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Effects of manipulating relative and absolutemotion information during observationallearning of an aiming taskSaleh A. Al-Abood a , Keith Davids a , Simon J. Bennett a , Derek Ashford a &Manuel Martinez Marin ba Psychology Research Group, Department of Exercise and Sport Science , TheManchester Metropolitan University , Hassall Road, Alsager ST7 2HL, UKb Facultad de Ciencias del Deporte , University of Granada , Granada, SpainPublished online: 01 Dec 2010.

To cite this article: Saleh A. Al-Abood , Keith Davids , Simon J. Bennett , Derek Ashford & Manuel Martinez Marin(2001) Effects of manipulating relative and absolute motion information during observational learning of anaiming task, Journal of Sports Sciences, 19:7, 507-520, DOI: 10.1080/026404101750238962

To link to this article: http://dx.doi.org/10.1080/026404101750238962

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Eþ ects of manipulating relative and absolute motioninformation during observational learning

of an aiming task

SALEH A. AL-ABOOD,1* KEITH DAVIDS,1 SIMON J. BENNETT,1

DEREK ASHFORD 1 and MANUEL MARTINEZ MARIN2

1Psychology Research Group, Department of Exercise and Sport Science, The M anchester Metropolitan University,

Hassall Road, Alsager ST7 2HL, UK and 2Facultad de Ciencias del Deporte, University of Granada, Granada, Spain

Accepted 22 March 2001

In the visual perception perspective of observational learning, the manipulation of relative and absolute motion

information in visual demonstrations optimally directs learners’ search towards appropriate task solutions.

We assessed the eþ ect of emphasizing transformational information and removal of structural information

using point-light kinematic displays in approximating the model’ s relative motion patterns. Participants viewed

computer-simulated point-light demonstrations or normal video demonstrations before and intermittently

throughout 100 acquisition trials with knowledge of results on an underarm modi® ed-dart aiming task. On the

next day, all participants performed 20 retention trials without demonstrations. The kinematics of spatial and

temporal coordination and control variables were examined relative to the model’ s action, as well as performance

scores. The results indicated that approximation of the model’ s spatial and temporal coordination and control

patterns was achieved after observation of either type of demonstrations. No diþ erences were found in move-

ment outcomes. In a second experiment, the eþ ects of manipulating absolute motion information by slow-

motion demonstrations were examined relative to real-time demonstrations. Real-time demonstrations led to

a closer approximation to the model’ s spatial and temporal coordination patterns and better outcome scores,

contradicting predictions that slow-motion displays convey intact relative motion information. We speculate that

the eþ ect of visual demonstration speed on action perception and reproduction is a function of task constraints ±

that is, novelty or familiarity of relative motion of demonstrated activities.

Keywords : control, coordination, informational constraints, skill acquisition, visual demonstrations.

Introduction

An important task for sport scientists interested in

motor skill acquisition is to evaluate the eþ ectiveness

of diþ erent types of visual demonstrations during sports

coaching, training and practice. Scully and Newell

(1985) conceptually integrated evidence from research

on the perception of biological motion with Newell’ s

(1985) framework of learning stages (i.e. coordination,

control, skill) and proposed a visual perception per-

spective on observational learning as an alternative to

traditional theories. Central to this visual perspective

is the tenet that visual demonstrations should be used

* Author to whom all correspondence should be addressed. e-mail:

s.a.al-abood@mmu.ac.uk

primarily to transmit relative motion information

essential to the task being learned or performed. From

this standpoint, it has been argued that one important

role of visual demonstrations during skill acquisition

is the manipulation of this source of movement

information, so that the search by learners to assemble

eþ ective coordination patterns is optimally directed

towards appropriate task solutions (Scully and Newell,

1985; Williams et al., 1999).

On the basis of this new theoretical rationale for

observational learning e þ ects, Scully (1988) suggested

some practical implications for the use of visual

demonstrations in teaching and coaching motor skills.

We address some of the important questions related

to the arguments proposed by Scully, in an attempt to

examine the empirical support for these suggestions.

Journal of Sports Sciences, 2001, 19, 507 ± 520

Journal of Sports Sciences ISSN 0264-041 4 print/ISSN 1466-447 X online Ó 2001 Taylor & Francis Ltdhttp://www.tandf.co.uk/journals

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Speci® cally, we assessed whether the use of point-

light displays can facilitate further the acquisition of

movement coordination compared to normal video-

taped demonstrations. We also examined whether

slow-motion videotaped demonstrations interfere with

the pick-up of relative motion information and the

perception of temporal parameters of a modelled action

compared to real-time demonstrations, as hypothesized

by Scully (1988).

In the ® rst study reported in this paper, we examined

the hypothesis that the use of point-light or kinematic

displays in visual demonstrations can aid the pick-up of

relative motion information, facilitating the acquisition

of movement coordination underlying the task being

learned (Scully, 1988). This prediction is based on the

argument that kinematic displays convey only trans-

formational information essential to perceiving biological

motion and minimizing structural information.

Previous research on visual perception of human

motion has consistently demonstrated that transform-

ational information (i.e. information about the move-

ment of an individual) conveyed by point-light displays

is su ý cient for observers to discriminate between

diþ erent classes of physical activities, such as walking,

running, cycling, dancing (Johansson, 1973, 1975),

throwing (Williams, 1985) and throwing and bowling

(Scully, 1987). Moreover, the removal of structural

information ± information about the shape, colour,

size and other characteristics of a performer ± did not

hinder observers’ identi ® cation and recognition of

activities. Research has also shown that kinematic dis-

plays aþ ord the perception of dynam ic parameters

of observed activities, such as force (Runeson and

Frykholm, 1981), speed (Scully, 1987; Williams, 1989)

and even technical execution and aesthetic quality in

gymnastics (Scully, 1986). Accordingly, the results of

these perception studies are su ý ciently compelling to

consider whether kinematic point-light displays can aid

perception in the modelling process (Williams et al.,

1999).

To date, few studies have examined whether point-

light displays can be at least as e þ ective as normal video-

taped demonstrations in supporting the performance

and learning of motor skills. The lim ited ® ndings

suggest that further research is required before practical

implications can be advised. For example, Williams

(1985) examined the e þ ect of presenting point-light

displays and normal videotaped demonstrations on

observers’ performance of a throwing action consisting

of a sequence of 2 ± 8 sub-movements. The results

indicated no diþ erences in the production of limb dis-

placement and timing (phasing) between observers of

point-light displays and normal videotapes. However,

as there was no retention or transfer test, Williams did

not compare the e þ ects on learning of using diþ erent

types of display. There were also several inherent

methodological limitations, the most important of

which was that the point-light displays demonstrated

only the throwing arm without the torso, which may

have mediated observers’ perception of movement.

When point-light displays are used in perception

research, researchers typically use points representing

the key joints of the whole body rather than just those

directly involved in the movement. Furthermore