 2 3 4 5

PA'ITERN

FIGURE 1 1.1 1 X Constant Error (mm) by Pattern and Relation to Midpoint.

There were also present, higher order interactions associated with the factor of Pattern, with Relation to Midpoint, F(3,21) = 4.0, p < 0.05, reflecting a tendency for the degree of undershooting to targets specified by pattern 3 to be less when the targets were presented

below the midpoint, and with both Target Eccentricity and Relation to Midpoint, F(3,21) = 4.97, p < 0.01. Illustrated most clearly by Figure 11.12 below, this three way interaction

appears to indicate that the two way interaction of Visual Field and Relation to Midpoint is

accounted for primarily by responses to pattern 3 made to the less eccentric targets,

presented below the midpoint.

1 3 1

Page 146: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

PATTERN BY MIDPOINT' BY ECCENTRICITY /

0 7

FIGURE 11.12 X Constant Emr(mm) by Pattern, Relation to Midpoint and Target Eccentricity.

Page 147: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Z CONSTANT ERROR

Mean Constant Errur scores in the direction of the Z axis of the target board w& calculated in a fashion similar to that for X Constant Error. A repeated measures ANOVA was again performed, ths design being a 2 x 2 x 2 x 4 x 2 x 2 factorial with Hand (right,

left), Visual Condition (illuminated, non-illuminated), Visual Field (left, right), Pattern (1, 2,3,4), Relation to Midpoint (upper, lower) and Target Eccentricity (inner, outer) as factors. Positive error scores correspond to responses made to above the target position, whilst negative values represent errors made to below the target position.

TABLE 11.11 Z Constant E m (mm) as a Function of Hand and Visual Condition.

Hand

Visual Condition Right Left mean

mean -1.0 4.1

Casual inspection of the mean values presented in Table 11.1 1 belies the fact that there were in fact no statistically sigmficant main effects for Hand, F(1,7) = 3.79, p > 0.05, or for Visual Condition F(1,7) = 1.01, p > 0.05, or for an interaction thereof, F(1, 7) = 0.60, p > 0.05.

Page 148: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Although there wen no apparent main effects for Field, F(l, 7) = 0.14, p > 0.05, nor for Pattern, F(3,21) = 0.40, p > 0.05, there was a statistically si@cant Visual Field by Pattern interaction, F(3,21) = 6.58, p < 0.005, and a Hand by Visual Field by pattern interaction, F(3,21) = 3.85, p < 0.05.

As illustrated by Figure 11.13, movements made in response to Pattern 2, presented to the right visual field were, to a greater d e p , texminated above the target position.

TABLE 11.12 Z Constant E m h r n ) as a Function of Hand. Visual Field and Pattern,

Hand

Right Right Left Left

VisualField Left Right mean Left Right mean

-

mean -1.4 -0.6

Page 149: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

VISUAL FIELD BY PATTERN

n LEFI' 4 RIGHT

FIGURE 11.13 Z Constant Errortmm) by Visual Field and Pattern

It would appear that the Hand by Visual Field by Pattern interaction reflects an inordinate tendency for responses made by the left hand in response to pattern 2 to be completed above the target position when the pattern was presented to the right visual field. . ,

HAND BY VISUAL FIELD BY PATTERN

FIGURE 11.14 Z Constant Error (mm) Hand by Visual Field and Pattern.

lo-

5 - a V

4 5 0 -

rn R.H. (L.V.E) 4 R.H. (R.V.F.) E L.H. (L.V.F.) 4 L.H. (R.V.F.)

Page 150: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

There was obsmed a large main effect associated with the factor expressing the relationship of the target to the Midpoint, F(l, 7) = 64.28, p < 0.0001. This expresses a tendency to make responses which t h a t e above the target position when the target was below the midpoint, and to make responses erring below target position, when this position

is above the midpoint. This factor interacted &th only one other factor, that of Pattern, F(3,21) = 12.79,

p < 0.0001. As reflected in Figure 11.15, the tendency to undershoot upper targets and to overshoot lower targets is less visibly expressed in response to presentation of pattern 3.

The factor of Midpoint apparently did not interact with Target Eccentricity, F(l, 7) = 0.72, p > 0.05, and there was nothing resembling a statistically sigdicant main effect for Eccentricity.

TABLE 1 1.13 Z Constant Error (mm) as a Function of Pattern. and Relation to Miduoint

Midpoint

Pattern Lower U P P ~

mean

Page 151: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

MIDPOINT BY PATTERN

FIGURE 11.15 Z Constant Emr(mm) Pattem.by Relationship to Midpoint

Page 152: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

VARIABLE ERROR

In order to establish a meaningful measure of variable error, the cell structure for error values in the X direction was collapsed over the factors of Midpoint and Target Eccentricity, thus providing twelve values within each unique cell, from which a measure of vaxiability could be c a l c u l a ~ The Variable Esror scores thus obtained were subjected to a Four Way Repeated Measure ANOVA, the &sign being 2 x 2 x 2 x 4 factorial with Hand (left, right), Visual Condition (illuminated, non-illuminated), Visual Field (left, right) and Pattern (1,2,3, & 4) as factors.

TABLE 11.14 X Variable Error (mm) as a . .

Function of Hand. Visual Condmon and Visual Field.

Right Right Left Left

Visual Field Left Right mean Left Right mean mean

-

Visual Condition

Illuminated 19.1 17.1 18.1 17.2 17.6 17.4 17.8

Non-iUum 18.9 20.1 19.5 20.1 18.9 19.5 19.5

mean 19.0 18.6 18.6 18.2

Analysis of variance revealed no statistically significant main effects for Hand, (mean, right hand = 18.8 mm, left hand = 18.4 mm), F(1,7) = 0.68, p > 0.05, for Visual Condition, F(l, 7) = 2.48, p > 0.05, or for Visual Field, F(l, 7) = 0.45, p > 0.05. Indeed the trend as expressed through the mean values was toward greater variability for the Right

hand.

Page 153: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL CONDITION

RIGHTHAND LEFrHAND

fl ! I I d

ILLUMINATED NON-UUM

VISUAL CONDlTION

FIGURE 11.16 X Variable Error(rnm) Hand by Visual Condition.

TABLE 11.15 X Variable Error (rnm) as a Function of Visual Field and Pattern.

P a m Left Right mean

There was a statistically significant main effect for the Factor of Pattern, F(3,21) =

4.01, p < 0.05. A post hoc analysis involving a pairwise comparison of mean differences,

using the Tukey (HSD) procedure (Table 11.15b) revealed the presence of statistically

Page 154: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

signiscant pairwise differences between the Variable Enor in the X.direction for movements made in response to Pattern 3 and for responses made to all other Pattern presentations. TABLE 11.1% X Variable Enm (mm) Differences among Pattern Means.

**p < 0.01. I

In addition, there was revealed a Visual Field by Pattern interaction, F(3,21) =

7.45, p < 0.005. As illustrated by Figure 1 1.17,the increased variability associated with

Pattern 3 was more pronounced for movements made in response to target positions located in the left visual field.

VISUAL FIELD BY PATTERN

LElTFIELD RIGHT FIELD

FIGURE 1 1.17 X Variable Error (mm) Visual Field By Pattern.

Page 155: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

As for X Variable Error, the cell structure for error values in the Z direction was collapsed over the factors of Midpoint and Target Eccentricity, again providing twelve values within each unique cell. The Variable Error scores were subjected to a Four Way Repeated Measure ANOVA, again the design being 2 x 2 x 2 x 4 factorial with Hand (left, right), Visual Condition (illuminated, non-illuminated), Visual Field (left, right) and Pattern (1,2,3, & 4) as factors.

TABLE 11.16 Z Variable Error (rmn) as a Function of Hand. Visual Condition and Visual Field,

Hand

Right Right Left Left

- - - - -

Visual Field Left Right mean Left Right mean mean

Visual Condition

Illuminated 22.1 19.1 20.6 23.3 20.6 21.9 21.3

Non-illum 24.6 24.9 24.7 25.3 23.0 24.1 24.4

mean 23.3 22.0 24.3 21.8 22.8

The inferential analysis indicated the presence of a main effect for visual Condition, F(l, 7) = 6.64, p < 0.05, there was greater variability in the magnitude of error in the Z direction when movements were made in the absence of ambient lighting.

Similarly, there was greater variability for movements made in response to targets located in the left visual field, F(l, 7) = 6.10, p < 0.05.

There was, however, no apparent effect of the hand making the response (mean left hand = 22..7 mm, mean right hand = 23.0 mm), F(l, 7) = 0.36, p > 0.05. No higher interactions between these factorsattained statistical sigmficance. Some indication of the relative contributions of the factors of Hand and Visual Field is ~rovided by Figure 1 1.18

Page 156: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL FIELD

a ! I I d

LEFT RIGHT

VISUAL FIELD

FIGURE 1 1.18 Z Variable Error(rnrn) Hand by Visual Field.

The factor of Pattern was associated with a main effect of statistical significance, F(3,21) =

5.68, p < 0.01, pairwise post hoc analyses employing the Tukey (HSD) method revealed the presence of statistically significant pairwise differences in Z Variable Exror fur movements made following presentation of Pattern 1 and Variable Error associated with all

other patterns. Further, Z Variable Error when movements were in response to the presentation of Pattern 3 was appreciably lower, to a statistically significant degree, than

the Z Variable Error associated with Patterns 2 and 4 (Table 11.17b).

In addition, the interaction of Pattern and Visual Condition, as illustrated by Figure 11.19,

was of statistical sigruficance, F(3,21) = 3.65, p < 0.05. It appears that this may be

accounted for in terms of the greater variability associated with responses made to pattern 1, when ambient illumination was not present.

Page 157: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 1 1.17 Z Variable Error (mm) as a Function of Visual Condition and Pattern,

Visual Condition

Pattern Illuminated Non-illum mean

mean 21.3 24.4 22.8

TABLE 1 1.l7b Z Variable Enm (mm) Differences amonq Pattern Means..

Page 158: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

PATTERN BY VISUAL CONDITION

FIGURE 1 1.19 Z Variable Error (mm) Visual Condition by Pattern.

Page 159: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

VARIABIL,lTY IN TJ!E TIME TO PEAK VELOCITY,

In order to establish a legitimate measure of the variability in the time taken to'reach

peak velocity, the cell structure was collapsed ova the factors of Midpoint and Target Eccentricity, latencies fur individual trials thus provided twelve values within each unique

cell, from which a measure of the variability could be obtained. The Variability indices thus

calculated were subjected to a Four Way Repeated Measure ANOVA, the design being a 2 x 2 x 2 x 4 factorial with Hand (left, right), Visual Condition (illuminated, non-

illuminated), Visual Field (left, right) and Pattern (1,2,3, & 4) as factors.

The analysis failed to reveal the presence of a main effect fur either the factors of

Hand (mean right hand = 32.8 ms, mean left hand = 38.1 ms), F(l, 7) = 3.97, p > 0.05 or

for Visual Field, F(l, 7) = 0.1 1, p > 0.05. The factor of Visual Condition was, however,

associated with a main effect of statistical sigdicance, F(1,7) = 6.19, p c 0.05, (mean illuminated = 33.5 ms, mean non-illuminated = 37.4 ms). The relationship between the

mean values of variability obtained for all Hand-Visual Conditions is illustrated in Figure

11.20

HAND BY VISUAL CONDITION

30 ! I I I

illrrminated nan-ill1m.I

VISUAL CONDmON

FIGURE 11.20 Variabilitv in the Time to Peak Velocity as a Function of Hand and Visual

Condition,

Table 11.18 comprises the mean values of the variability for all combinations of the factors

of Visual Field and Hand. An interaction of these factors was observed, F(l, 7) = 7.87, p

< 0.05, representing a tendency toward increased variability for right handed movements 145

Page 160: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

made into the left visual field and for left handed movements made into the right visual

field. This trend is explicitly illustrated in Figure 1 1.21

TABLE 11.18 Variabilitv in the Time to Peak Velocitv as a Function of Hand and Visual

Field.

Hand

Visual Field Right Left

Left

Right 30.3 40.1

FIGURE Field.

HAND BY VISUAL FIELD

42 1

righthaad left hwd

-- I I

left right

VISUAL FIELD

11.21 Variability in the T i e to Peak Velocitv as a Function of Hand and Visual

Page 161: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Mean Peak Velocity measures were obtained b m each cell of the 128 unique. combinations of the six factors, each mean value being derived from three trials. As previously described, for other measures, a repeated measures ANOVA was performed, employing a 2 x 2 x 2 x 4 x 2 x 2 factorial design, with hand (right, left), visual condition (illuminated, non-illuminated), visual field (left, right), pattern (1,2,3, & 4), midpoint

(above, below) and eccentricity (outer, inner) as factors. The analysis revealed main effects of statistical significance for the factors of Hand,

F(1,7) = 24.55, p < 0.005, and for Field, F(1y 7) = 7.87, p < 0.05 and an interaction of these factors, F(1,7) = 75.44, p c 0.0001. Illustrated most clearly by Figure 11.22, and by the mean values contained in Table 11.20, the highest peak velocities were obtained for the respective hands when the response movements were being made into the ipsilateral visual field.

TAB= 11.19 Mean Peak Velocitv ( 4 s ) as a Function of Hand. Visual Condition and

- Visual Field,

Hand

Right Right Left Left

VisualField Left Right mean Left Right mean

Visual Condition

Illuminated 2.41 2.56 2.48 2.36 2.23 2.30

Non-illum 2.42 2.61 2.52 2.38 2.29 2.33

mean 2.41 2.59 2.50 2.37 2.26 2.32

Page 162: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TAB= 1 1.20 Mean Peak Velocitv h / s ) as a Function of Hand and Visual Field,

Hand

Visual Field Right Left mean

Left 2.4 1

Right 2.59

mean

HAND BY VISUAL FlELD

RIGHTHAND *- EITHAND

22 ! I I d

LEFT RIGm

VISUAL FIELD

FIGURE 11.22 Mean Peak Velocity (m/s) as a Function of Hand and Visual Field,

The factors of Visual Condition and Visual Field interacted in a fashion which

reached statistical significance at the 0.05 leveL As indicated by Figure 11.23 and by Table

1121, for movements made into the right visual field, mean peak velocities were greater

when ambient illumination was not present, F(1,7) = 7.13, p < 0.05.

Page 163: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.21 Mean Peak Velocitv ( 4 s ) as a Function of Visual Condition and Visual Field.

V i i Field

Visual Condition Left Right mean

Illuminated

VISUAL FIELD BY VISUAL CONDITION 2.46 1

LVF. R.V.F.

2 3 8 ! I I J

ILLUMINATED NON-UUM

VISUAL CONDITLON

FIGURE 1 1.23 Mean Peak Velocitv ( 4 s ) as a Function of Visual Condition and Visual

Field.

The effect of the Pattern factor was such that a statistically si@cant main effect

was obtained, F(3,21) = 9.29, p < 0.0005. A Tukey (H.S.D.) post hoc pairwise

analysis.of differences in the means produced three comparisons which were of statistical

s iwcance (Table 11.22b). Mean Peak Velocities achieved during reaches in response to

the presentation of Pattern 1 were appreciably higher than those achieved in response to all

other Patterns. There was observed an additional interaction of this factor with Target

Eccentricity, F(3,21) = 4.36, p < 0.05. From inspection of Figure 11.24 it would appear

Page 164: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

that this interaction reflects an elevated peak velocity for movements made to outer targets

in response to the presentation of pattem 4.

TABLE 11.22 Mean Peak Velocitv ( d s ) as a Function of Pattern and Target Eccentricitv.

Pattern

Eccentricity 1 2 3 4

Inner 2.52 2.4 1

Outer 2.50 2.4 1 2.32 2.43

TABLE 11.22b Mean Peak Velocitv (ds). Differences amow Pattern Means.

Page 165: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

PATTERN BY ECCENTRICl'l'Y

1 Q INNER

0 1 2 3 4 5

PATTERN

FIGURE 11.24 Mean Peak Velocitv (rnls) as a Function of Pattern and Target

Eccentricitv.

The Pattern factor also interacted with the Relation to the Midpoint, F(3,21) = 9.69, p < 0.0005. Indications obtained from the distribution of relevant means appear to

indicate that the mean peak velocities for movements made to above the midpoint were less

critically affected by variations apparently due to the presentation pattern. A main effect of

statistical ~ i ~ c a n c e was also observed for the factor of Midpoint, F(l, 7) = 61.f34, p < 0.0001. Clearly, higher mean peak velocities were obtained for movements made toward

targets located above the midpoint.

Page 166: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.23 Mean Peak Velocitv (mls) as a Function of Pattern and Relation to

-.

Pattern

Midpoint

Lower 2.42 2.28 2.14 2.3 1

PATTERNBYMIDPOINT

FIGURE 11.25 Mean Peak Velocitv (m/s) as a Function of Pattern and Relation to

Miduoint.

Page 167: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Two further, higher order, interactions were also present, illustrated by Table 11.24

and Table 11.25, and by Figure 11.26 and Figure 11.27 respectively. Hand interacted with

Visual Field and Target Eccentricity, F(l, 7) = 28.46, p < 0.005, in a fashion which

indicates that, for the right hand, movements made into the right visual field were accompanied by mean peak velocities which increased with target eccentricities, whilst for

movements made toward the left visual field, peak velocity decreased with target

eccentricity. For the left hand, the pattern was reversed, peak velocity increased with

eccentricity for movements made toward the left visual field and decreased with increasing

eccentricity for movements made to targets in the right visual field. Or more succinctly, for ipsilateral movements, peak velocity increased with eccentricity, whilst for contralateral movements, peak velocity decreased with eccentricity. This illustrates once again the pervasive nature of what are apparently spatial compatibility effects.

TABLE 11.24 Mean Peak Velocity (m/s) as a Function of Hand. Visual Field and Tarrret

Eccentricity.

Visual Field Right Left

Left Inner

Left Outer

Right Inner 2.54

Right Outer 2.64

Page 168: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL FIELD BY ECCENTRICITY

u - I

INNER

FIGURE 1126 Mean Peak Velocitv (mls) as a Function of Hand. Visual Field and Tarpet

E-

The second three way interaction was that of Hand by Visual Condition by Pattern,

F(3,21) = 3.34, p < 0.05. As illustrated by Figure 1 1.27, this interaction was somewhat

complex. There is some reason to suggest that the more general, though weak, trend for the

mean peak velocity of right and left hand movements to be greater when ambient

illumination was not present, was to some extent reversed for the right hand only when

responses were made to pattem 3. One can only assume that the interaction had some

consistency which is not reflected by initial examination of the means.

Page 169: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 11.25 Mean Peak Velocity (mls) as a Function of Hand. Visual Condition and

Pattern.

Hand

Right ,' Right Left Left

Visual Condition Illllminated Non-illum Illuminated Non-illum

Pattern

4 2.48 2.5 1 2.27 2.33

mean 2.48 2.52 2.30 2.33

Page 170: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY VISUAL CONDlTION BY PAITERN

FIGURE 11.27 Mean Peak Velocitv (1x11s) as a Function of Hand. Visual Condition and

Pattern.

Page 171: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

1 1.4 DISCUSSION One of the primary considerations of this study was the examination of the potential

differences which may exist between the preparation for, and the regulation of, movements

made by the preferred and non-preferred hands. In all cases, in experiments 1 and 2, subject's preferred hand was their right. Reaction Time may be considered as being some index of the time required for movement preparation , though at this stage it is important

that it should be clearly distinguished from accounts of Reaction Time as the time for

movement "programming". In this experiment, as in Experiment 1, there was no statistically significant main effect for reaction time associated with the hand making the response, although in both cases, the mean latency to initiate responses was lower for the

left hand in six of eight subjects. The magnitude of this mean difference was approximately 10 milliseconds in each experiment, yet was obviously expressed with an inconsistency

such that the attribution of any functional significance to this difference must be approached with considerable caution. It is tempting to speculate that for movements which were

themselves matially complex, as was seemingly the case for the movements made in these

experiments, the right hemisphere would be involved in the preparation for action to a

greater extent than for less spatially complex movements, which perhaps did not involve

this progression into extrapersonal space. Certainly, in simple or choice reaction time studies, in which the spatial topology of the response movement is considerably diminished, a right hand advantage is more generally observed (e.g., Anzola, Bertoloni, Buchtel & Rizzolatti, 1977), while Kimura and her associates have argued, on the basis of

clinical evidence (e.g., Kirnura, 1974; 1977; 1979; Lomas & Kimura, 1976; Lomas, 1980)

that the left hemisphere is superior for "movement programming", an advantage which is

ostensibly reflected in the pattern of impairments for tasks which emphasise

preprogramming". The trend towards a left hand advantage in the present experiment may

reflect the presumed shift toward greater right hemisphere involvement which is thought to

accompany an increasing relative spatial complexity of the response movement.

Much greater between hand differences were exhibited, in this experiment, in terms

of measures which are assumed to reflect other facets of movement regulation. Responses

initiated by the right hand were completed more rapidly than those made by the left hand.

This effect may usefully be compared with trend for Mean Peak Velocity which is the

inverse of that for Movement Time, it is not unexpected that the larger peak velocities

exhibited by the right hand were associated with shorter movement times, though this was

not assessed on an individual trial basis. If the Mean Peak Velocity may indeed be regarded

as some indicator of the applied impulse, it would appear that greater force was generated

Page 172: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

by the preferred hand, a result which would not be unanticipated, or at least that an equivalent force was applied for a longer period.

In view of the claim made by Annett, Annett, Hudson and Turner (1979) that the

non-preferred hand is more variable in its output of force, the relative variability in the time

required to reach peak velocity may be seen as a preliminary means of testing this

assumption. Although there w& a relatively consistent tendency for movements made by

the left hand to be associated with greater variability in the time to peak velocity, this apparent effect failed to meet the criterion adopted for defining statistical sigdicance.

Obviously a measure of Jerk, had this been available, would have been a more direct means

of assessing the variability in applied force. Variable Error has been considered a measure of the accuracy with which a pre-

existing motor program is executed (e.g., Guiard, Diaz & Beaubaton, 1983). Although one may find strong cause to reject this interpretation, there may still be some utility in simply taking Variable Error as a pointer as to the fluctuation of the terminal locations of

movements, to "equivalent" targets over a course of trials. In this respect there was no

appreciable difference between the hands for variability in either the X or Z directions. One might again speculate that, for spatially complex movements, the manifestations of a presumed greater right hemisphere involvement in &ding with an "abstraction of space"

are not confined to events temporally preceding the initiation of movement. Therefore, for movements of this nature one would perhaps not expect a left hand advantage for a measure of the accuracy, or at least variation in accuracy of execution.

Radial Error may be regarded as the most comprehensive indicator of the accuracy with which subjects completed their responses, providing, as it does, information on the

absolute distance between the position of the phantom target and the terminal location of the movement. In more concrete terms, it is a demonstration of how successful the subject was in accomplishing his action goal, albeit a goal which was &fined by the experimenter.

Overall, individuals were remarkably accurate, bearing in mind the fact that the target

position was never actually displayed. Movements were completed a mean distance of

approximately 40 mm from the target. There was however no advantage for the preferred

right hand. Although there are problems associated with the interpretation of any non-effect

in this context, this trend is particularly noteworthy as a preferzed hand advantage, in turns

of overall accuracy, has been widely anticipated in literature which to date has been

insensitive to the influence of any more than a limited set of specific task demands. As will

be outlined in the General Discussion, experimental identification with the null hypothesis

is not beyond the scope of current research in "Motor Control". It does not appear that the

measure of Radial Error was insensitive as such, there was detected a main effect 158

Page 173: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

associated with visual conditions which will be discussed in greater detail below. Rather, it simply appeared that responses made the preferred and non-preferred hands were ,

equivalent in teminal accuracy. In view of the global charactefistics of this pointing task, a progression to locate a point in space, it is again possible to hazard- the explanation that the

usual increased left hemisphere activity which is contiguous with the regulation of simple movements is for complex movements, on a temporal basis, accompanied by, and on a

quasiphysical basis, transacts with an increased right hemisphere involvement. This

transaction to be expressed in measures sensitive to the regulation of the ongoing

movement. Rather than considering Constant Error as indicative of the accuracy of "central

programming" (Guiard et al., 1983), one should perhaps maintain rather less grandiose expectations and regard this measure in its primary form, as merely the directional bias of a series of movements. In this experiment there was essentially no evidence of a difference

between the responding hands in terms of Constant Error in the X direction. Similarly, for

measures of Z Constant Error, although it appeared that right hand movements tended to

slightly undershoot target positions and left hand movements to more appreciably overshoot (in this case terminate above targets), this effect had little consistency.

Clearly a central consideration in this investigation was the effect of, what was presumed to be, an imposed manipulation of spatial complexity. As discussed with respect to Experiment 1, it was felt that the desired manipulation might only be achieved by giving

subjects a prior conscious awareness of the precise nature of the pattern sequences. The

pre-experimental test sessions with example displays indicated that apprehension of the

sequences could be achieved most rapidly. Thus there may be some assurance that

individuals were able to appreciate the correspondence between a pattern and the

appropriate target location. Post practice session and post experimental debrieiings at least indicated that subjects experienced some confidence as to their ability to extrapolate to target

locations. Reaction Time measures failed to indicate the presence of any appreciable

differences between patterns, though ktt3re~tinf& a trend across both responding hands

was for responses to the presentation of Pattern 2 to be initiated more rapidly than, for

example those to what was supposedly the more "simple" pattern 1. The magnitudes of

these differences in the means were small and statistically not sigdicant. There was no

evidence of interaction between the factor of Pattern and either the hand making the

response movement or the visual field in which the sequence was presented.

The absence of an interaction with Visual Field is particularly important. When the

task of interest requires a relatively uncomplicated manual response, reaction time measures 159

Page 174: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

may be regarded as reasonably good indicators of the processing charactastics of the

cerebral hemisphere which first receives the stimulus information, in this case the ,

hemisphere contralateral to the visual field in which the pattern was displayed. In these

circumstances one might anticipate that a right hemisphere advantage, in terms of the

rapidity with which spatial relationships are "appreciated", would be manifested as a left

visual field superiority, and extending this reasoning expect an interaction with Pattern.

However, as Bashore (1981) points out, the characteristics of reaction time indices may

vary considerably as a function of the type of movement required. In these current

experiments, it is likely that the highly complex nature of the movements was such that the

idiosyncratic stimulus processing characteristics of the receiving hemispheres were overshadowed to a large extent. Certainly, the reaction time latencies obtained in both

Experiment 1 and 2 (404 and 355 ms, respectively) are appreciably higher than those obtained in the simple reaction time studies reviewed by Bashore (1981), which are almost

universally below 300 ms. As a choice element is introduced, in the current experiments through the use of a number of target positions and indeed a variety of patterns, the likely

contribution of various factors becomes even more complex, as Bashore (1981) comments: The result is that variables known not to influence simple reactions do alter the time required to make choice decisions. The cerebral mechanisms responsible for producing these effects are unknown (p. 374).

Another possibility exists, that the nature of the pattern was such that, containing elements

which were both spatial in nature and encapsulating a progression which was sequential, there may have been inherent characteristics which favoured the processing "functionalities" of each hemisphere. Whilst continuing to maintain that it is not plausible that one hemisphere is uniquely specialized for the sequential processing of information

(see Chapter 3), it does appear to be the case that the displays used in these experiments may comprise aspects which involve the partial involvement of both hemispheres. Certainly

it did appear that most of the effects associated with the Pattern manipulation were

expressed symmetrically.

In section 11.1 it was suggested that a subject of interest was an enquiry as to

whether any effects associated with the characteristics of the visual information speclfylng

target position recurred throughout the course of the movement. This recursion, if present

was, it was hypothesized, to be expressed particularly in terms of kinematic indices. This

potential recursion was in contrast to the view, expressed by Fisk and Goodale (1985), that

the influence of spatial localization was confined to "neural systems" prior to those

concerned with motor output. In this enterprise it is worth reemphasizing that the pattern

presentation was terminated some time prior to the initiation of movement, there was on

average a delay of over 200 ms from sequence offset to response initiation. 160

Page 175: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

A systematic variation in movement time was associated with the presentation

pattern, the required to complete responses to targets specified by Pattern 3 was appreciably greater than when indicated by any othcr pattem. FranLs (note 3) has speculated that some

degree of "tracking" may be occurring. This seems unlikely as the stimulus is never actually present during the movement itself. Also, if some form of imagery is involved, as a substrate for tracking, one would anticipate that a positive relationship would exist

between movement time and the magnitude of the distance between successive presentation

points (c.f., Cooper & Shepard, 1973). If this were the case, the movement times

associated with Pattem 4 would presumably be longer than those for Pattern 3, clearly this

was not the case.

Higher initial impulses, such as those which, it is inferred, accompanied right hand

movements have been associated with greater variability and consequently reduced terminal accuracy (Schmidt, Zelaznik, Hawkins, Franks & Quinn, 1979), yet in these instance, the left hand was slightly, if not sigmficantly, mare variable in terms of the time to reach peak velocity, and no more variable in measures of tenninal accuracy as expressed by X and Z

Variable Error. It may be the movement, in its time course to "peak velocity", although not in itself unmodified or ballistic, may bring the right hand closer to the target position, in

spite of the greater initial impulse. Indeed this possibility has been discussed by Todor and

Cisneros (1985). One might further suggest that the variation in accuracy as a function of

initial force production observed by Schmidt et al. (1979) in response to increased accuracy

demands, is qualitatively different from the relationship between initial impulse and

variability which appears to differentiate the hands. Following this reasoning, movements

made in response to the presentation of Pattern 3, perhaps arising indirectly from some

"ambiguity" associated with the nature of the pattern, may result in motion which in the

initial phases is further from the target location. This may be regarded as purely speculative at present and a topic for further investigation.

As Prablanc, Eschallier, Komallis & Jeannerod, 1979 have demonstrated, the relationship described by Fitts Law is maintained in the absence of visual feedback. Carlton (1979) has suggested that kinematic analysis of movement profiles supports a "discrete

feedback interpretation" of this relationship. Clearly for the movements presently being

discussed, discrete modifications were not necessarily subject to the direct influence of

visual information. Prablanc, Pelisson & Goodale (1986) have commented that 'open loop' movements (open loop with respect to visual feedback about the relative positions of the target and the moving limb) are far from being uncorrected or ballistic. Indeed, the prime effect of target duration on pointing accuracy suggests that visual information about target location is somehow used to control the movement during its execution.

Page 176: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

To this it might be added that "open loop" movements are far from being

"uncorrected", or at least unmoditi.ed, in the absence of concurrent visual information

relating to the moving limb and the target, aithough some information initially derived

from the optic array is used to regulate the movement during execution. One must conclude

that some affardance as to the position of a "target" in extrapersonal space is provided by a change in the optic array ova the &tially static eye, even when the position of the target

itself is never explicitly defined. The mechanisms through which this may occur are discussed in greater detail below.

There was no effect of Pattern upon the absolute accuracy of the response as

expressed by Radial Error, though there was an effect of Pattern associated with X Constant Emr. Interestingly, movements made in response to the presentation of Pattern 1 exhibited less variability of terminal error in the X direction, yet appreciably more variation

for errors in the Z direction. In the latter case, the Variable Error of responses made to Pattern 1 was sigmficantly larger than for all other patterns and might conceivably represent

a sensitivity to occasions on which the direction of the sequence, the temporal progression,

was misapprehended. Subject's comments during practice trials indicated that there was

some initial ambiguity associated with Pattern 1 in this respect. However, it is p e g that

this potential equivocality was not also expressed in terms of X Variable Error, as

misapprehension of the pattern, and a resultant response at the "wrong end" of the pattern

represents error in both directions. The magnitu& of the peak velocity achieved during the course of the movement

was directly influenced by the nature of the pattern which had defined the target, Responses

to Pattern 1 were accompanied by peak velocities higher than those for all other patterns.

The lowest peak velocities were observed for responses to Pattern 3. As for considerations of the hand making the response, there appears to be no

straightfmard relationship which exists between, the distribution of initial impulses as

reflected by Peak Velocity and the variability of terminal location as reflected by both

Variable Emr measures. The trend in terms of peak velocities was not unambiguously

related to Variable Emr, although Z Variable Error (figure 11.19) more closely resembled the trend in Peak Velocities (figure 11.24). This somewhat confusing picture serves to emphasis the caution which should be exercised in attaching impo~ance to the measures of

Constant and Variable Enw= The axes utilized were defined with respect to the display board and are thus somewhat arbitrarily imposed upon the subject. There is no direct

reference to whole body or joint axes, other than in terms of alignment with the fixation

point. The body segments may be potentially described with respect to a Cartesian

Page 177: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Coordinate system, yet they are certainly not organized on this basis (c.f., Turvey &

Carello, 1986). Perhaps the most striking characteristics of the data collected were the indications

that visual infomation related to the motion of the responding hand contributed

signifcantly to the terminal accuracy of the movement, as expressed by measures of Radial

Error. It should be recalled that visual infomation of the position of the target was never

explicitly made available, and the visual stimuli comprised implicit indications of the target

location were never available during the course of the movement. As a consequence, at no

stage was there present, visual information regarding the relative positions of the target and the responding hand.

Vision of the responding hand was obviously useful for the regulation of movement toward a target which was never explicitly defined in equivalent terms. It was never possible, for example, for individuals to direct an eye saccade towards the actual position of the target in space. Indeed it is a topic of enquiry as to the role assumed by the terminal position of the first saccade following sequence presentation. Fisk and Goodale (1985)

have discussed that, in circumstances in which targets are presented only briefly and are extinguished prior to movement initiation, the point fixated by the eyes may serve as the

target for the subsequent limb movement. These authors observed a positive correlation

between the final positions of the eye and the limb movement, again suggesting that the

area of space fixated by the eyes may have constituted the best available indicator of target location. It was in the present circumstances impossible to establish whether eye

movements were directed to the position of the final point of light projected, to some other

element of the sequence or to some related point in extrapersonal space which had not been illuminated. There was no variation in terminal accuracy associated with the pattern which

had been displayed. This perhaps may be taken as circumstantial evidence that the final dot

presented was not taken as the best indicatur of the target, the final displayed point for

Pattern 1 was closer to the target than, for example, the final displayed point of Pattern 4,

though there were no accompanying differences in accuracy. The extK'aI't2~al signal

associated with eye movements may have been equivalent across all patterns. Certainly if

an eye movement was made to an area of space rather than to a specific point of the target

display this may well have been the case. If extraretinal signals were used as the

predominant basis for the approximate localization of target position, the non-specifi.city of

this signal across all Pattern presentations would be well carrelated with the equivalence in

tenninal position. Although it has been observed that extra-retinal signals represent a rather

impoverished source of information when other cues are available (Prablanc et al., 1986),

in the absence of accurate foveal infoxmation as to the position of the target, these imprecise 163

Page 178: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

extra-retinal signals must represent the best basis on which the subject may proceed. One

might enquire whether a saccade to an ill defined region of space, providing some foxm of extra-retinal signal provides more potent information than the flow of information over the

static eye, a situation which occurs during stimulus prsmtation. Obviously further

research, in which eye movements following presentation were not permitted would provide some resolution of issue.

The directional biases of the pointing movements may themselves be directly

influenced by the nature of the, initially contiguous, eye movements,and as such may

provide some indication of the relative contributions of extra-retinal and optic-flow related

signals. As touched upon in Chapter 7, one of the most consistent characteristics of the oculu-motor system is for initial saccades to undershoot the target. Conventionally, when

target information is C O I I M U O ~ ~ ~ ~ available, a second "corrective" saccade of smaller magnitude brings the target into foveal vision. This has a practical utility, for eye movements, as for limb movements, it is advantageous to initially undershoot than

overshoot, movements involving reversals being at least more time consuming. In this

experiment, the subject was never afforded the opportunity to make a second corrective saccade, initial saccades were not only likely to have been somewhat inaccurate, they were also likely to have been undershoots. If extra-retinal information pertaining to the initial

saccade was used as the primary estimate of target position, it is likely that the resultant

movements would also exhibit some degree of undershootingHowever as there was some evidence of the presence of interactions for Constant Error measures, particularly involving

the factor of Midpoint, it may be possible that biomechanical factm or at least factors

associated with the execution of the limb movements account, in part, for the tendency to

undershoot. It may have been that the biomechanical system constraints were such that

undershoots were more likely, though whilst there was a Hand by Visual Field by

Midpoint interaction for Radial Error (the possible mechanisms underlying which are discussed below) there was no consistent directional bias which would lead one to

emphasise the exigency of such constraints. Importantly, Fisk and Goodale (1985) observed that the correlation of the terminal positions of eye and limb movements varied

significantly as a function of target exposure duration. Then was a stronger relationship

between the respective tenninal accuracies when a brief, 100 ms exposure condition was

used, in which the only information related to target position was apparently that provided

by the extra-retinal information. In the longer duration condition, subjects were able to

locate the target in foveal vision and obtain indications as to the relative positions of the

target and the responding had duxing the latter phase of the movement, therefore the

position of the eye on completion of the first saccade was likely to have contributed 164

Page 179: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

proportionately less to the regulation of the movement. Although in the present experiment

it would appear impossible to disentangle the possible effects of biomechanical factors from

those relating to extraretinal signals in terms of influencing terminal accuracy, and therefore

becomes difficult to assess the relative contributions of retinal (in the form of changes in the

optic flow field over the static eye) information and extra-retinal information, to the initial

establishment of general target location, it does appear reasonable to assume that extra-

retinal information accompanying the first saccadic eye movement was particularly

important. To consider again the issues raised in Chapter 7, it may be a normal characteristic of

normal reachindpointing movements to exhibit "ongoing corrections" subserved by motion

related, non-visual information and visual target information which require very little time

(Prablanc, Pelisson & Goodale, 1986). One should note of course, the similarities and

differences between the present experiment, and the Pelisson, Prablanc, Goodale and

Jeannerod (1986) study in which "pseudocontinuous" modifications of the movement

trajectory were made in the absence of visual information of the relative positions of the

target and the limb. In the latter study, modifications of the movement trajectory were

necessary to accommodate perturbations of the target. There was no visual information

available as to the position of the moving limb. The authors argue, on the basis of the Prablanc et al. (1986) results, that:

a dynamic control system existed in which extra-visual information about the position of the moving limb is compared with visual information about the position of the target @. 303).

In this experiment, however, it was the case that there were improvements in

terminal accuracy, potentially arising from non-discrete, or at least non time consuming,

modifications of the movement trajectory, when information about the position of the

moving limb was available. Information relating to the position of the target could, during

the course of the movement, only have been extra-visual, and was probably initially extra-

retinal. Paillard (1982) has emphasized that movement cues, quite possibly those obtained

in the periphery as vision of ones body segments, are closely associated with motion

relative to the visual axis previously established by foveal grasp of the target. The results of

the present study would appear entirely consistent with this synopsis, in that, both the visual axis and the target position were probably established by foveal gasp, and in this

case foveal vision could be considered as relatively unimportant in the regulation of

movements for which a terminal comparison of target and hand positions, ostensibly

subscrved by foveal vision, could never occur.

The results of this experiment also provided confirmation of the highly pervasive

nature of what might be termed spatial compatibility effects. It is the nature of these effects I . 165

Page 180: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

to which attention will now be devoted. In line with the results obtained from Experiment

1, there were no indications of Visual Field by Hand interactions for measures of Reaction Time. Whilst, as outline above, there is reason to believe that the patterns of movement

initiation latencies for complex pointing or reaching movements will differ appreciably from those for simple or choice reaction time paradigms, it is puzzling that there was no

convergence with the results obtained by Fisk and Goodale (1985) who used similar

reaching tasks and elicited spatial compatibility effects for reaction time measures.

Nevertheless what are apparently consistent effects of this nature appeared to transcend the

most simple behavioural description of the pointing movements. For the measure of

Movement Time, there was an appreciable Hand by Visual Field interaction. For both

hands, contralateral movements consumed more time than the ipsilateral equivalents. Although there was no expression of a similar effect upon the terminal accuracy of

the movements, there was for Radial Enor a higher order interaction of Hand by Visual

Field by Midpoint. This trend will be discussed in greater detail below, suffice to say at

present, contralateral movements for both hands were associated with greater error when

made to above the midpoint, whereas for ipsilateral responses there was some divergence

of the hands. Left hand responses to the left visual field were more accurate when to upper

targets, whereas, right hand responses were more accurate to lower targets presented in the right visual field.

There was no evidence of a Hand by Visual Field interaction in terms of the tendency to undershoot targets as expressed by X Constant Error, nor any equivalent interaction for Z Constant Error, nor for either measure of terminal variability. In terms of the variability in the time to achieve peak velocity, there was a statistically significant

interaction of Hand and Visual Field, contralateral movements were associated with greater

variability than the ipsilateral equivalents. If this measure, as has been suggested, may be regarded as some index of the initial impulse, there may be some reason for considering

that there was greater variability in the initial production of force for contralateral movements. One should also be aware that this measure may also be sensitive to the time

course over which the impulse was described. It may be that electromyographical monitoring of muscular activity during these movements may serve as a suitable basis for

comparison of the initiation of contralateral and ipsilateral movements. The Hand by Visual

Field interaction in terms of the Mean Peak Velocity achieved during the movement

suggested that contralateral movements were associated with lower peak velocities and

potentially lower initial impulses. These indices may collectively suggest that the reasons

for the increased movement times for contralateral movements were not due to

biomechanical factors exerting an influence while the movement was "unfolding". 1 6 6

Page 181: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Although the distance moved by the tip of the stylus may have been the same for ipsilateral

and contralateral movements, the displacements of the centre of mass of the responding

limb may not have been equivalent. The inertial characteristics of contralateral movements

are unlikely to be the same as inertial characteristics for ipsilateral movements. Although

biomechanical factors cannot be completely excluded, there are additional reasons to believe

that these influences do not form the primary basis of spatial compatibility effects.

Fisk and Goodale (1985) devoted particular attention to examination of whether the

kinematics of limb movements, and in particular the differences between ipsilateral and

contralateral reaches could be accounted for by differential biomechanical constraints or

patterns of muscular activation. The monitoring of eye movements revealed that, as with

limb movements, saccades were initiated more slowly when they were accompanying

contralateral reaches. Perhaps more importantly, the scaling of movement times observed

for limb movements was reproduced for eye movements, even though it was the case that

for contralateral and ipsilateral limb movements into for example the right visual field, the

eye movements required to fixate the target were identical in either case. Although the eye

movements were completed more rapidly than limb movements, the eyes having smaller

inertia to overcome, they were initiated equivalently. In concrete terms, the reaction times

were highly correlated Fisk and Goodale (1985) argue that the temporal synchrony of the

two motor systems must be accounted for as a "common integration of motor

programming .... at higher levels in the central nervous system".

These authors also suggest that it is unlikely that the pattern of response latencies

and velocities profiles was influenced by purely mechanical constraints, as for contralateral

reaches, peak velocity was achieved some time before the hand crossed the body midline,

movements at this point were topologically still ipsilateral. They argue that "braking" due to

antagonist activity in contralateral reaches was a contributing factor only in the final stages

of the movement. In this sense the claim that differences in patterns of muscular activation

operating in each case are not the basis of the observed differences, one must distinguish

between the muscular activity associated with the initial impulse, presumably agonist firing,

and the subsequent activity which contributes to what appears to be the regulated nature of

the trajectory.

In view of the clear differences between ipsilateral and contralateral reaches, in

terms of the peak velocity achieved and the variation in the time required to reach that peak

velocity, and by implication the initial impulse, and associatively the initial pattern of

muscular activity, one must conclude that spatial compatibility effects may be at least

partially reflected in the characteristics of initial muscular activation. There is other

circumstantial evidence which appears to justify an exclusion of biomechanical factors in 167

Page 182: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

favour of some explanation in terms of the neural activity associated with the preparation

and execution of movement. Electrophysiological data collected by Georgeopoulos, Kalaska and Massey (1981) has been taken to suggest that the activity of single neurons in the motor cortex is highly dated to the direction of an associated hand movement.

Movements in eight possible directions were considered, and it was noted that motor

neurons displayed "directional specificity", the highest level of activity in a particular motor

neuron was associated with movement in one direction. Signrficantly, the level of discharge

was generally greatest for ipsilateral movements made foxward into space and outward

from the body axis. Finally one must also consider that in studies examining spatial

compatibility effects and employing a choice reaction time paradigm (e.g., Anzola et al.,

1977), the response movements are such that they are essentially uninfluenced by biomechanical constraints. Whilst it is the case that reaction time in these instances must be

considered in part a reaction time/movement time composite, spatial compatibility effects

are clearly expressed.

It may be concluded that it is a strongly exhibited characteristic of the "motor

system" to exhibit differences, both qualitative and quantitative, between movements which

cross the visuallbody axis and are completed in contralateral space, and those which

proceed entirely ipsilaterally. However, the underlying mechanisms must still be regarded

as unclear, although it does appear that the phenomenon must be considered "higher order"

rather than as arising as a consequence of biomechanical constraints. Ladavas (1987) has demonstrated that spatial compatibility effects may exist in the

absence of any overt correspondence between the spatial properties of the stimulus and the

required response. Generally the right hand exhibited a greater compatibility with "upper"

targets and the non-dominant left hand responded more quickly to lower visual stimuli. Although the experiments described by Ladavas were conducted within the context of a

choice reaction time paradigm, it was of some interest to examine whether these presumed

relationships would be maintained, or of any other consistent correspondences would apply

in situations in which the response act was a more complex movement involving a

progression through space. Once again it is the nature of interactions which are of primary

interest. Main effects associated with factors such as the relationship of the target to the midpoint are themselves of little intrinsic interest. If these effects are present and are expressed in a way similar to the more conventional spatial compatibility effects, these

correspondences are likely to be consistently revealed by a number of dependent measures,

themselves assumed to be sensitive to varying but related aspects of the preparation for and

execution of movement.

Page 183: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Reaction Time measures failed to reveal what, on the basis of the Ladavas work,

might have been an anticipated Hand by Relation to Midpoint interaction. More generally

Reaction Time measures were not associated with main effects or with interactions of

statistical significance, other than a theoretically uninterpretable four way interaction. It is conceivable that the use of m a a n values failed to compensate for problems related to the high variability associated with reaction time measures. Each of 128 cell values for a given subject was composed of the median of three values, this may not have been sufficient to

compensate for the anticipated skewness of within cell distributions.

Indications from measures of Median Movement Time were similarly unrevealing.

Although, as previously discussed, there was an anticipated main effect associated with the

relation of the target to the midpoint, there was no apparent interaction with the responding

hand It was of some interest to note that, in terms of X Constant Error, movements made to targets located above the midpoint were associated with a lesser degree of undershooting when these targets were also in the right visual field, the reverse holding true for lower

targets. However, there was again no interaction with the responding hand This bias was

also exhibited most clearly for movements made to outer targets, Visual Field, Eccentricity and Relation to Midpoint interacted, indicating that the reduced degree of undershooting to

outer targets was greater when these were also upper targets. None of these trends appear

to bear directly on the spatial compatibility effects noted by Ladavas (1987). Similarly, Z

Constant Error scores and Radial Error provided no indications of particular interest in this

respect. Given that the measures of Variable Error and the Variability in the Time to Peak

Velocity were collapsed over the factors of Midpoint and Target Eccentricity, they will not

be considered further. Likewise the Mean Peak Velocity provided no illumination of this

supposed phenomena.

It is necessary to exercise some caution. In the absence of any a priori outline of

this presumed effect, and with a coexisting ambiguity as to the mechanisms underlying this

phenomena, there could be no specification of the means and measures through which it

would be expressed. As such there is some reason to place limited trust in the results of

"data snooping" of this kind, one is usurping the role of chance to some degree. In

summary, there does appear to be no evidence to support the presence of spatial

compatibility effects, for complex movements, which are not based on quite overt

relationships between the target position and the visual/body axis.

Page 184: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SUMMARY AND CONCLUSIONS

12.1 SUMMARY OF RESULTS Both experiments provided confihmation that the relationship between the spatial

location of the movement goal and the visual/body axis is associated with effects exerted

upon a variety of movement of parameters. These spatial compatibility effects did not

appear to reflect purely biomechanical constraints but may have arisen as a consequence of

the particular characteristics of "higher order" organization.

There was little evidence of asymmetries in response movements, other than in

terms of parameters possibly related to the nature of the impulses applied during the

initiation of movement, specifically the Peak Velocity of the movement and the movement

duration. The spatially complex nature of the response movement itself was conceived as

being one possible reason why preferred hand "advantages" were not exhibited. In

addition, anticipated asymmetries arising from processes related to the localization of

targets in extrapersonal space were not exhibited. The functional unity of perception and

action was stressed throughout, yet it was also suggested that suitable measures may

provide indications of the physical/physiological correlates of this behaviour. It may have

been the case that, indeed, the establishment of a target in space cannot be dissociated from

the preparation for action directed toward that spatial location.

Vision of the responding hand, in conditions in which ambient illumination was

present, was associated with an increased terminal accuracy of the movement, although

individuals were never afforded the opportunity to make a visual comparison of the relative

positions of the target and the responding hand. This increase in terminal accuracy was not

accompanied by increases in movement time. The possible means through which retinal

and extraretinal information may contribute to this regulation could not be delineated in this

study.

Page 185: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

12.2 CONCLUDING REMARKS

A substantial portion of the literature review was devoted to consideration of the

relative contributions of a variety of factors to what are observed as manual asymmetries. It

was tentatively concluded that a complete account of manual asymmetries would encapsulate a particular sensitivity to specific task demands and consider that, in particular,

as the nature of the movements studies equate more closely with the spatially oriented goal

directed behaviour characteristic of our daily lives, a proportionate increase in right

hemisphere involvement should be anticipated. The results of Experiments 1 and 2, whilst

providing no strong evidence in support of this claim, similarly did not encourage a

rejection of this approach.

In both experiments, advantages for the left hand, in terms of reaction time, although not statistically significant, may indicate an increased involvement of the right hemisphere, in terms of preparation for action which is spatially complex. There were also no benefits observed for the prefened right hand in terms of the final accuracy of the movement, in cases both in which visual information regarding the position of the responding hand was and was not available. Whilst there is always likely to be some

hazard in associating the theory with the null hypothesis, in that some encouragement is

provided for ill controlled experimentation, it may now be the case that, in the field of

motor control, theoretical positions may be sufficiently well defined and measurement techniques be of such precision, that a priori identification with the null hypothesis may be

possible. Meehl(1967) in stating, what was to become the paradox to bear his name, outlined

a substantial problem associated with the logic of psychological research: In the physical sciences, the usual result of an improvement in experimental design, instrumentation, or numerical mass of data, is to increase the difficulty of the 'observational hurdle' which the physical theory of interest must successfully surmount; whereas, in psychology and some of the allied behaviour sciences, the usual effects of such improvement in experimental precision is to provide an easier hurdle for the theory to surmount (p. 103).

Mendela (1972) has suggested a possible solution to this paradox, is to adopt the

conventional strategy of identifying with the alternative (non null) hypothesis until

experimental precision has increased to some criterion level, at which point a switch can be

made to a strategy where the theory is identified with the null hypothesis. One problem

with this approach, as Mendela (1972) acknowledges is selection of the time at which this

switch should occur. In addition, it is not necessary that there be adoption of a "point" null

hypothesis, which is itself nearly always false (Grant, 1962; Bakan, 1966), the alternative

is to select a bandwidth to be considered as null. Therefore, differences have to exceed this,

experimental as opposed to statistical, bandwidth. In order to achieve a practical 171

Page 186: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

implementation of this strategy, it may be necessary to design experiments such that, for

example, the theory of interest predicts no differences versus some differences (Wilson &

Miller, 1 964).

The utility of this strategy in the examination of manual asymmetries may be clearly

seen. If it indeed proves practically impossible to provide some manipulation of spatial complexity which is independent of other parameters of the movement, and therefore not

feasible to identify levels of complexity permitting examination of interactions, the

alternative may be to examine a series of movement types which are selected on the basis of

topological spatial complexity. Due to other intrinsic aspects of preparation and execution, it may be the case that, at this stage of phylogical development, at least for right handed

adults, a consistent population level left hand "advantage" in terms of, for example,

terminal accuracy, will not be exhibited even for the most spatially complex movements.

Therefore, it may only be possible to identify with the null hypothesis for spatially complex movements (as one cannot anticipate a left hand superiority of any appreciable magnitude to

arise from anything other than chance) and to predict some differences (in favour of the

right hand) for movements which are less spatially complex.

In view of the precision associated with the methodology current in examination of motor behaviour, such as that provided by sophisticated motion analysis systems, it may be possible to adopt as an experimental strategy, identification with a band null hypothesis. To

relate this directly to the present study, in a subsequent "replication", one might again suggest that no right hand advantage would be anticipated. In this case the theory is

identified directly with the null hypothesis and may be tested as such.

Clearly Experiment 2 provided indications that the environmental information

specifying the action goal exerted effects which recurred throughout the time course of the

resultant movement. Obviously this perception does not precede action. There are ways in

which attempts may be made to account for this behaviour in terms of a computational

model, through the formal specification of complex relationships, of a recursive nature,

assumed to link the "perceptual and motor systems". However, by adopting a commitment to "ecological realism" (Kugler, Kelso & Turvey, 1982) and a consideration of the animal-

environmental synergy, one precludes the need for consideration of formalized intermediate

relationships. The more general problem perhaps arises in conceiving of the stimulus as

something upon which the organism acts. As Merleau-Ponty suggests, when an individual

acquires a skill he: does not weld together individual movements and individual stimuli but acquires the power to respond with a certain type of solution to situations of a certain general form. The situations may differ widely from place to place,

1 7 2

Page 187: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

and the response movements may be entrusted sometimes to one operative organ, sometimes to another, both situations and responses in the various cases having in common not so much a partial identity of elements as a shared sigmficance. (1962, p. 142).

The significance in this case being that which affords the accomplishment of a previously

established task goal, in addition to the task goal itself. It may well be the case that

particular patterns of enviror&ental information provides less in the way of affordance, in

terms of that action than others, identifiably in this instance Pattern 3. The

comments of Dreyfus (1979) are particularly noteworthy in this regard: A machine can, at best, make a specific set of hypotheses and then find out if they have been confirmed or refuted by the data. The body can constantly modify its expectations in terms of a more flexible criterion: as embodied, we need not check for specific characteristics or a specific range of characteristics, but simply whether, on the basis of our expectations, we are coping with the object. (p. 250).

One can see how the affordaxes provided by visual/environrnental information pertaining

as to the position of the responding hand in extrapersonal space may be accommodated

within this perspective. It is not the case that there should exist an ideal or specified

trajectory, in Dreyfus's terms, "a range of characteristics", rather the individual may

regulate his action on the basis of expectations, not so much of the object, but of the

outcome of that action.

Whilst in theoretical terms, progress may be brought about by a shift in, or

reevaluation of the epistemological assumptions which accompany approaches in this area,

in more practical terms, in examining the physica.l/physiologica1 correlates of behaviour

described at the phenomenological level, the progress may be brought about by the

implementation of the use of a collection of dependent measures more likely sensitive to

characteristics of the physical/physiological substrate to be described

In the continued development of the present investigation, this may take the form of

application of jerk analysis as a means of directly assessing the relative variability in force

production for the two hands, some monitoring of muscular activity and analysis of the

biomechanical constraints inherent in contralateral and ipsilateral limb movements, as a

means of establishing the relative contributions of these factors to what may be regarded as

potent spatial compatibility effects, as well as continued integration of circumstantial

evidence, such as single cell recordings of cortical activity accompanying similar

movements. In addition,it seems imperative that there be an implementation of analysis of

oculomotor behaviour as an attempt to estimate the importance of optic flow and extra-

retinal information in establishing the positions of task goals in extrapersonal space and in

assessing the relative contributions of central and peripheral vision in the regulation and

modification of related limb movement. It should be reemphasized that this course of

Page 188: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

investigation may proceed entirely without need for recourse to intermediate "pseudo- explanatorytt constructs.

Page 189: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

APPENDIX A

SCHEMATIC REPRESENTATION OF PATI'ERN DISPLAY SEQUENCES.

FIGURE 1

TARGET

LINEAR

CUBIC

TARGET

TARGET v QUADRATIC

TARGET

Page 190: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

APPENDIX B

SCHEMATIC REPRESENTATION OF TARGET POSITIONS RELATIVE TO THE DISPLAY PANEL.

Page 191: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

APPENDIX C

PRELIMINARY ANALYSIS OF CROSSINGS OF THE ZERO ACCELERATION

PROFILE

Although custom designed WATSMART software was used with the intention of applying

a 30 Hz, low pass filter, there is some reason to be sceptical about the success of this

procedure. Examination of the data indicated that a high frequency 'noise' component may

have remained present in the signal. Although the instantaneous vector acceleration was

subject to succesive stages of smoothing, and the subsequent imposition of a windowing

filter, this was probably not entirely appropriate for the removal of the phasic noise

component. In this respect the data must be regarded as somewhat suspect. In view of what

would be associated problems in the interpretation of the measure of Zero Crossings, this

analysis may be considered as no more than suggestive, and as such has been included in

this appendix, rather than in the main body of the results. The analysis did appear to

indicate the presence of differences across levels of the factor of Pattern, however, in view

of the nature of the signal obtained, the evaluation of these trends should be approached

with caution. It is likely that the values presented represent overestimates of the number of

crossings.

Mean values for the number of crossings of the acceleration profile were obtained

from three trials within each of 128 cells constituting all possible combinations of the six

factors of Hand, Visual Condition, Visual Field, Pattern, Relation to Midpoint and Target

Eccentricity. A repeated measures ANOVA was performed on the mean scores, using a 2 x

2 x 2 x 4 x 2 x 2 factorial design.

The preliminary analysis indicated the presence of a main effect associated with the

factor of Hand, F(l, 7) = 6.60, p < 0.05, there were a greater number of zero crossings

when subjects performed movements with their left hand.

Page 192: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 1A Mean Number of Zero Crossings as a Function of Hand and Pattern.

Hand

Pattern Right Left mean

mean 6.3 7.5

There was also evidence of a main effect for the factor of Pattern, F(3,21) = 10.95,

p < 0.0005. It appeared that the mean number of crossings occurring during movements

made in response to pattern 3 was greater than during other presentation sequences, indeed,

a post hoc analysis, using the Tukey (HSD) procedure (Table l.lB), indicated that this

trend did achieve statistical ~ i ~ c a n c e at the 0.01 level, in cases of comparison with all

other levels of this factor.

TABLE 1.1A Mean Number of Zero crossing:^. Differences among: Pattern Means.

Page 193: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

HAND BY PATTERN

11 1

FIGURE 1A Mean Number of Zero Crossings by Hand and Pattern.

Most importantly, there was no main effect associated with the factor of Relation to

Midpoint, F(1, 7) = 0.02, p > 0.05, nor an statistically significant interaction of Hand and Visual Field, F(l, 7) = 3.41, p > 0.05. The presence of ambient illumination during the

course of the movement had no consistent effect on the number of zero crossings, F(1,7)

= 0.17, p > 0.05. Indeed, somewhat counter to intuition, the mean number of crossings was greater for the Non-illuminated condition (mean illuminated = 6.7, mean non-

illuminated = 7.1). No main effects corresponding to the remaining primary factors approached statistical significance at the 0.05 level.

Higher order interactions were however present. Hand interacted with the factor of

Relation to Midpoint, F(l, 7) = 6.43, p < 0.05. The relevant mean values are presented in

Table 2A, and are represented in Figure 2A

Page 194: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

TABLE 2A Number of Zero Crossings as a Function of Hand and Relation to Midpoint..

Hand

Midpoint Right Left mean

Lower

upper

mean 6.3 7.5

HAND BY MIDPOINT

* RIGHTHAND + LEFTHAND

FIGURE 2A

lower Upper

MIDPOINT

Mean Number of Zero Crossings by Hand and Relation to Midpoint.

Clearly, for movements made with the right hand, there were an increasing number

of zero crossings of the acceleration profile for targets located above the midpoint, whilst

for left-handed movements the tendency was reversed.

A three way interaction, of the factors of Visual Condition, Visual Field and

Relation to Midpoint, was also of statistical significance, F(l, 7) = 6.50, p < 0.05.

As suggested by examination of Figure 3A and by inspection of the mean values in

Table 3A, for movements made toward targets located in the right visual field, the number 180

Page 195: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

of zero crossings increased for upper targets relative to lower targets when ambient lighting

was not present, and decreased from lower to upper targets when illuminated In contrast,

for movements made into the left visual field, when illuminated the number of zero

crossings increased for upper targets relative to lower targets, yet for conditions in which

ambient lighting was not present the tendency was reversed.

TABLE 3A Number of Zero Crossings as a Function of Visual Condition. Visual Field

and Relation to Mid~oint.

Visual Condition

Illuminated Illuminated Non-illurn Non-illurn

Visual Field Left Right Left Right

Midpoint

Lower 6.0 7.1 7.0 7.3

Page 196: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

VISUAL CONDITION BY VISUAL FIELD BY MIDPOINT

LOWER UPPER

MIDPOINT

FIGURE 3A Mean Number of Zero Crossings by Visual Condition, Visual Field and

Relation to Midpoint.

Page 197: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

APPENDIX D

SUMMARY TABLES FOR ANALYSES OF VARIANCE, EXPERIMENTS 1 AND 2.

Page 198: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

ME

AN

E

RR

OR

ha

nd

E

RR

OR

fi

el

d

ER

RO

R

h f

ER

RO

R

co

mp

I x

ER

RO

R

h c

E

RR

OR

f c

E

RR

OR

hfc

E

RR

OR

mid

E

RR

OR

hm

E

RR

OR

fm

E

RR

OR

hfm

E

RR

OR

cm

E

RR

OR

hc

m

ER

RO

R

fcm

E

RR

OR

hf

cm

ER

RO

R

ec

c

ER

RO

R

he

E

RR

OR

fe

E

RR

OR

SU

M

OF

SQ

UA

RE

S

83

72

98

87

.69

53

1

35

56

93

1.4

29

69

11

28

7.5

31

25

1

43

11

1.2

18

75

21

78

.00

00

0

68

93

.43

75

0

30

3.1

95

3 1

3

70

1.3

67

19

36

82

9.8

82

8 1

8

54

48

.24

21

9

14

3.0

78

12

1

06

67

.92

18

8

21

26

.54

68

8

22

03

4.7

65

62

13

89

.57

03

1

92

13

.61

71

9

2.0

00

00

2

71

1.2

50

00

16

8.8

20

31

2

48

6.8

04

69

29

.07

03

1

18

12

.99

21

9

34

.03

12

5

53

89

.90

62

5

22

34

.67

18

7

27

74

1.5

78

12

25

3.1

95

31

1

20

27

.17

96

9

74

2.7

57

8 1

1

81

40

.67

96

9

26

36

.82

81

2

87

60

.73

43

7

17

.25

78

1

40

16

.17

96

9

30

6.2

81

25

3

54

2.4

06

25

1 2

8.0

00

00

1

04

25

.12

50

0

DE

GR

EE

S

OF

M

EA

N

FR

EE

DO

M

SQ

UA

RE

T

AIL

P

RO

6 .

0.0

00

0

0.4

81

6

0.1

80

6

0.4

73

6

0.0

52

7

0.9

62

6

0.5

76

7

0.3

88

9

0.9

44

7

0.5

12

8

0.7

47

4

0.8

39

5

0.6

44

8

0.9

30

2

0.8

34

5

0.1

29

8

0.0

67

2

0.4

62

1

0.7

77

9

GR

EE

NH

OU

SE

H

UY

NH

G

E I SS

ER

F

EL

OT

P

RO

0 .

PR

O6

.

Page 199: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hfe

E

RR

OR

c e

ER

RO

R

hc

e

ER

RO

R

fc

e

ER

RO

R

hf

ce

E

RR

OR

me

E

RH

OR

hrn

e E

RR

OR

f m

e

ER

RO

R

h f

me

E

RR

OR

cn

le

ER

RO

R

hc

me

E

RR

OR

f c

me

E

RR

OR

hf

cm

e

ER

RO

R

Page 200: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

SU

M

OF

S

QU

AR

ES

88

66

54

18

.40

82

0

10

01

37

64

.41

99

2

53

23

.83

00

8

16

54

83

.81

05

5

15

.47

07

0

42

32

.66

99

2

36

33

1.9

70

70

4

15

2.4

82

42

79

35

2.4

12

11

1

64

71

0.8

22

27

23

32

.42

77

3

20

23

7.9

94

14

50

7.0

05

86

1

85

14

.16

60

2

55

85

.06

83

6

26

48

6.7

9 1

02

01

22

9.6

89

45

1

08

15

.45

11

7

50

6.0

17

58

8

01

5.1

85

55

31

.50

19

5

15

93

1.8

26

17

31

95

.00

19

5

78

22

.13

86

7

54

86

.69

33

6

44

88

7.7

28

52

29

76

.86

52

3

21

78

4.4

94

14

33

2.2

24

61

1

02

94

.25

97

7

52

62

.09

96

1

20

24

5.5

72

27

25

4.5

33

20

6

71

0.0

44

92

3 1

7.2

05

08

1

43

9.9

35

55

33

46

.64

25

8

25

14

1.1

23

05

DE

GR

EE

S

OF

ME

AN

FR

EE

DO

M

SQ

UA

RE

T

AIL

P

RO

B .

0.0

00

1

0.6

49

6

0.8

77

4

0.0

00

1

0.0

37

7

0.5

04

2

0.9

00

9

0.2

49

8

0.0

00

2

0.5

27

5

0.9

09

7

0.1

34

7

0.4

79

3

0.4

31

5

0.8

77

3

0.1

74

5

0.6

22

2

0.2

54

3

0.3

66

6

GR

EE

NH

OU

SE

H

UY

NH

G

EI S

SE

R

FE

LD

T

PR

OB

. P

RO

B.

ME

AN

ER

RO

R

ha

nd

ER

RO

R

f le

ld

ER

RO

R

h f

ER

RO

R

co

mp

l x

ER

RO

R

h c

ER

RO

R

fc

ER

RO

R

hf

c

ER

RO

R

mid

ER

RO

R

hm

ER

RO

R

fm

ER

RO

R

hf

m

ER

RO

R

c m

ER

RO

R

hc

m

ER

RO

R

fcm

ER

RO

R

hf

cm

ER

RO

R

ec

c

ER

RO

R

he

ER

RO

R

fe

ER

RO

R

Page 201: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hf

e

ER

RO

R

ce

E

RR

OR

hc

e

ER

RO

R

f c

e

ER

RO

R

tlf

ce

E

RR

OR

me

E

RR

OR

hm

e

EH

RO

R

fme

E

RR

OR

hfm

e

ER

RO

R

c m

e E

RR

OR

hc

me

E

RR

OR

f c

me

E

RR

OR

hf

cm

e

ER

RO

R

Page 202: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

SUM

O

F SQ

UAR

ES

12

91

03

56

5.6

40

63

4

32

43

65

.70

31

2

32

10

8.1

60

16

1

59

70

7.2

77

34

27

6.3

90

62

1

06

14

3.6

71

87

25

69

.22

26

6

59

09

5.0

71

09

15

65

.19

14

1

14

41

4.1

21

09

l50

.06

25

0

55

34

.46

87

5

6.5

66

4 1

1

11

2.0

27

34

17

11

.89

06

3

70

45

.10

93

7

68

44

.00

78

1

23

67

1.2

73

44

36

2.3

00

78

1

44

86

.13

67

2

91

6.0

39

06

1

54

54

.89

84

4

17

26

.64

45

3

22

17

8.7

61

72

88

3.9

41

41

4

87

4.9

96

09

38

9.0

70

3 1

1

53

70

.64

84

4

16

98

.97

26

6

10

53

2.5

58

59

24

70

.58

59

4

21

36

6.7

89

06

43

8.3

78

9 1

1

18

14

.62

10

9

3.0

62

50

6

91

9.3

43

75

21

21

.75

39

1

46

14

.33

98

4

DE

GR

EE

S

OF

MEAN

FR

EEO

OM

SQ

UAR

E

HU

VN

H

FE

LD

T

PR

OB

.

GR

EEN

HO

USE

GE

ISS

ER

P

RO

0 .

MEAN

ER

RO

R

ha

nd

ER

RO

R

i l lu

m

ER

RO

R

hi

ERRO

R

fie

ld

ER

RO

R

h f

ERRO

R

if

ER

RO

R

hif

ERRO

R

com

p l x

ERRO

R

hc

ERRO

R

i c

ER

RO

R

hic

ERRO

R

fc

ERRO

R

hfc

ERRO

R

if

c

ER

RO

R

hif

c

ERRO

R

tn i d

E

RR

OR

hn

E

RR

OR

Page 203: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Experiment 2: Median RT B

o m - P Or- o m - m 0 0 O N P O O h 0 0 0 0 0 - w - m m o m - w o r c m m - N - a o w m o o m N N m m o m ~ m W N o m . . . . . . . . . . . . o m a - N m O N O N - m - w P W m o 0 0 m - h m - w m o m a m - 0 o

m ~ m - ? m m o

Page 204: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hife

E

RR

OR

ce

E

RR

OR

hc

e

ER

RO

R

ic

e

ER

RO

R

h l c

e

ER

RO

R

fc

e

ER

RO

R

hf

ce

E

RR

OR

if

ce

E

RR

OR

hi

fc

e

ER

RO

R

me

E

RR

OR

hm

e

ER

RO

R

i me

E

HR

OR

t> i m

e

ER

RO

R

f m

e

EH

RO

R

hf

me

E

RR

OR

ifm

e

ER

RO

R

hif

me

E

RR

OR

c m

e

ER

RO

R

hc

me

E

RR

OR

i cm

e

ER

RO

R

Page 205: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

h l c

me

E

RR

OR

f cr

ne

ER

RO

R

hfc

me

E

RR

OR

i f c

me

E

RR

OR

hif

cm

e

ER

RO

R

Page 206: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

SU

M

OF

SQ

UA

RE

S

19

18

32

88

7.6

40

63

1

09

64

69

5.7

81

25

29

96

19

.39

06

2

13

86

22

.50

00

0

11

55

6.2

50

00

1

26

07

97

.73

43

8

43

.89

06

3

35

83

8.5

62

50

53

74

.72

26

6

57

88

9.0

11

72

69

79

5.0

35

16

3

45

15

.10

54

7

57

9.0

03

9 1

3

28

54

.66

79

7

15

95

.00

39

1

18

52

8.5

74

22

16

20

43

3.1

95

31

1

01

47

52

.69

53

1

32

57

.86

71

9

87

36

1.5

54

69

48

08

9.6

64

06

4

15

11

4.4

14

06

15

80

.50

78

1

34

17

9.3

51

56

70

76

.59

76

6

43

55

2.3

55

47

71

50

.33

20

3

66

29

1.4

64

84

15

94

.20

70

3

26

71

7.3

08

59

59

66

.87

89

1

45

24

8.2

30

47

16

28

12

.25

00

0

10

50

10

.48

43

8

15

3.1

40

63

1

31

90

.50

00

0

15

21

.00

00

0

26

80

1.4

21

88

DE

GR

EE

S

OF

ME

AN

F

T

AIL

G

RE

EN

HO

US

E

HU

VN

H

FR

EE

DO

M

SQ

UA

RE

P

RO

0 .

GE

I SS

ER

F

ELD

T

PR

O0 .

PR

OB

. 0

.00

00

0.0

06

0

0.8

07

3

0.9

28

8

0.4

46

7

0.0

07

1

0.7

35

8

0.4

63

0

0.0

00

1

0.0

07

3

0.0

05

4

0.8

52

6

0.7

01

5

0.7

37

3

0.5

02

0

0.4

22

6

0.4

34

4

0.8

08

2

0.7

24

6

0.7

89

0

0.3

56

8

0.3

49

1

0.3

56

3

0.5

31

8

0.4

38

1

0.4

49

8

0.7

42

1

0.6

99

4

0.7

42

1

0.4

46

8

0.4

14

1

0.4

33

8

0.0

13

2

0.7

83

8

0.5

48

5

ME

AN

ER

RO

R

ha

nd

ER

RO

R

i l lu

m

ER

RO

R

hi

ER

RO

R

fie

ld

ER

RO

R

hf

ER

RO

R

i f

ER

RO

R

hi f

ER

RO

R

co

mp

l x

ER

RO

R

h c

ER

RO

R

i c

ER

RO

R

hi

c

ER

RO

R

f c

ER

RO

R

hfc

ER

RO

R

if

c

ER

RO

R

hif

c

ER

RO

R

mid

ER

RO

R

hm

ER

RO

R

i m

ER

RO

R

Page 207: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

2 m 0

0

N m m

a 0 w(3 NU) r - m m a . . r- - m m m - m N

- r-

- m N 0

0

N a 0 0

0

m 0 0 0

0

o m 3

r-a r - m - a m N P N . . a 0 0 0 m w 0 0

0 - N

Experiment 2: Median MT B

0 m a m 0

f- m P m 0

t- o m m 0

P 0

0

m o P a P - mu7 m - . . QU) m o

n N

m - N

m 0 m P

0

0 r-

0

N m a P m a - 0 0 0 . . - 0 - 0, r - m N O

- r-

O N - r - a - W N ~ f - - - - a 0 3 w - m ~ W N a h m m N O o m O N or- a - -I- ar- m w m q a q W N - P o m m o m ~ o m ~ m - N - o ~ m uag ~5 g; m m W P o m a o ~ m o m N O m a 0 0 a f - N P o m p a m ~ 0 0 m m N P - 0 O N h N a - o m r - m r - m m m o m m w o w $ 2 m a 2 s m o a m - N W - 0 - a m P o a - m v a m m o m w m - f -P P - o w m a P O m m ~a m - 0 - m - N O o m m - o m m o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a a m m - 0 + m 0 0 m ~ m o m - m ~ - 0 m m N O m m r - m ~ m or- m m N N m m m ~ N O - m o m o f - m o - o a o m - m o m m W P N - m o - o v o - m m - - m - a f - o O N m ~ - 0 3 0 n o -1 - w m ~ O P N N ~ m f -N ~ m ~ m m m m m - o o

m h m a m ~ m ~ f - a - N o m - N - P N G m ~ r - - - o N m o m - - P N - m - a N m a - T N O m N - - - - - -

a a X K K K K E K x a a a a a o o o O E O o o o E o 0 E 0 E o u o o o o o o o

E a a E a E K L K a E K E a u a E a u a u a e a u p r a m a a m ~ a a - a E a e a - a - a E K - a u a % a % K - a u u m a m a - a m a e a + a

e w c u - w r w u w :?i .:$ r w + u ,w - w r u m u r w - w r w L w r w - w

Page 208: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

t~

if

e

ER

RO

R

c e

ER

RO

R

hc

e

ER

RO

R

ic

e

ER

RO

R

hi c

e

ER

RO

R

fc

e

ER

RO

R

hf

ce

E

RR

OR

if

ce

E

RR

OR

hi

fc

e

ER

RO

R

me

E

RR

OR

hm

e

ER

RO

R

i me

E

RR

OR

him

e

ER

RO

R

fme

E

RR

OR

hfm

e

ER

RO

R

i f

me

E

RR

OR

hif

me

E

RR

OR

c m

e

ER

RO

R

hc

me

E

RR

OR

i c

ine

E

RR

OR

Page 209: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hi

cm

e

6 0

E

RR

OR

f c

me

6

1

ER

RO

R

hf

cme

62

E

RR

OR

i f

ctn

e 6

3

ER

RO

R

hifcme

6 4

ER

RO

R

Page 210: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

SU

M

OF

SQ

UA

RE

S

16

25

31

6.4

98

40

6

35

55

.53

02

9

16

2.1

44

73

3

52

8.8

90

88

27

71

9.1

94

33

2

42

96

.36

63

7

54

.A6

24

4

17

79

.10

55

1

26

53

.70

83

5

23

32

0.5

56

19

27

.72

47

0

87

64

.85

53

5

45

8.0

32

97

9

48

8.2

33

99

36

9.1

38

18

2

31

9.9

36

41

87

7.4

78

59

1

25

58

.88

71

1

54

4.2

24

08

3

29

4.4

15

93

14

07

.29

23

1

37

48

.92

87

8

53

.00

69

4

36

99

.87

64

4

6 1

6.7

58

56

2

34

1.1

88

66

33

0.2

13

35

2

08

9.0

22

82

21

5.5

06

91

2

58

1.7

56

37

22

7.2

55

8 1

2

95

1.5

70

16

31

7.4

49

47

2

62

05

.08

30

7

14

0.9

79

08

4

58

8.6

41

48

20

57

.74

77

8

10

76

9.3

58

26

DE

GR

EE

S

OF

ME

AN

FR

EE

DO

M

SQ

UA

RE

T

AIL

G

RE

EN

HO

US

E

HU

VN

H

PR

O0 .

GE

1 SSER

F

ELD

T

PR

OB

. P

RO

B .

0.0

00

0

ME

AN

ER

RO

R

han

d

ER

RO

R

il lu

m

ER

RO

R

hi

ER

RO

R

fie

ld

ER

RO

R

h f

ER

RO

R

if

ER

RO

R

hi

f

ER

RO

R

co

mp

I x

ER

RO

R

h c

ER

RO

R

i c

ER

RO

R

hi

c

ER

RO

R

f c

ER

RO

R

hf

c

ER

RO

R

if

c

ER

RO

R

hi

fc

ER

RO

R

mid

ER

RO

R

hm

ER

RO

R

i In

ER

RO

R

Page 211: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

him

E

RR

OR

fm

E

RR

OR

hf

m

ER

RO

R

if

m

ER

RO

R

hi

fm

E

RR

OR

c m

E

HR

OR

hc

m

ER

RO

R

i cm

E

RR

OR

hi c

m

ER

RO

R

fcm

E

RR

OR

hf

cm

E

RR

OR

i fc

m

ER

RO

R

hif

cm

E

RR

OR

ec

c

ER

RO

R

he

E

RR

OR

1 e

ER

RO

R

hi

e

ER

RO

R

fe

E

RR

OR

hf

e

EH

RO

R

if

e

ER

RO

R

Page 212: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hi

fe

E

RR

OR

ce

E

RR

OR

hc

e

ER

RO

R

ic

e

ER

RO

R

hi c

e

ER

RO

R

fc

e

ER

RO

R

hf

ce

E

RR

OR

if

ce

E

RR

OR

hi

fc

e

ER

RO

R

me

E

RR

OR

hm

e

ER

RO

R

i m

e

ER

RO

R

him

e

ER

RO

R

f m

e

ER

RO

R

hfm

e

ER

RO

R

ifm

e

ER

RO

R

hc

me

E

RR

OR

i cm

e

ER

RO

R

Page 213: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hfc

me

60

ER

RO

R

f c

me

6 1

E

RR

OR

hf

cm

e

6 2

E

RR

OR

i f

cm

e

6 3

E

RR

OR

ti1

fcm

e

6 4

E

RR

OR

Page 214: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

S

UM

O

F

SQ

UA

RE

S

42

25

58

.48

28

1

37

85

8.9

32

27

47

.46

22

0

14

83

-9

98

23

50

5.8

14

40

4

93

7.2

88

06

29

4.4

90

67

1

62

8.5

08

73

13

60

1.9

44

51

1

42

80

3.6

05

29

42

.39

50

4

29

33

4.6

64

11

10

23

2.9

42

86

5

77

27

.23

55

3

17

9.4

12

1 1

1

43

92

.81

56

5

69

76

.56

34

3

70

65

.33

10

3

58

2.5

18

83

2

81

6.9

12

38

53

4.9

72

06

1

65

0.5

06

99

43

6.6

89

92

3

02

6.5

13

05

20

53

.72

97

9

67

10

.94

58

1

34

3.5

40

08

2

14

8.2

03

72

12

7.3

03

33

1

99

3.8

04

70

33

7 .

a6

37

2

26

52

.63

64

6

34

.56

82

6

60

12

.02

34

3

17

9.8

75

50

9

62

.01

69

4

15

.32

64

1

29

0.9

57

71

DE

GR

EE

S

OF

M

EA

N

F

TA

IL

GR

EE

NH

OU

SE

H

UV

NH

P

RO

B .

GE

1 S

SE

R

FE

LD

T

PR

O0

. P

RO

B.

78

.13

0

.00

00

FR

EE

DO

M

1

7 I

7 1

7

1 7 I

7

1

7 1

7 1

7

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1 1

7

1

7 1

7

SQ

UA

RE

42

25

58

.48

28

1

54

08

.41

89

0

47

.46

22

0

21

1.9

99

75

50

5.8

14

40

7

05

.32

69

8

29

4.4

90

67

2

32

.64

41

0

13

60

1.9

44

51

2

04

00

.51

50

4

42

.39

50

4

41

90

.66

63

0

10

23

2.9

42

86

8

24

6.7

47

93

17

9.4

12

1 1

2

05

6.1

16

52

23

25

.52

11

4

33

6.4

44

33

19

4.

17

29

4

13

4.1

38

68

17

8.3

24

02

7

8.5

95

57

14

5.5

63

31

1

44

. 1

19

67

68

4 -

57

66

0

3 l

9.5

68

O5

11

4.5

13

36

1

02

.29

54

2

42

.43

44

4

94

.94

30

8

11

2.6

21

24

1

26

.31

60

2

34

.56

82

6

85

8.8

60

49

17

9.8

75

50

1

37

.43

09

9

15

.32

64

1

4 1

.56

53

9

ME

AN

E

RR

OR

ha

nd

E

RR

OR

i I l u

tn

ER

RO

R

ti i

ER

RO

R

fi

el

d

ER

RO

R

h f

E

RR

OR

i f

E

RR

OR

hi

f

ER

RO

R

co

mp

l x

ER

RO

R

h c

E

RR

OR

i c

ER

RO

R

hic

E

RR

OR

fc

E

RR

OR

hf

c

ER

RO

R

if

c

ER

RO

R

hi

fc

E

RR

OR

mid

E

RR

OR

hm

E

RR

OR

i m

E

RR

OR

Page 215: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

h i

m

ER

RO

R

f m

E

RR

OR

hf

m

ER

RO

R

if

m

ER

RO

R

hi

fm

E

RR

OR

cm

E

RR

OR

tic

m

ER

RO

R

i cm

E

RR

OR

tiic

m

ER

RO

R

fcm

E

RR

OR

hf

cm

E

RR

OR

ifc

m

ER

RO

R

hif

cm

E

RR

OR

ec

c

ER

RO

R

he

E

RR

OR

i e

ER

RO

R

hi

e

ER

RO

R

fe

E

RR

OR

hf

e

ER

RO

R

it

e

ER

RO

R

Page 216: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hi

fe

E

RR

OR

Lt)

ER

RO

R

hc

e

ER

RO

R

ic

e

ER

RO

R

hi

ce

E

RR

OR

fc

e

ER

RO

R

hf

ce

E

RR

OR

if

ce

E

RR

OR

hi

fc

e

ER

RO

R

me

E

RR

OR

hm

e

ER

RO

R

i me

E

RR

OR

him

e

ER

RO

R

hf

me

E

RR

OR

ifm

e

ER

RO

R

h i f

rne

ER

RO

R

cin

e

ER

RO

R

hc

me

E

RR

OR

i cm

e

ER

HO

R

Page 217: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

a m N h 9 0 or- o m P(0 - a or- 0 0 (Om - - N - - -

o - m - o - o - o - N N N N N

(0 - m m 0 0 m o lnd 0 0 'a- or- m l n lno o o r-o P O r-d -in - a NO) m o n o m v m m r -N o o m ~ r-r-

0 - m a O N - m o m P O O N o m m o m o - P o m mu, o w - 0

- O O N N

m a x x ma ola E K E 0 S O € 3 U O u x g Z u a u a h a - c U X e x e X - x T W r W . C W - W X U

Experiment 2: X Constant Error D

Page 218: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Experiment 2: X Variable Error A

o m m m m w - - U J m t - O m m N - N O - m O m w w o m - m o m o m

0 I

m o W a W W - c -r - - c - r - r - - r - - b - - 0 - m - m - o - m - m - m - m - a u N N N N N N N N o a W LL a

W I u a a a a a a - a a a a a a a a a 20 0 0 10 0 - 0 0 0 0 a 0 0 0 0 0 0 0 U O

u a c a - a a a a a e a E a a a a a u a u a r a o W D ma - a - a - a e a r a - a o a u a u a - a u a e a & a - a lA f W S W - W S W + W S W - U S W U W K U - W S W e W L W - U K W

Page 219: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

S

UM

O

F S

QU

AR

ES

24

12

.29

22

8

20

07

84

.34

26

1

67

14

.68

97

7

12

39

8.6

08

03

19

42

3.7

86

97

1

34

03

5.3

79

70

11

23

.54

12

7

13

00

6.6

00

73

41

-3

81

00

2

13

0.4

47

89

43

.33

34

3

15

25

.07

85

5

2 1

3.7

83

96

1

36

6.2

47

59

0.6

52

57

3

13

.17

36

8

76

3.3

29

25

1

34

72

.98

46

7

85

3.9

98

12

2

05

7.2

98

03

36

6.4

72

26

3

00

3.1

90

28

14

9.8

84

46

2

18

4.3

38

41

13

09

.87

71

5

13

94

.38

42

8

59

2.1

30

72

1

07

5.5

66

11

16

1.5

92

72

2

12

6.6

65

34

19

5.9

97

25

2

05

4.8

24

19

22

10

70

.81

32

6

24

07

5.6

74

78

35

.39

62

4

29

20

.04

15

7

63

7.1

15

96

6

23

1.5

81

88

DE

GR

EE

S

OF

M

EA

N

TA

IL

PR

OB

.

0.7

80

2

0.0

92

6

0.3

47

4

0.4

62

3

0.7

23

2

0.6

69

1

0.3

30

1

0.9

07

3

0.7

56

8

0.0

58

7

0.4

80

0

0.6

99

4

0.0

02

6

0.0

24

2

0.6

65

4

0.5

81

3

0.0

00

1

0.7

79

3

0.4

25

5

GR

EE

NH

OU

SE

G

El S

SE

R

PR

OB

.

HU

VN

H

F E

LD

T

PR

OB

. F

RE

ED

OM

1

7 1

7 1

7 1

7 1

7 1

7 1

7 I

7

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

1

7 1

7 1

7

SQ

UA

RE

24

12

.29

22

8

28

68

3 .'

I77

52

67

14

.6H

97

7

17

71

.22

97

2

19

42

3.7

86

97

1

91

47

.91

13

9

11

23

.54

12

7

18

58

.08

58

2

41

.38

10

0

30

4.3

49

70

43

.33

34

3

21

7.8

68

36

21

3.7

83

96

1

95

.17

82

3

0.6

52

57

4

4.7

39

10

25

4.4

43

08

6

4 1

.57

07

0

28

4.6

66

04

9

7.9

66

57

12

2.1

57

42

1

43

.00

90

6

49

.96

14

9

10

4.0

16

1 1

43

6.6

25

72

6

6.3

99

25

19

7.3

76

91

5

1.2

17

43

53

.86

42

4

10

1 .2

69

78

65

.33

24

2

97

.a4

87

7

22

10

70

.81

32

6

34

39

.38

21

1

35

.39

62

4

41

7.1

48

80

63

7.

11

59

6

89

0.2

25

98

ME

AN

E

RR

OR

ha

nd

E

RR

OR

i 1

1 ur

n E

RR

OR

hi

E

RR

OR

fie

ld

E

RR

OR

h f

ER

RO

R

if

E

RR

OR

hi

f

ER

RO

R

co

mp

1 x

ER

RO

R

h c

E

RR

OR

i c

ER

RO

R

hic

E

RR

OR

fc

E

RR

OR

hfc

E

RR

OR

if

c

ER

RO

R

hif

c

ER

RO

R

nl i d

E

RR

OR

hm

E

RR

OR

i m

ER

RO

R

Page 220: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

him

2 0

E

RR

OR

fm

2 1

ER

RO

R

hf

m

2 2

ER

RO

R

if

m

23

E

RR

OR

hi

fm

2

4

ER

RO

R

c m

2

5

ER

RO

R

hc

m

26

E

RR

OR

i cm

2

7

ER

RO

R

hic

m

28

E

RR

OR

fcm

2

9

ER

RO

R

h P

cln

3

0

ER

RO

R

ifc

m

3 1

E

RR

OR

hif

cm

3

2 E

RR

OR

ec

c

33

E

RR

OR

he

3 4

E

RR

OR

i e

35

E

RR

OR

hie

3 6

E

RR

OR

fe

3 7

E

RR

OR

hfe

3

8

ER

RO

R

If

a

3 9

E

RR

OR

Page 221: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hi

fe

E

RR

OR

c e

ER

RO

R

hc

e

ER

RO

R

ic

e

ER

RO

R

hi c

e

ER

RO

R

fc

e

ER

RO

R

hf

ce

E

RR

OR

if

ce

E

RR

OR

hi

fc

e

ER

RO

R

me

E

RR

OR

hm

e

ER

RO

R

i me

E

RR

OR

him

e

ER

RO

R

fme

E

RR

OR

hf

me

E

RR

OR

ifm

e

ER

RO

R

t~ i f

we

E

RR

OR

cm

e

ER

RO

R

hc

me

E

RR

OR

i cm

e

ER

RO

R

Page 222: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

h i c

me

6

0

ER

RO

R

f c

me

6

1

ER

RO

R

hf

cm

e

62

E

RR

OR

i f

cm

e

6 3

E

RR

OR

hi f

cn

~e

6 4

ER

RO

R

Page 223: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

S

UM

O

F

SQ

UA

RE

S

DE

GR

EE

S

OF

F

RE

ED

OM

M

EA

N

SQ

UA

RE

F

T

AIL

G

RE

EN

HO

US

E

PR

O8

. G

EI S

SE

R

PR

OB

. 2

17

.12

0

.00

00

HU

VN

H

FE

LD

T

PR

OB

. M

EA

N

ER

RO

R

ha

nd

E

RR

OR

i l lum

ER

RO

R

hi

ER

RO

R

fi

el

d

ER

RO

R

hf

E

RR

OR

if

E

RR

OR

hi

f

ER

RO

R

co

mp

l x

ER

RO

R

h c

ER

RO

R

i c

E

RR

OR

hi

c

ER

RO

R

fc

E

RR

OR

hf

c

ER

RO

R

if

c

ER

RO

R

hi

fc

E

RR

OR

Page 224: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

SUM

O

F SQ

UAR

ES

48

51

4.6

39

55

2

54

07

.29

71

7

33

1.1

64

07

3

51

.08

31

0

4 1

.84

47

4

16

94

.02

03

4

18

.50

79

1

15

1.1

98

E~

7

9 1

.04

34

3

35

0.

19

34

0

89

.85

45

3

18

4.5

53

34

0.0

62

50

1

05

.64

06

0

7.5

62

50

8

0.2

14

40

24

21

.50

67

8

15

47

.64

65

1

27

.82

84

4

18

9.5

22

98

93

.0 1

33

2

76

9.2

72

00

52

.81

53

9

16

9.9

96

99

46

.53

55

6

24

8.9

99

92

35

.11

84

7

2 1

0.3

22

44

25

.16

40

5

80

.38

79

7

54

.72

74

1

14

6.2

92

49

0.5

78

23

2

18

.46

68

6

63

. 5

00

93

6

9.1

00

53

3.7

13

64

4

9.4

55

58

DE

GR

EE

S

OF

MEAN

F

T

AIL

G

REEN

HO

USE

HU

VN

H

PR

OB

. G

EI S

SER

F

ELD

T

PR

O0 .

PR

O0 .

13

.37

0

.00

81

FR

EED

OM

1 7 1 7

1

7 1

7 1

7

1

7

1

7

1 7 3

2 1

3

2 1

3

2 1

3

2 1 3

2

1

3

2 1

3

2 1

3

2 1

1

7

1

7

1 7

SQ

UAR

E

40

51

4.6

39

55

3

62

9.6

13

88

33

1.1

64

07

5

0.1

54

73

4 1

.84

47

4

24

2.0

02

9 1

18

.50

79

1

2 1

.59

98

O

9 1

.O4

34

3

50

.O2

76

3

89

.85

45

3

26

.36

47

6

0.0

62

50

1

5.0

91

51

7.5

62

50

1

1.4

59

20

80

7.1

68

93

7

3.6

97

45

9.2

76

15

9

.02

49

0

3 1

-00

44

4

36

.63

20

0

17

.60

51

3

8.0

95

09

15

.51

18

5

11 .a

57

14

11

.70

61

6

10

.01

53

5

8.3

80

02

3

.82

80

0

18

.24

24

7

6.9

66

31

0.5

78

23

3

1 .2

09

55

63

.50

09

3

9.8

71

50

3.7

13

64

7

.06

50

8

MEAN

ERRO

R

hand

ERRO

R

I1

lum

ER

RO

R

hi

ER

RO

R

f ield

ERRO

R

h f

ERRO

R

if

ERRO

R

hi f

ERRO

R

co

mp

l x

ERRO

R

h c

ER

RO

R

i c

ERRO

R

hi c

ERRO

R

f c

ER

RO

R

hf c

ERRO

R

ifc

ER

RO

R

hifc

ERRO

R

mid

ER

RO

R

hm

ERRO

R

I m

E

RR

OR

Page 225: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

him

E

RR

OR

fm

ER

RO

R

hfm

E

RR

OR

if

m

ER

RO

R

hif

m

ER

RO

R

cm

E

RR

OR

hc

m

ER

RO

R

i cm

E

RR

OR

hi cm

E

RR

OR

fcm

E

RR

OR

hf

cm

E

RR

OR

ifc

m

ER

RO

R

hif

cm

E

RR

OR

ec

c

ER

RO

R

he

E

RR

OR

i e

E

RR

OR

hi

e

ER

RO

R

fe

E

RR

OR

hf

e

ER

RO

R

if

e

ER

RO

R

Page 226: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hl

fe

E

RR

OR

c e

ER

RO

R

hc

e

ER

RO

R

ice

E

RR

OR

ti i

ce

E

RR

OR

fe

e

ER

RO

R

hf

ce

E

RR

OR

if

ce

E

RR

OR

hi

fc

e

ER

RO

R

me

E

RR

OR

hm

e

ER

RO

R

i me

E

RR

OR

him

e

ER

RO

R

f m

e

ER

RO

R

hfm

e

ER

RO

R

i f

me

E

RR

OR

ti i

f m

e

ER

RO

R

cm

e

ER

RO

R

hc

me

E

RR

OR

i cm

e

ER

RO

R

Page 227: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Experiment 2: Zero Crossings D

Page 228: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

SU

M

OF

SQ

UA

RE

S

32

16

67

,32

73

5

10

27

8,1

79

40

18

16

,72

06

8

32

02

,82

12

0

97

8,7

49

1 1

1

10

6,9

53

93

0,9

65

22

6

19

,55

62

0

15

.66

05

3

98

7.3

49

84

12

44

.83

07

4

11

06

.77

60

9

5,0

26

20

4

34

,49

75

8

12

0,7

70

64

3

68

,25

78

5

85

7.4

17

91

2

43

0,4

96

09

32

3.6

49

76

1

43

8.1

34

40

24

.90

07

2

88

1,1

61

89

34

,65

73

5

10

37

.56

67

5

20

2,6

24

98

1

98

3.4

35

11

34

3.2

67

33

1

61

5.8

79

49

44

2.3

15

69

1

67

4.2

86

09

40

5.4

89

36

1

85

5.1

46

11

DE

GR

EE

S

OF

ME

AN

F

T

AIL

G

RE

EN

HO

US

E

HU

VN

H

PR

OB

. G

E I

SS

ER

F

ELD

T

PR

OB

. P

RO

B.

21

9.0

7

0.0

00

0

SQ

UA

RE

32

16

67

.32

73

5

14

68

.31

13

4

18

16

.72

06

8

45

7.5

45

89

97

8.7

49

1 1

15

8.1

36

28

0.9

65

22

8

8.5

08

03

15

.66

05

3

14

1.0

49

98

12

44

.83

07

4

15

8.1

10

87

5 .O

Z62O

6

2.0

71

08

12

0.7

70

64

5

2.6

08

26

28

5.8

05

97

1

15

.73

79

1

10

7.8

83

25

6

8.4

82

59

8.3

00

24

4

1 .9

6O

O9

1 1

.55

24

5

49

.40

60

4

67

.54

16

6

94

.4

49

29

11

4.4

22

44

7

6.9

46

64

14

7.4

38

56

7

9.7

27

91

13

5.1

63

12

8

8.3

40

29

ME

AN

ER

RO

R

ha

nd

ER

RO

R

I1

lum

ER

RO

R

hi

ER

RO

R

fie

ld

ER

RO

R

hf

ER

RO

R

if

ER

RO

R

hi

f

ER

RO

R

co

mp

l x

ER

RO

R

h c

ER

RO

R

i c

ER

RO

R

hic

ER

RO

R

fc

ER

RO

R

hfc

ER

RO

R

if

c

ER

RO

R

hif

c

ER

RO

R

Page 229: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

SO

UR

CE

SUM

OF

SQ

UAR

ES

59

35

.91

50

6

92

.12

35

2

8.7

51

62

2

.49

57

3

0.2

81

03

1

6.2

73

50

0.0

00

19

1

.66

54

2

0.2

64

33

0

.23

50

9

5.1

92

44

0

.48

18

2

0.1

10

38

0

.10

84

1

0.0

00

38

0

.O7862

4.9

70

51

3

.74

68

0

0.1

45

06

0

.75

28

2

0.2

45

09

0

.65

78

1

0.1

64

78

0

.34

49

3

0.0

65

60

0

.51

29

8

0.1

77

00

0

.45

33

2

0.0

36

9 1

0

.46

47

1

0.0

14

59

0

.39

41

2

14

.56

98

1

1 .6

54

46

0.0

07

24

0

.20

83

1

0.0

25

27

0

.10

90

7

DEG

REES

OF

FR

EED

OM

1 7

1 7

1

7

1 7

1 7

1 7 1 7

1 7

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

3

2 1

1 7

1 7

1

7

MEAN

SQ

UAR

E

59

35

.91

50

6

13

.16

05

0

8.7

51

62

0

.35

65

3

0.2

81

03

2

.32

47

9

0.0

00

19

0

.23

79

2

0.2

64

33

0

.03

35

8

5.1

92

44

0

.06

88

3

0.

11038

0.0

1549

0.0

00

38

0

.01

123

1 .6

56

84

0

.17

84

2

0.0

48

35

0

.03

58

5

0.0

81

70

0

.03

13

2

0.0

54

93

0

.01

64

3

0.0

21

87

0

.O2443

O.O

59O

O

0.0

21

59

0.0

12

30

0

.02

2 1

3

0.0

04

86

0

.01

07

7

14

.56

98

1

0.2

36

35

0.0

07

24

0

.02

97

6

0.0

25

27

0

.01

55

8

TA

IL

PR

O0 .

0.0

00

0

0.0

01

6

0.7

38

3

0.9

78

1

0.0

26

3

0.0

00

1

0.0

32

0

0.8

60

1

0.0

00

4

0.2

85

6

0.0

78

5

0.0

38

7

0.4

60

0

0.0

69

4

0.6

49

9

0.8

54

0

0'.

00

0 1

0.6

36

9

0.2

43

5

GR

EEN

HO

USE

GE

l SSER

P

RO

B.

O.O

O5O

0.2

91

5

0.0

82

6

0.0

83

6

0.4

06

3

0.0

97

4

0.6

02

0

0.7

87

6

HU

VN

H

FE

LD

T

PRO

B .

0.0

02

1

0.2

88

9

0 -0

78

5

0.0

70

0

0.4

20

2

0.0

71

1

0.6

49

9

0.8

54

0

MEAN

ERRO

R

ha

nd

ERRO

R

{ll

um

ERRO

R

hi

ERRO

R

f ie

ld

ERRO

R

hf

ERRO

R

if

ERRO

R

hi

f ERRO

R

cam

p l

x ERRO

R

h C

ERRO

R

i c

ERRO

R

hi

c ERRO

R

fc

ERRO

R

hfc

ERRO

R

if

c

ERRO

R

hif

c

ER

RO

R

mld

E

RH

OR

hm

ERRO

R

i m

ERRO

R

Page 230: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

him

E

RR

OR

fm

ER

RO

R

hf

m

ER

RO

R

1 f

m

ER

RO

R

hi

fm

E

RR

OR

c m

E

RR

OR

hc

m

ER

RO

R

i c

m

ER

RO

R

hic

m

EH

RO

R

fcm

E

RR

OR

hf

cm

E

RR

OR

ifc

m

ER

RO

R

hi

fc

~n

E

RR

OR

ec

c

ER

RO

R

he

E

RR

OR

i e

ER

RO

R

hi

e

ER

RO

R

fe

E

RR

OR

hf

e

EH

RO

R

if

e

tRR

OR

Page 231: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

hif

e

ER

RO

R

ce

E

RR

OR

hc

e

ER

RO

R

ic

e

ER

RO

R

hi c

e

ER

RO

R

f c

e

ER

RO

R

hf

ce

E

RR

OR

if

ce

E

RR

OR

hi f

ce

E

RR

OR

me

E

RR

OR

hm

e

ER

RO

R

i me

E

RR

OR

hi m

e

ER

RO

R

fme

E

RR

OR

hf m

e

ER

RO

R

ifm

e

ER

RO

R

hif

me

E

RR

OR

cm

e

ER

RO

R

hc

me

E

RR

OR

i cm

e

ER

RO

R

Page 232: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Experiment 2: Time to Peak Velocity D

n m r-lo cnO 3 - m a 0 - o m n m O N l n m

" N g z ;g ? < ZEl ,- 0 0 0 0 0 0 0 0 0 0 . . . . . . . .

m - m - m - m - m - N N N N N

m - N - m a a o a m h m ~ m cnm c n q m - a~ m m iolo m ~ - m O - m a N - O F m q O N O N 0 0 0 - O l n . . . . . . . . . . 0 0 0 0 0 0 0 0 0 0

Page 233: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

REFERENCE NOTES

Note 1: Peters, M. (1987), Personal Communication.

Note 2: Comments arising f i ~ m a conversation with D. Elliott and D. Goodman 1987.

Note 3: Comments arising from a discussion involving the author, I.M. Franks, R.B.

Wilberg, and D. Goodman, 26th February, 1988.

Note 4: Ideas arising from a conversation with R. Lonergan, April, 1988.

Note 5: Bawa, P. (1988), Personal Communication.

Page 234: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

REFERENCES

Abend, W., Bizzi, E., & Morasso, P. (1982). Human arm trajectory formation. Brain, 105, 331-348.

Agarwal, G.C., & Gottlieb, G.L. (1984). Control theory and cybernetic aspects of motor systems. In H.T.A. Whiting (Ed.), Human motor actions: Bernstein reassessed. Amsterdam, North Holland.

Akelaitis, A.J. (1941). Studies on the corpus callosum 11: The higher visual functions in each homonymous field following complete section of the corpus callosum. Archives of Neurology and Psychiatry, 45,789-796.

Akelaitis, A.J. (1944). The study of gnosis, praxis and language following section of the corpus callosum and anterior commissure. Journal of Neurosurgery, l,94- 102.

Allen, M. (1983). Models of hemispheric specialization. Psychological Bulletin, 93,73- 104.

Allport, D.A. (1980). Patterns and actions: Cognitive mechanisms are content specific. In G.L. Claxton (Ed.), Co,onitive psychology: New directions. London: Routledge and Kegan Paul.

Amaducci, L., Sorbi, S., Albanese, A., & Gainotti, G. (198 1). Choline-acetyl transferase (CHAT) activity differs in right and left human temporal lobes. Neurology, 31, 799-805.

Annett, J., Annett, M., Hudson, P.T.W., & Turner, A. (1979). The control of movement in the preferred and non-preferred hands. Quarterly Journal of Experimental Psychology, 3 1, 641-652.

Annett, J., Golby, C.W., & Kay, H. (1958). The measurement of elements in an assembly task: The infoxmation output of the human motor system. Quarterly Journal of Experimental Psychology, 20, 1 - 1 1.

Annett, M. (1970a). A classification of handedness by association analysis. British Journal of Psychology, 6 1, 303-321.

Annett, M. (1985). Left, right, hand and brain: The right shift theory. New York: Erlbaum.

Anzola, G., Bertoloni, G,, Buchtel, H.A., & Rizzolatti, G. (1977). Spatial compatibility and anatomical factors in simple and choice reaction time. Neuropsychologia, 15, 295-305.

Anzola, G.P., Pulimeno, R., & Rizzolatti, G. (1980). Interserenza selettiva di un conpito motorio sui tempi di reazone a stimoli presentali nell'emicampo visivo di sinistra. Societa Italiano di Biologia Sperimentale, 56 (14), 1440-1444.

Atkinson, J., & Egeth, H. (1973). Right hemisphere superiority in visual orientation matching. Canadian Journal of Psychology, 27, 152- 158.

Bahrick, H.P., & Shelley, C. (1958). Time sharing as an index of automation. Journal of Experimental Psychology, 56,288-293.

Page 235: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Baer, D.J., & van der Kleij, P.CM (1978). Development of lateral asymmetries in the perception of sequentially touched fingers. Acta Psychologica, 42,357-365.

Bakan, D. (1966). The test of significance in psychological research. Psychological Bulletin, 66, 423-437.

Barlow, H. (1979). Reconstructing the visual image in space and time. Nature (London), 279, 189-190.

Barnsley , R.H., & Rabinovitch, M. (1970). Handedness: Proficiency versus stated preference. Perceptual and Motor Skills, 30,343-362.

Barr, M.L., & Kiernan, J.A. (1983). The human nervous system: An anatomical viewpoint. Philadelphia: Harper and Row.

Bashore, T.R. (1981). Vocal and manual reaction time estimates of interhemispheric transmission time. Psychological Bulletin, 89,352-368.

Beaton, A.A. (1979). Hemispheric function and dual task performance. Neuropsychologia, 17, 629-635.

Beaubaton, D., & Hay, L. (1986). Contribution of visual information to feedforward and feedback processes in rapid pointing movements. Human Movement Sciences, 5, 19-34.

Beggs, W.D.A., & Howarth, C.I. (1970). Movement control in a repetitive motor task. Nature, 225,752-753.

Benton, A.L. (1969). Disorders of spatial orientation. In P.J. Vinken & G.W. Bruyn (Eds.), Symposium on Fatigue, 3,212-228. Amsterdam, North Holland.

Benton, A.L., & Hecaen, H. (1970). Stereoscopic vision in patients with unilateral cerebral disease. Neurology, 20, 1084-1088.

Benton, A.L., Meyers, R., & Polder, G.T. (1962). Some aspects of handedness. Psychiatria et Neurologia, 144, 321-337.

Berlucchi, G., Heron, W., Hyman, R., Rizzolatti, G., & Umilta, C. (1971). Simple reaction times of ipsilateral and contralateral hand to lateralized visual stimuli. Brain, 94,419-430.

Bernstein, N. (1 984). Biodynamics of locomotion. In H.T. A. Whiting (Ed.), Human motor action: Bemstein reassessed. Amsterdam, North Holland

Bertelson, P. (1981). The nature of hemispheric specialization: Why should there be a common principle? The Behavioral and Brain Sciences, 4,63-64.

Biguer, B., Jeannerod, M., & Prablanc, C. (1982). The coordination of eye, head and arm movements during reaching at a single visual target. Experimental Brain Research, 46, 301-304.

Page 236: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Bogen, J.E. (1969a). The other side of the brain I. Dysgraphia and dyscopia following cerebral commissurotomy . Bulletin of the Los Angeles Neurological Society , 34, 73- 105.

Bogen, J.E. & Gazzaniga, M.S. (1965). Cerebral cornmissurotomy in man. Minor hemisphere dominance for certain visuo spatial functions. Journal of Neurosurg., 23, 394-399.

Boll, T.J. (1974). Right and left cerebral hemisphere damage and tactile perception: Performance of the ipsilateral and contralateral sides of the body. Neuropsychologia, 12,235-238.

Boring, E.G. (1950). A history of experimental psychology. New York: Appleton- Century-Crofts.

Bower, G.H. (1972). Mental imagery and associative learning. In L. Gregg (Ed.), Cognition in learning and memory. New York: John Wiley & Sons.

Bowers, D., Heilman, K., Satz, P., & Altman, A. (1978). Simultaneous performance on verbal, nonverbal and motor tasks by right handed adults. Cortex, 14,540-556.

Bradshaw, J.L., & Nettleton, N.C. (1981). The nature of hemispheric specialization in man. The Behavioral and Brain Sciences, 4,51-91.

Brebner, J., Shephard, M., & Cairney, P. (1972). Spatial relationships and S-R compatibility. Acta Psychol, 36, 1-15.

Bresard, B., & Bresson, F. (1987). Reaching or manipulation: Left or right? Behavioral and Brain Sciences, 10,265-266.

Brindley, G.S., & Merton, P.A. (1960). The absence of position sense in the human eye. Journal of Physiology, 153, 127- 130.

Brinkman, J., & Kuypers, H.G.J.M. (1973). Cerebral control of contralateral and ipsilateral arm, hand and finger movements in the split brain rhesus monkey. Brain, 96, 653-674.

Broca, P. (1861). Remarques sur la siege de la faculte du langage articule. Bulletin de la societe d'anthropologie (Paris), 6.

Brodie, D.A. (1984). The neuropsychology of dual task performance: A motor behavior analysis. Unpublished doctoral dissertation, University of Michigan, Ann Arbor, Michigan.

Brooks, B.A., & Fuchs, A.F. (1975). Influence of stimulus parameters on visual sensitivity during saccadic eye movement. Vision Research, 15, 13 89- 1398.

Brooks, V.B. (1974). Some examples of programmed limb movements. Brain Research, 71, 299-308.

Brouchon-Viton, M., & Jordan, P. (1978). Relevant cues in visuo-motor rearrangement. Neurosci. Lett. Suppl. 1 :S.386.

Page 237: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Brown, S.H., & Cooke, J.D. (1981). EMG responses to force perturbations preceding accurate arm movements in humans. Neuroscience Abstracts, 7,477.

Bryden, M.P. (1965). Tachistoscopic recognition, handedness, and cerebral dominance. Neuropsychologia, 3, 1-8.

Bryden, M.P. (1976). Response bias and hemispheric differences in dot localization. Perception and Psychophysics, 19,23-28.

Bryden, M.P. (1982). Laterality: Functional asymmetry in the intact brain. New York: Academic Press.

Bullock, T.H. (1965). Physiological bases of behavior. In J.A. Moore (Ed.), Ideas in modem biology. New York: Natural History Press.

Carlton, L.G. (1979). Control processes in the production of discrete aiming responses. Journal of Human Movement Studies, 5, 1 15- 124.

Carlton, L.G. (1981a). Processing visual information for motor control. Journal of Experimental Psychology: Human Perception and Performance, 7,10 19- 1030.

Carlton, L.G. (1981b). Visual information: The control of aiming movements. Quarterly Journal of Experimental Psychology, 33A, 87-93.

Cannon, A., & Bechtoldt, H.P. (1969). Dominance of the right cerebral hemisphere for stereopsis. Neuropsyc hologia, 7, 29-39.

Cannon, A., & Benton, A.L. (1969). Tactile perception of direction and number on patients with unilateral cerebral disease. Neurology, 19, 525-532.

Carmon, A., & Benton, A.L. (197 1). Tactile perception of direction in relation to hemispheric locus of lesion. Neuropsychologia, 9,83-88.

Carson, R.G. (1987a, June). Manual asymmetries: Feedback processing, output variability and spatial complexity. A review. Paper presented at the conference of the North American Society for the Psychology of Sport and Physical Activity, Vancouver, B .C.

Carson, R.G. (1987b, October). Motor recognition processes: Do we structure the memory set? Paper presented at the conference of the Canadian Psychomotor Learning and Sport Psychology, Banff, Alberta.

Churchland, P.S . (1986). Neurophilosophy: Toward a unified science of the mind-brain. Cambridge, M.A.: MIT Press.

Cohen, G. (1973). Hemispheric differences in serial versus parallel processing. Journal of Experimental Psychology, 97,349-356.

Cohen, G. (198 1). Explaining hemispheric asymmetry: New dichotomies for old. The Behavioral and Brain Sciences, 4,67.

Connolly, C.J. (1950). External morphology of the primate brain. Springfield, Ill.: Charles C. Thomas.

Page 238: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Conti, P., & Beaubaton, D. (1976). Utilisation des informations visuelles dans le controle du movement: Etude de la precision des pointage chez l'homme. Travail. Humain, 39, 19-32.

Cooke, J.D., & Diggles, V.A. (1984). Rapid error correction during human arm movements: Evidence for central monitoring. Journal of Motor Behavior, 16,348- 363.

Cooper, L.A. (1973). Chronometric studies of the rotation of menatl images. In W.G. Chase, (Ed.), Visual Infomation Processing. New York: Academic Press.

Corballis, M.C. (1981). Toward an evolutionary perspective on hemispheric specialization. The Behavioral and Brain Sciences, 4,69-70.

Cotton, B., Tzeng, O.J.L., & Hardyck, C. (1980). Role of cerebral hemispheric processing in the visual half field stimulus-response compatibility effect. Journal of Experimental Psychology: Human Perception and Performance, 6, 13-23.

Critchley, M. (1953). The parietal lobes. London: Arnold.

Critchley, M., & Henson, R.A. (1977). Music and the brain: Studies in the neurology of music. London: Heinemann.

Crossman, E.R.F.W., & Goodeve, P.J. (1963). Feedback control of hand movement and Fitts' law. Proceedings of the Experimental Society, Oxford.

Damasio, A.R., & Geschwind, N. (1984). The neural basis of language. Annu. Rev. Neurosci., 7, 127- 147.

Danly, M., & Shapiro, B. (1982). Speech prosody in Broca's aphasia. Brain and Language, 16, 171-190.

Davis, A.E., & Wada, J.A. (1977). Hemispheric asymmetries of visual and auditory information processing. Neuropsychologia, 15,799-806.

Dejerine, J. (1891). Sur un cas de cecite verbale avec a graphie, suivi d'autopsie. Mem. Soc. Biol., 3, 197-201.

Dejerine, J., & Thomas, A. (19 12). Contribution a l'etude de l'aphasie chez les gauchers. Rev. Neurol., 24, 213-226.

De Renzi, E. (1967, October). Asimmeme emisferiche nella rappresentazione di talune funzioni nervose superior non verbali. Atti del XVI Congresso Nazionale di Neurologia, Rome, 1, 37 1-430.

De Renzi, E. (1978). Hemispheric asymmetry as evidenced by spatial disorders. In M. Kinsbourne (Ed.), Asymmetrical function of the brain. Cambridge: Cambridge University Press.

De Renzi, E., Faglioni, P., & Previdi, P. (1977). Spatial memory and hemispheric locus of lesion. Cortex, 13,424-433.

De Renzi, E., Faglioni, P., & Scotti, G. (1970). Hemispheric contribution to exploration of space through visual and tactile modality. Cortex, 6, 191-203.

2 2 4

Page 239: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

De Renzi, E., & Nichelli, P. (1975). Verbal and nonverbal short term memory impairment following hemisphere damage. Cortex, 1 1,341-353.

De Renzi, E., Scotti, G., & Spinnler, H. (1969). Perceptual and associative disorders of visual recognition. Neurology, 19,634-642.

De Renzi, E., & Spinnler, H. (1966). Visual recognition in patients with unilateral cerebral disease. J. Nerv. Ment. Dis., 142, 515-525.

de Schonon, S., & Bresson, F. (1984). Developpement de l'atteinte manuelle d'un object chez l'enfant. In J. Paillard (Ed.), La lecture sensorimomce et cognitive de l'experience spatiale. Paris: Centre National de la Recherche Scientifique.

Dewhurst, D.J. (1967). Neuromuscular control system. IEEE Transactions on Bio- Medical Engineering, 14, 167.

Diamond, S.J., & Beaumont, J.G. (1972b). Processing in perceptual integration between and within the cerebral hemispheres. British Journal of Psychology, 63, 509-514.

Di S tefano, M., Morelli, M., Mani, C.A., & Berlucchi, G. (1980). Hemispheric control of unilateral and bilateral movements of proximal and distal parts of the arms as inferred from simple reaction time to lateralized light stimuli in man. Experimental Brain Research, 38, 197-204.

Dome, T., & Todor, J.I. (1978). Motor ability as a function of handedness. In D.M. Landers & R.W. Christina (Eds.), Psychology of Motor Behavior and Sport (pp.264-27 1). Champaign, IL. : Human Kinetics.

Dodds, A.G. (1978). Hemispheric differences in tactuo-spatial processing. Neuropsychologia, 16, 147-250.

Dreyfus, H.L. (1979). What computers can't do: The limits of artificial intelligence. New York: Harper and Row.

Dumford, M., & Kimura, D. (197 1). Right hemisphere specialisation for depth perception reflected in visual field differences. Nature, 231, 394-395.

Eals, M. (1987). Asymmetric processing in perception of apparent movement. Neuropsychologia, 25,429-434.

Eccles, J.C. (1967). Circuits in the cerebellar control of movement. Proc. nat. Acad. Sci. (Wash.), 58, 336-343.

Egeth, H. (1971). Laterality effects in perceptual matching. Perception and Psychophysics, 9, 375-376.

Erickson, T.C. (1940). Spread of epileptic discharge. Archives of Neurology and Psychiatry, 43,429-452.

Evarts, E.V. (1973). Motor cortex reflexes associated with learned movements. Science, 179, 501-503.

Page 240: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Faglioni, P., & Basso, A. (1985). Historical perspectives on neuroanatomical correlates of limb apraxia. In E.A. Roy (Ed.), Neuropsychological studies of apraxia and related disorders. Elsevier, North Holland.

Festinger, L., & Canon, L.K. (1965). Information about spatial location based on knowledge about efference. Psychological Review, 72,373-384.

Fisk, J.D., & Goodale, M.A. (.1985). The organization of eye and limb movements during unrestricted reaching to targets in contralateral and ipsilateral visual space. Experimental Brain Research, 60, 159- 178.

Fitts, P.M. (1954). The information capacity of the human motor system controlling the amplitude of movements. Journal of Experimental Psychology, 47,38 1-39 1.

Flowers, K. (1975). Handedness and controlled movement. British Journal of Psychology, 66, 39-52.

Fontenot, D.J., & Benton, A.L. (1971). Tactile perception of direction in relation to hemispheric locus of lesion. Neuropsychologia, 9,83-88.

Franco, L., & Sperry, R.W. (1977). Hemisphere lateralization for cognitive processing of geometry. Neuropsychologia, 15, 107- 1 1 1.

French, J.W. (1951). The description of aptitude and achievement tests in terms of rotated factors. Psychometric Monogr., NOS.

Freyd, J.J. (1983). The mental representation of movement when static stimuli are viewed. Perception and Psychophysics, 33,575-58 1.

Friedman, A., & Polson, M.C. (1981). Hemispheres and independent resource systems: Limited capacity processing and cerebral specialization. Journal of Experimental ~s~chology: HU&UI perception and performance, 7, 103 1 - 105 8.

Gainotti, G., & Tiacci, G. (1971). The relationship between disorders of visual perception and unilateral spatial neglect. Neuropsychologia, 9,45 1-458.

Galaburda, A.M., & Sanides, V.F. (1980). Cytoarchitectonic organization of the human auditory cortex. Journal of Comparitive Neurology, 190,597-6 10.

Galaburda, A.M., Sanides, F., & Geschwind, N. (1978). Human brain: Cytoarchitectonic left right asymmetries in the temporal speech region. Archives of Neurology, 35, 812-817.

Galin, D., & Ellis, R.R. (1975). Asymmetry in evoked potentials as an index of lateralized cognitive processes: Relation to EEG alpha asymmetry. Psychophysiology, 13, 45-50.

Galin, D., & Ornstein, R. (1972). Lateral specialization of cognitive mode: An EEG study. Psychophysiology, 9 , 4 12-41 8.

Gardiner, G., Franks, I.M., & Goodman, D. (1987). A microcomputer based tracking task for examination of the spatial and temporal organization of perceptual motor skill. Behavior Research Methods, Instruments and Computers, 19,361-364.

Page 241: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Gardner, H. (1985). The mind's new science. New York: Basic Books.

Gazzaniga, M.S. (1970). The bisected brain. New York: Appleton Century Crofts.

Geffen, G., Bradshaw, J.L., & Nettleton, N.C. (1972). Hemispheric asymmetry: Verbal and spatial encoding of visual stimuli. Journal of Experimental Psychology, 95, 25-3 1.

Geffen, G., Bradshaw, J.L., & Wallace, G. (1971). Interhemispheric effects on reaction time to verbal and non-verbal stimuli. Journal of Experimental Psychology, 87, 4 15-422.

Georgopoulos, A.P., Kalaska, J.F., & Massey, J.T. (1981). Spatial trajectories and reaction times of aimed movements: effects of practice, uncertainty, and change in target location. Journal of Neurophysiol., 46,725-743.

Geschwind, N. (1974). The anatomical basis of hemispheric differentiation. In S.J. Dimond & J.G. Beaumont (Eds.), Hemisphere function in the human brain. New York: John Wiley & Son.

Geschwind, N., & Levitsky, W. (1968). Human brain: Left-right asymmetries in temporal speech region. Science, 161, 186- 187.

Gibson, A.R., Filbey, R., & Gazzaniga, M.S. (1970). Hemisphere differences as reflected by reaction time. Fed. Proc., 29, 658.

Gibson, J.J. (1950). The perception of the visual world. Boston: Houghton Mifflin.

Gibson, J.J. (1966). The senses considered as perceptual systems. Boston: Houghton- Mifflin.

Giezen, C.C.D.M., van den Heuvel, P. J.M., & Gon, J.J. Denier van der. (1984). Modification of muscle activation patterns during fast goal directed arm movements. Journal of Motor Behavior, 16,2- 18.

Glencross, D.J. (1977). Control of skilled movements. Psychol. Bulletin, 84, 14-29.

Glezer, 1.1. The riddle of Carlyle: The unsolved problem of the origin of handedness. Behavioral and Brain Sciences, 10,273-275.

Goldstein, K. (1917). Die transtatitalen aphasien. Jena: Gustav Fischer.

Goodale, M.A. (1987). Two hemispheres: One reaching hand Behavioral and Brain Sciences, 10, 275-276.

Gott, P.S. (1973a). Cognitive abilities following right and left hemispherectomy. Cortex, 9, 266-274.

Granit, R. (1972). Constant errors in the execution and appreciation of movement. Brain, 95, 649-660.

Grant, D.A. (1962). Testing the null hypothesis and the strategy and tactics of investigating theoretical models. Psychological Review, 69,54-6 1.

Page 242: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Greene, P.H. (1972). Problems of organization of motor systems. In R. Rosen & F. Snell (Eds.), Progress in theoretical biology (Vo1.2). New York: Academic Press.

Grillner, S., & Zangger, P. (1979). On the central generation of locomotion in the low spinal cat. Experimental Brain Research, 34,241-262.

Grusser, O.J. (1986). The multirnodal structure of extrapersonal space. In A. Hein & M. Jeamerod (Eds.), Spatially oriented be haviour. New York: Springer.

Guiard, Y. (1987). Precursors to what? Theory is lacking for handedness in humans. Behavioral and Brain Sciences, 10,276-277.

Guiard, Y., Diaz, D., & Beaubaton, D. (1983). Left hand advantage for right handers for spatial constant error: Preliminary evidence in a unimanual ballistic aimed movement. Neuropyschologia, 2 1, 1 1 1- 1 15.

Guildford, J.P. (1947). Printed classification tests. AFF report no.5. Washington, D.C.: GPO.

Hallett, M., Shahani, B.T., & Young, R.A. (1975). EMG analysis of stereotyped voluntary movements in man. Journal of Neurology, Neurosurgery, and Psychiatry, 38, 1154-1161.

Hammond, G.R. (1982). Hemispheric differences in temporal resolution. Brain and Cognition, 1,95- 118.

Hannay, H.J., Varney, N.R., & Benton, A.L. (1976). Visual localization in patients with unilateral brain disease. Journal of Neurology, Neurosurgery, and Psychiatry, 39, 307-313.

Harris, L.J. (1978). Sex differences in spatial ability: Possible environmental, genetic, and neurological factors. In M. Kinsbourne (Ed.), Asymmetrical function of the brain. Cambridge: Cambridge University Press.

Harris, L.J. (1980). Which hand is the 'eye' of the blind? A new look at an old question. In J. Herron (Ed.), Neuropsychology of left-handedness (pp.303-329). New York: Academic Press.

Harris, L.J., & Can, T.H. (1981). Implications of differences between perceptual systems for the analysis of hemispheric specialization. Behavioral and Brain Sciences, 4, 7 1-72.

Hary, D., & Moore, G.P. (1985). Temporal tracking and synchronization strategies. Human Neurobiology, 4, 73-76.

Hecaen, H., & Albert, M. (1978). Human neuropsychology. New York, N.Y.: John Wiley & Son.

Heilman, K.M., Scholes, R., & Watson, R.T. (1975). Auditory affective agnosia: Disturbed comprehension of affective speech. JournJ of Neurology, Neurosurgery, and Psychiatry, 38, 69-72.

Hellige, J.B., & Longstreth, L.E. (198 1). Effects of concurrent hemisphere-specific activities on unirnanual tapping rate. Neuropsychologia, 19,395-405.

2 2 8

Page 243: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Hermelin, B., & O'Connor, N. (1971). Functional asymmetry in the reading of braille. Neuropsychologia, 9, 43 1-435.

Heuer, H. (1987). Does a hand preference indicate a hemispheric specialization? Behavioral and Brain Sciences, 10,277-278.

Hicks, R.E., Provenzani, F.J.; & Rubstein, E.D. (1975). Generalized and lateralized effects of concurrent verbal rehearsal upon performance of sequential movements of the fingers by the left and right hands. Acta Psychologica, 39, 119- 130.

Honda, H. (1981). Eye movements and performance during bilateral tracing tasks. Acta Psychologica, 49, 201-213.

Honda, H. (1982). Rightward superiority of eye movements in a bimanual aiming task. Quarterly Journal of Experimental Psychology, 34A, 499-5 13.

Honda, H. (1984). Functional between-hand differences and outflow eye position information. Quarterly Journal of Experimental Psychology, 36A, 75-8 8.

Howarth, C.I., Beggs, W.D.A., & Bowden, J.M. (1971). The relationship between speed and accuracy of movements aimed at a target. Acta Psychologica, 35,207-218.

Ikeda, K (1987). Lateralized interference effects of concurrent verbal tasks on sequential finger tapping. Neuropsychologia, 25,453-456.

Jankelevitc h, V. (1 977). La musique et l'inneffable. Paris: Armand Collin.

Jeannerod, M., & Biguer, B. (1982). Visuomotor mechanisms in reaching within extrapersonal space. In D. Ingle, M.A. Goodale, & R.J.W. Mansfield (Eds.), Analysis of visual behaviour. Cambridge, MA: M.I.T. Press.

Jeannerod, M., & Prablanc, C. (1983). Visual control of reaching movements in man. In J.E. Desmedt (Ed.), Motor control mechanisms in health and disease. New York: Raven Press.

Jeeves, M.A. (1970). A comparison of interhemispheric transfer times in acallosals and normals. Psychonomic Science, 16,245-246.

Jeeves, M.A., & Dixon, N.F. (1970). Hemispheric differences in response rates to visual stimuli. Psychonomic Science, 20,249-25 1.

Kahneman, D. (1973). Attention and effort. Englewood Cliffs, N.J.: Prentice Hall, Inc.

Kay, B.A., Kelso, J.A.S., Saltzman, E.L., & Schoner, G. (1987). Space-time behaviour of single and bimanual rhythmical movements: Data and limit cycle model. Journal of Experimental Psychology: Human Perception and Performance, 13,178-192.

Keele, S .W. (1968). Movement control in skilled motor performance. Psychological Bulletin, 70, 387-403.

Keele, S.W., & Posner, M.I. (1968). Processing of visual feedback in rapid movements. Journal of Experimental Psychology, 77, 1%- 158.

Page 244: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Kim, Y., Royet, F., Bonstelle, C., & Boller, F. (1980). Temporal sequencing of verbal and nonverbal materials: The effect of laterality of lesion. Cortex, 16, 135-143.

Kimura, D. (1961). Cerebral dominance and the perception of verbal stimuli. Canadian Journal of Psychology, 15, 166-171.

Kimura, D. (1963). Right temporal lobe damage. Arch. Neurol., 8,264-27 1.

Kimura, D. (1966). Dual functional asymmetry of the brain in visual perception. Neuropsychologia, 4, 275-285.

Kimura, D. (1969). Spatial localization in left and right visual fields. Canadian Journal of Psychology, 23,445-458.

Kimura, D. (1977). Acquisition of a motor skill after left hemisphere damage. Brain, 100, 527-542.

Kimura, D. (1979). Neuromotor mechanisms in the evolution of human communication. In H.D. Steklis & M.J. Raleigh (Eds.), Neurobiology of social communication in primates: An evolutionary perspective. New York: Academic Press.

Kimura, D., & Archibald, Y. (1974). Motor functions of the left hemisphere. Brain, 97, 337-350.

Kimura, D., & Davidson, W. (1975). Right a m superiority for tapping with distal and proximal joints. Journal of Human Movement Studies, 1, 199-202.

Kimura, D., & Durnford, M. (1974). Normal studies on the function of the right hemisphere in vision. In S.J. Dirnond & J.G. Beaumont (Eds.), Hemispheric function in the human brain. New York: John Wiley & Son.

Kinsbourne, M. (1970). The cerebral basis of lateral asymmetries in attention. Acta Psychologica, 33, 193-201.

Kinsbourne, M. (1974a). Lateral interactions in the brain. In M. Kinsbourne & W.L. Smith (Eds.), Hemisphere disconnection and cerebral function. Springfield, Ill.: Charles C. Thomas.

Kinsbourne, M. (1974b). Mechanisms of hemispheric interaction in man. In M. Kinsbourne & W.L. Smith (Eds.), Hemisphere disconnection and cerebral function. Springfield, Ill.: Charles C. Thomas.

Kinsbourne, M. (1978). Biological determinants of functional bisymmetry and asymmetry. In M. Kinsbourne (Ed.), Asymmetrical function of the brain. Cambridge: Cambridge University Press.

Kinsbourne, M., & Cook, J. (1971). Generalized and lateralized effects of concurrent verbalization on a unimanual skill. Quarterly Journal of Exp. Psychology, 23, 341-345.

Kinsbourne, M., & Hicks, R.E. (1978). Functional cerebral space: A model for overflow, transfer and interference effects in human performance: a tutorial review. In J. Requin (Ed.), Attention and performance VII (pp.345-362). Hillsdale, N.J.: Lawrence Erlbaum.

230

Page 245: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Klatzky, R.L. (1970). Interhemispheric transfer of test stimulus representations in memory scanning. Psychonomic Science, 2 1,20 1-203.

Kohn, B., & Dennis, M. (1974). Selective impairments of visuo-spatial abilities in infantile hemiplegics after right cerebral hemidecortication. Neuropsychologia, 12,505- 512.

Kristeva, R., Keller, E., Deecke, L., & Kornhuber, H.H. (1979). Cerebral potentials preceding unilateral and simultaneous bilateral finger movements. Electroencephalography and Clinical Neurophysiology, 47,229-23 8.

Kugler, P.N., Kelso, J.A.S., & Turvey, M.T. (1982). On the control of naturally developing systems. In J.A.S. Kelso & J.E. Clark (Eds.), The Development of Movement Control and Coordination, Chichester Wiley.

Kuypers, H.G.J.M. (1978). From motor control to conscious experience. In Buser and Rouged Buser (Eds.), Cerebral correlates of conscious experience. INSERM Symposium No.6,95- 110. Elsevier, North Holland: Biomedical Press.

Kuypers, H.G.J.M. (1981). Anatomy of the descending pathways. In V.E. Brooks (Ed.), Handbook of physiology ; Sec.1, The nervous system, Vo12: motor control (part2). American Physiological Society.

Kuypers, H.G.J.M. (1984, February). Brain systems providing motor control. Paper presented at the International Neuropsychological Society, Houston, Texas.

Ladavas, E. (1987). Influence of handedness on spatial compatibility effects with perpendicular arrangement of stimuli and responses. Acta Psychologica, 64,13- 23

La Grone, C.W., Jr. (1942). An experimental study of the relationship of peripheral perception to factors in reading. Journal of Experimental Education, 11, 37-49.

Lansdell, H.C. (1961). Two selective deficits found to be lateralized in temporal neurosurgery patients. Paper presented to the 32nd annual meeting of the Eastern Psychological Association, Philadelphia.

Lansdell, H. (1968). Effect of extent of temporal lobe ablations on two lateralized deficits. Physiol. Behavior, 3, 27 1-273.

Lashley, K.S. (1950). In search of the engram. Symposium of the Society of Experimental Biology, 4,454-482.

Lawrence, D.G., & Hopkins, D.A. (1976). The development of motor control in the rhesus monkey: Evidence concerning the role of corticoneuronal connections. Brain, 99,235-254.

Lawrence, D.G., & Kuypers, H.G.J.M. (1968a). The functional organization of the motor system in monkey. I. The effects of pyramidal lesions. Brain, 9 1, 1- 14.

LeDoux, J.E., Wilson, D.H., & Gazzaniga, M.S. (1977). Manipulo-spatial aspects of cerebral lateralization. Clues to the origin of lateralization. Neuropsychologia, 15, 743-750.

23 1

Page 246: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Lee, D.N. (1980). Visuo-motor coordination in space-time. In G.E. Stelmach & J. Requin (Eds.). Tutorials in Motor Behavior. Amsterdam, North Holland.

Lee, D.N., & Thomson, J.A. (1982). Vision in action: The control of locomotion. In D. Ingle, M.A. Goodale, & R.J.W. Mansfield (Eds.), Analysis of visual behaviour. Cambridge, MA: M.I.T. Press.

Lee, R.G., Lucier, G.E., & white, . (1981). Modification of motor output to compensate for unexpected load conditions during ballistic movements. Neuroscience Abstracts, 7, 477.

LeMay, M., & Culebras, A. (1972). Human brain - morphologic differences in the hemisphere demonstrable by carotid anteriography. The New England Journal of Medicine, 287, 168-170.

LeMay, M., & Geschwind, N. (1978). Asymmetries of the human cerebral hemispheres. In A. Caramazza & E. Zurif (Eds.), Language acquisition and language breakdown. Baltimore: John Hopkins University Press.

Levy-Agresti, J., & Sperry, R.W. (1968). Differential perceptual capacities in major and minor hemispheres. Proc. U.S. Nat. Acad. Sci., 61, 1 15 1.

Levy, J. (1969). Possible basis for the evolution of lateral specialization in the human brain. Nature, 224, 6 14-6 15.

Lomas, J. (1980). competition within the left hemisphere between speaking and unimanual tasks performed without visual guidance. Neuropsychologia, 1 8, 14 1 - 149.

Lomas, J., & Kimura, D. (1976). Intrahemispheric interaction between speaking and sequential manual activity. Neuropsychologia, 14,23-33.

Longden, K., Ellis, C., & Iverson, D.S. (1976). Hemispheric differences in the discrimination of curvature. Neuropsychologia, 14, 195-202.

Luria, A.R. (1970). Traumatic aphasia. The Hague: Mouton.

Mackay, D.M. (1970). Elevation of visual threshold by displacement of retinal image. Nature, 275, 766-768.

MacKenzie, C.L., Sivak, B., & Elliott, D. (in press). Manual localization of lateralized visual targets. Journal of Motor Behavior.

MacNeilage, P.F., Studdert-Kennedy, M.G., & Lindblom, B. (1987). Primate Handedness reconsidered. Behavioral and Brain Sciences, 10,247-303.

Marin, O.S.M. (1976). Neurobiology of language: An overview. Annals of the New York Academy of Sciences, 280,900-912.

Marshall, J.C. (198 1). Hemispheric specialization: What, how and why. The Behavioral and Brain Sciences, 4,72-73.

Marteniuk, R.G., Leavitt, J., & MacKenzie, C. (1987, June). Characteristics of human arm and hand coordination. Paper presented at the Conference on Robotics and

2 3 2

Page 247: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Motor Control: Corrrmonalities and Differences, Simon Fraser University, Burnaby, B.C.

Mateer, C., & Kimura, D. (1977). Impairment of nonverbal oral movements in aphasia. Brain and Language, 4,262-276.

Mather, J.A., & Fisk, J.D. (1985). Orienting to targets by looking and pointing. I. Parallels and interactions in ocular and manual performance. Quarterly Journal of Experimental Psychology, 37A, 3 15-338.

Matin, L. (1982). Visual localization and eye movements. In A.H. Wertheim, A.W. Leibowitz, & A.W. Wagenaar (Eds.), Tutorials on motor perception. New York: Plenum Press.

Mazziotta, J.C., & Phelps, M.E. (1983). Human neuropsychological imaging studies of local brain metabolism and blood flow: Strategies and results. Archives of Neurology Abstracts, 40,767.

McCullough, W. (1940). Cited in R.W. Sperry (1964), The great cerebral commissure. Scientific American, 210 (I), 42-52.

McFarland, K., & Ashton, R. (1978a). The influence of brain lateralization of function as a manual skill. Cortex, 14, 102-1 11

McFarland, K., & Ashton, R. (1978b). The lateralized effects of concurrent cognitive and motor performance. Perception and Psychophysics, 23,344-349.

McFie, J., & Piercy, M.F. (1952). Intellectual impairment with localized cerebral lesions. Brain, 75, 292-3 1 1.

McKeever, W.F. (1981). On laterality research and dichotornania. The Behavioral and Brain Sciences, 4,73-74.

McRae, D.L., Branch, C.L., & Milner, B. (1968). The occipital horns and cerebral dominance. Neurology, 18,95-98.

Meehl, P.E. (1967). Theory-testing in psychology and physics: A methodological paradox. Philosophy of Science, 34, 103-1 15.

Megan, E.D. (1974). Possible modification to a rapid ongoing programmed manual response. Brain Research, 7 1,425-441.

Meier, M.J., & French, L.A. (1965). Lateralized deficits in complex visual discrimination and bilateral transfer of reminiscence following unilateral temporal lobectomy. Neuropsychologia, 3, 26 1-272.

Mendela, J. (1972). A comment on Meehl's Paradox. The Psychological Record, 22,375- 376.

Merleau-Ponty, M. (1962). Phenomenology of Perception. London: Routledge and Kegan Paul.

Metzger, R.L., & Antes, J.R. (1976). Sex and coding strategy effects on reaction time to hemispheric probes. Memory and Cognition, 4, 167- 17 1.

233

Page 248: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Milner, B. (1958). Psychological deficits products by temporal lobe excision. Res. Publ. Ass. Res. Nerv. Ment. Dis., 36, 244-257.

Milner, B. (1971). Interhemispheric differences in the localization of psychological processes in man. British Medical Bulletin, 27,272-277.

Milner, B., & Teuber, H.L. (1968). Alteration of perception and memory in man: Reflections on methods. In L. Weiskrantz (Ed.), Analysis of behavioural change. New York: Harper and Row.

Morgan, M.J. (1980). Analogue models of motion perception. Philisophical transactions of the Royal Society of London, Series B-Biological Sciences, 290, 117-135.

Morgan, M.J. (1981). Hemispheric specialization and spatiotemporal interactions. The Behavioral and Brain Sciences, 4,74-75.

Morraso, P., & Tagliasco, V. (1986). Human movement understanding: from computational geometry to artificial intelligence. Amsterdam: North Holland

Moscovitch, M. (1979). Information processing and the cerebral hemispheres. In M.S. Gozzaniga (Ed.), Handbook of behavioral neurobiology, Vo1.2, neuropsychology. New York: Plenum.

Nachshon, I., & Cannon, A. (1975). Hand preference in sequential and spatial discrimination tasks. Corte x, 1 1, 123- 13 1.

Nebes, R.D. (197 1). Superiority of the minor hemisphere in comrnissurotomized man for the perception of part whole relations. Corte x, 7,333-349.

Nebes, R.D. (1972). Dominance of the minor hemisphere in commissurotomized man on a test of figural unification. Brain, 95,633-638.

Nebes, R.D. (1973). Perception of dot patterns by the disconnected right and left hemisphere in man. Neuropsychologia, 11,285-290.

Nebes, R.D. (1978). Direct examination of cognitive function in the right and left hemispheres. In M. Kinsbourne (Ed.), Asymmetrical function of the brain. Cambridge: Cambridge University Press.

Nottebohm, F. (1979). Origins and mechanisms in the establishment of cerebral dominance. In M.S. Gazzaniga (Ed.), Handbook of behavioural neurobiology, Vo1.2. New York: Plenum Press.

Nottebohm, F. (1981). Does hemispheric specialization of function reflect the needs of an executive side? The Behavioral and Brain Sciences, 4,75.

Ode, A., Keller, R., Mefford, I., & Adams, R.N. (1978). Lateralization of norepinephrine in the human thalamus. Science, 200, 141 1- 1413.

OMeld, R.C. (1971). The assessment and analysis of handedness: The edinburgh inventory. Neuropsychologia, 9,97- 1 13.

Page 249: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Paillard, J. (1971). Les determinants moteurs de l'organisation de l'espace. Cahiers Psychol., 14, 261-316.

Paillard, J. (1980). The multi channeling of visual cues and the organization of a visually guided response. In G.E. Stelmach & J. Requin (Eds.), Tutorials in motor behaviour. Amsterdam, North Holland.

Paillard, J. (1982). The contribution of peripheral and central vision to visually guided reaching. In D. Ingle, M.A. Goodale, & R.J.W. Mansfield (Eds.), Analysis of visual behaviour. Cambridge, MA: M.I.T. Press.

Paillard, J., & Brsuchon, M.A. (1974). A proprioceptive contribution to the spatial encoding of position cues for ballistic movements. Brain Research, 71,273-284.

Palmar, R.D. (1964). Development of differential handedness. Psychological Bulletin, 62, 257-272.

Papanicolaou, A.C., Schmidt, A.L., Moore, B.D., & Gisenberg, H.M. (1983). Cerebral activation patterns in an arithmetic and a visuospatial processing task. International Journal of Neuroscience, 20,283-288.

Paterson, A., & Zangwill, O.L. (1944). Disorders of visual space perception associated with lesions of the right cerebral hemisphere. Brain, 67,33 1-358.

Patterson, K., & Bradshaw, J.L. (1975). Differential hemispheric medication of nonverbal visual stimuli. Journal of Experimental Psychology: Human Perception and Performance, 1,246-252.

Pelisson, C., Prablanc, C., Goodale, M.A., & Jeannerod, M. (1986a). Visual control of reaching movements without vision of the limb. II. Evidence of fast unconscious processes correcting the trajectory of the hand to the final position of a double step stimulus. Experimental Brain Research, 62,303-3 1 1.

Pelisson, D., Prablanc, C., Goodale, M.A., & Jeannerod, M. (1986b). Visual control of reaching movements without vision of the limb. I. Experimental Brain Research, 62, 303-31 1.

Perenin, M.T., & Jeannerod, M. (1975). Residual vision in cortically blind hemifields. Neuropsychologia, 13, 1-7.

Perenin, M.T., & Jeannerod, M. (1978). Visual function within the hernianopic field following early cerebral hemidecortication in man. I. Spatial localization. Neuropsychologia, 16, 1 - 13.

Peters, M. (1976). Prolonged practice of a simple motor task by preferred and non- preferred hands. Perceptual and Motor Skills, 43,447-450.

Peters, M. (1980). Why the preferred hand taps more quickly than the non-preferred hand: Three experiments on handedness. Canadian Journal of Psychology, 34,62-7 1.

Peters, M. (1985). Constraints in the coordination of birnanual movement and their expression in skilled and unskilled subjects. Quarterly Journal of Experimental Psychology, 37A, 17 1- 196.

Page 250: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Peters, M. (1987). A nontrivial motor performance difference between right handers and left handers: Attention as intervening variable in the expression of handedness. Canadian Journal of Psychology, 41,91-99.

Peters, M., & Durding, B. (1978). Handedness as a continuous variable. Canadian Journal of Psychology, 32,257-261.

Peters, M., & Durding, B. (1979a). Left and right handers compared on a motor task. Journal of Motor Behavior, 1 1, 103- 1 1 1.

Pfeifer, R.A. (1936). Pathologie der horstrahlung und der corticalen horsphare. In 0. Bumke & 0. Foerster (Eds.), Handbuch der neurologie, Vol.VI. Berlin: Springer.

Poeck, K., & Huber, W. (1977). To what extent is language a sequential activity. Neuropsychologia, 15, 359-364.

Poeppel, E., Held, R., & Frost, D. (1973). Residual visual function after brain wounds involving the central visual pathways in man. Nature, 243,295-296.

Poffenberger, A.T. (1912). Reaction time to retinal stimulation with special reference to the time lost in conduction through nerve centers. Archives of Psychology, 23, 1-73.

Pohl, W., Butters, H., & Goodglass, H. (1972). Spatial discrimination and cerebral lateralization. Cortex, 8, 305-3 14.

Polich, J.M. (1978). Hemispheric differences in stimulus identification. Perception and Psychophysics, 24,49-57.

Prablanc, C., Echallier, J.F., Komillis, E., & Jeannerod, M. (1977). Optimal response of eye and hand motor systems in pointing. I. Spatio temporal characteristics of eye and hand movements and their relationships when varying the amount of visual information. Biological Cybernetics, 35, 1 13- 124.

Prablanc, C., Pelisson, D., & Goodale, M.A. (1986). Visual control of reaching movements without vision of the limb. I. Role of retinal feedback of target position in guiding the hand. Experimental Brain Research, 62,293-302.

Rashbass, C. (1961). The relationship between saccadic and smooth tracking eye movements. Journal of Physiology, 159,326-338.

Reed, E.S. (1982). An outline of a theory of action systems. Journal of Motor Behavior, 14, 98-134.

Requin, J., Semjen, A., & Bonnet, M. (1984). Bernstein's purposeful brain. In H.T.A. Whiting (Ed.), Human motor actions: Bernstein reassessed. Amsterdam, North Holland

Risberg, J., Halsey, J.H., Wills, E.L., & Wilson, E.M. (1975). Hemispheric specialization in normal man studied by bilateral measurements of the regional cerebral blood flow: A study with the 133 Xe inhalation technique. Brain, 98, 5 1 1-524.

Page 251: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Rizzolatti, G., Umilta, C., & Berlucchi, G. (1971). Opposite superiorities of the right and left cerebral hemispheres in discriminative reaction time to physiognomical and alphabetical material. Brain, 94,43 1-442.

Rodney, M.L. (1980). Motor sequencing and hemispheric specialization. Unpublished doctoral dissertation, University of Waterloo, Waterloo, Ontario.

Rorty, R. (1979). Philosophy and the mirror of nature. Princeton, N.J.: Princeton University Press.

Roy, E.A., & Elliott, D. (1986). Manual asymmetries in visually directed aiming. Canadian Journal of Psychology, 40, 109- 12 1.

Roy, E.A., & Elliott, D. (in press). Manual asymmetries in aimed movements. Quarterly Journal of Experimental Psychology.

Roy, E.A., & MacKenzie, C. (1978). Handedness effects in kinesthetic spatial location judgements. Cortex, 14, 250-258.

Rubino, C.A. (1970). Hemispheric lateralization of visual function. Cortex, 6, 102-120.

Satz. P.. Achenbach. K.. & Fennell. E. (1967). Correlations between assessed manual '

laterality andprehicted speech lateral& in a normal population. Neuropsychologia, 5, 295-310.

Scheerer, E. (1986). The constitution of space perception: A phenomenological perspective. Acta Psychologica, 63, 157- 173.

Schmidt, R.A. (1975. A schema theory of discrete motor skill learning. Psychological Review, 82, 225-260.

Schmidt, R.A. (1976). Control processes in motor skills. Exercise and Sports Sciences Reviews, 4, 229-261.

Schmidt, R.A. (1 982). Motor learning and control: A behavioural emphasis. Champaign, Ill: Human Kinetics.

Schmidt, R.A., Zelaznik, H.N., & Frank, J.S. (1978). Sources of inaccuracy in rapid movement. In G.E. Stelmach (Ed.), Information processing in motor control and learning. New York: Academic Press.

Schneider, G.E. (1969). Two visual systems. Science, 163, 895-902.

Seamon, J.G. (1974). Coding and Retrieval processes and the hemispheres of the brain. In S.J. Dimond & J.G. Beaumont (Eds.), Hemisphere function in the human brain. New York: John Wiley & Son.

Seamon, J.G., & Gazzaniga, M.S. (1973). Coding strategies and cerebral laterality effects. Cognitive Psychology, 5,249-256.

Searle, J. (1984). Minds, brains and science. Cambridge, MA: Harvard University Press.

Semmes, J. (1968). Hemispheric specialization: A possible clue to mechanism. Neuropsychologia, 6, 1 1-26.

Page 252: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Semmes, J., Weinstein, S., Ghent, L., & Teuber, H.L. (1963). Correlates of impaired orientation in personal and extrapersonal space. Brain, 86,742-772.

Serafetinides, E.A. (1965). The siWcance of the temporal lobes and of hemispheric dominance in the production of LSD-25 symptomatology in man. Neuropsychologia, 3, 69-79.

Sergent, J. (1982a). Influence of luminance on hemispheric processing. Bulletin of the Psychonomic Society, 20,221-223.

Sergent, J. (1982b). Basic determinants to visual-field effects with special reference to the Hannay et.al. (1981) study. Brain and Language, 16, 158-164.

Sergent, J. (1982~). Influence of the input characteristics on hemispheric cognitive processing. Unpublished doctoral dissertation, McGill University, Montreal, Quebec, Canada.

Sergent, J. (1982d). Methodological and theoretical consequences of variations in exposure duration in visual laterality studies. Perception and Psychophysics, 3 1,45 1-46 1.

Sergent, J. (1983a). Role of the input in visual hemispheric asymmetries. Psychological Bulletin, 93,481-512.

Sergent, J. (1983b). The effects of sensory limitations on hemispheric processing. Canadian Journal of Psychology, 37,345-366.

Simon, J.R., Hinrichs, J.V., & Craft, J.L. (1970). Auditory S-R compatibility: Reaction time as a function of ear-hand correspondence and ear-response-location comspondence. Journal of Experimental Psychology, 86,97- 102.

Sivak, B., Sivak, J.G., & MacKenzie, C.L. (1985). Contact lens design for lateralizing visual input. Neuropsychologia, 23,801-803.

Smith, A. (1966). Speech and other functions after left (dominant) hemispherectomy. J. Neurol. Neurosurg. Psychiatry, 29, 167- 17 1.

Smith, A. (1969). Nondominant Hemispherectomy. Neurology, 19,442-445.

Smith, W.M., & Bowen, K.F. (1980). The effects of delayed and displaced visual feedback on motor control. Journal of Motor Behavior, 12,9 1-101.

Smith, M.O., Chu, J., & Edmondston, W.E., Jr. (1977). Cerebral lateralization of haptic perception: Interaction of responses to braille and music reveals a functional basis. Science, 197, 689-690.

Sperling, G. (1960). The information available in brief visual presentations. Psychological Monographs, 74, (1 1, Whole No.498).

Sperry, R.W. (1964). The great cerebral cornmissure. Sci. Am., 210 (I), 42-52.

Sperry, R.W. (1974). Lateral specialisation in the surgically separated hemispheres. In F.O. Schmitt & F.G. Warden (Eds.), The neurosciences third study program. Cambridge, MA: M.I.T. Press.

2 3 8

Page 253: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Sperry, R.W. (1982). Some effects of disconnecting the cerebral hemispheres. Science, 217, 1223- 1226.

Springer, S.P., & Deutsch, G. (1985). Left brain, right brain. New York: Freeman.

Steingruber, H.L. (1975). Handedness as a function of task complexity. Perceptual and Motor Skills, 40, 263-266.

Summers, J.J., & Sharp, C.A. (1979). Bilateral effects of concurrent verbal and spatial rehearsal on complex motor sequencing. Neuropsychologia, 17, 331-343.

Sussman, H. (1971). The laterality effect in lingual auditory tracking. Journal of Acoustical Society of America, 49,1874- 1880.

Sussman, H. (1979). Evidence of left hemisphere superiority in processing movement related tonal signals. Journal of Speech and Hearing Research, 22,224-235.

Sussman, H., & MacNeilage, P.F. (1975). Studies of hemispheric specialization for speech production. Brain and Language, 2, 13 1 - 15 1.

Sussman, H., & Westbury, J.R. (1978). A laterality effect in isometric and isotonic labial tracking. Journal of Speech and Hearing Research, 21,563-579.

Tallal, P. (198 1). Temporal processing as related to hemispheric specialization for speech perception in normal and language impaired populations. The Behavioral and Brain Sciences, 4, 77-78.

Taylor, J. (1958). Selected writings of John Hughlings Jackson. New York: Basic Books.

Thornton, C.D., & Peters, M. (1982). Interference between concurrent speaking and sequential finger tapping: Both hands show a performance decrement under both visual and non visual guidance. Neuropsychologia, 20, 163- 169.

Thurstone, L.L. ( 1944). A factorial study of perception. Psychometric Monographs, No.4. Chicago: University of Chicago Press.

Thurstone, L.L. (1950). Some primary abilities in visual thinking. Report No. 59, Psychometric Laboratory. Chicago: University of Chicago Press.

Todor, J.I., & Cisneros, J. (1985). Accommodation to increased accuracy demands by the right and left hands. Journal of Motor Behavior, 17,355-372.

Todor, J.I., & Dome, T. (1978). Handedness and hemispheric asymmetry in the control of movements. Journal of Motor Behavior, 10,295-300.

Todor, J.I., & Kyprie, P.M. (1980). Hand differences in the rate and variability of rapid tapping. Journal of Motor Behavior, 12,57-60.

Todor, J.I., & Kyprie, P.M. & Price, H.L. (1982). Lateral asymmetries in arm, wrist and finger movements. Cortex, 18, 5 15-523.

Page 254: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Todor, J.I., & Smiley, A.L. (1985). Performance differences between the hands: Implications for studying disruption to limb proxis. In E.A. Roy (Ed.), Neuropsychological studies of apraxia and related disorders. Elsevier, North Holland.

Todor, J.I., & Smiley-Oyen, A.L. (1987). Force modulation as a source of hand differences in rapid finger tappping. Acta Psychologica, 65, 65-73.

Townsend, J.T. (1972). Some results concerning the identifiability of parallel and serial processes. British Journal of Mathematical and Statistical Psychology, 25,168- 199.

Trevarthen, C.B. (1968). Two mechanisms of vision in primates. Psychol. Forsch., 31, 299-337.

Trevarthen, C. (1974). Analysis of cerebral activities that generate and regulate consciousness in commissurotomy patients. In S.J. Dimond & J.G. Beaumont (Eds.), Hemisphere function in the human brain. New York: John Wiley & Son.

Trevarthen, C. (1984). How control of movement develops. In H.T.A. Whiting (Ed.), Human motor actions: Berstein reassessed. Amsterdam, North Holland.

Trevarthen, C., & Levy, J. (1973). The perception of movement and orientation in space by split brain patients. Cited in Levy, J. (1974) Psychobiological implications of bilateral asymmetry. In S.J. Dimond & J.G. Beaumont (Eds.), Hemisphere in the human brain. New York: John Wiley & Son.

Turvey, M.T., & Carello, C. (1986). The ecological approach to perceiving-acting: A pictorial essay. Acta Psychologica, 63, 133-155.

Van Wagenen, W., & Herren, R. (1940). Surgical division of commissural pathways in the corpus callosum. Archives of Neurology and Psychiatry, 44,740-759.

Vauclair, J., & Fagot, J. (1987). Visually guided reaching in adult baboons. Behavioral and Brain Sciences, 10,287.

Von Economo, C., & Horn, L. (1930). Uber windungsrelief, masse, und rindenarchitektonick der supratemporalflache. 2. Ges. Neurol. Ps ychiat., 130, 678-757.

Wada, J.A., Clark, R., & Harnrn, A. (1975). Cerebral hemispheric asymmetry in humans. Archives of Neurology, 32,239-246.

Wadrnan, W.J., Denier van der Gon, J.J., Geuze, R.H., & Mol, C.R. (1979). Control of fast goal directed arm movements. Journal of Human Movement Studies, 5,3- 17.

Wallace, R.J. (197 1). S-R compatibility and the idea of a response code. Journal of Experimental Psychology, 88,354-360.

Warrington, E.K., & Rabin, P. (1970). Perceptual matching in patients with cerebral lesions. Neuropsychologia, 8, 474-487.

Page 255: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Weinstein, S. (1978). Functional cerebral hemispheric asymmetry. In M. Kinsbourne (Ed.), Asymmetrical function of the brain. Cambridge, MA: Cambridge University Press.

Weiskrantz, L., Warrington, E.K., Sanders, M.D., & Marshall, J. (1974). Visual capacity in the hemianopic field following a restricted occipital ablation. Brain, 97,709- 728.

Welford, A.T. (1971). Fundamentals of skill. London: Methuen.

Wernicke, C. (1874). Der aphasische syrnptomencomplex. Breslau: Max Cohn and Weigert.

White, M.J. (1969). Laterality differences in perception: A review. Psychological Bulletin, 72, 387-405.

Wilson, W.R., & Miller, H. (1964). A note on the inconclusiveness of accepting the null hypothesis. Psychological Review, 71, 238-242.

Witelson, S.F., & Pallie, W. (1973). Left hemisphere specialization for language in the newborn: Anatomical evidence of asymmetry. Brain, 96,641-646.

Witelson, S.F. (1974). Hemispheric specialization for linguistic and non linguistic tactual perception using dichotomous stimulation techniques. Cortex, 10, 1- 17.

Wolff, P.H., Hurwitz, I., & Moss, H. (1977). Serial organization of motor skills in left and right handed adults. Neuropsychologia, 15,539-546.

Woodworth, R.S. (1899). The accuracy of voluntary movements. Psychological Review, 3, (2, Whole No. 13).

Wyke, M. (1966). Postural arm drift associated with brain lesions in man. Archives of Neurology, 15, 329-334.

Wyke, M. (1967). Effects of brain lesions on the rapidity of arm movement. Neurology, 17, 11 13-1 120.

Wyke, M. (1968). The effect of brain lesions in the performance of an arm-hand precision task. Neuropsychologia, 6, 125- 134.

Wyke, M. (1969). Influence of direction on the rapidity of bilateral arm movements. Neuropsychologia, 7, 189- 194.

Wyke, M.A. (1981). The nature of cerebral hemispheric specialisation in man: Quantitative vs. qualitative differences. The Behavioral and Brain Sciences, 4,78-79.

Yarnadori, A.Z., Osumi, Y., Masuhara, S., & Okubo, M. (1977). Preservation of singing in Broca's aphasia. Journal of Neurology, Neurosurgery and Psychiatry, 40,221- 224.

Young, A.W., & Ellis, A.W. (1979). Perception of numerical stimuli felt by fingers of the left and right hands. Quarterly Journal of Experimental Psychology, 3 1,263-272.

Page 256: RICHARD G. CARSON B.Sc, (Wons) Psychology, University of Bristolsummit.sfu.ca/system/files/iritems1/5400/b15027430.pdf · 2021. 4. 1. · THE ASYMMETRICAL REGULATION OF POINTING MOVEMENTS

Young, R. (1987, October). The visual control of aiming movements made to stationary and moving targets. Paper presented at the Canadian Psychomotor Learning and Sport Psychology Conference, Banff, Alberta.

Zaidel, D., & Sperry, R.W. (1977). Some long term effect of cerebral commissurotomy in man. Neuropsychologia, 15, 193-204.

Zaidel, E. (1973). Linguistic competence and related functions in the right cerebral hemisphere of man following commissurotomy and hemispherectomy. Doctoral dissertation, California Institute of Technology.

Zaidel, E. (1978). Auditory language comprehension in the right hemisphere following cerebral commissurotomy and hemispherectomy : A comparison with child language and aphasia. In A. Caramazza & E. Zurif (Eds.), Language acquisition and language breakdown. Baltimore: John Hopkins University Press.

Zangwill, D.L. (1 960). Cerebral dominance and its relation to psychological function. Edinburgh: Oliver and Boyd.

Zelaznik, H.N., Hawkins, B., & Kisselburgh, L. (1983). Rapid visual feedback processing in single aiming movements.Journal of Motor Behavior, 15,217-236.

Zelaznik, H.N., Hawkins, B., & Kisselburgh, L. (1987). The effects of movement distance and movement time on visual feedback processing in aimed hand movements. Acta Psychologica, 65, 18 1- 19 1.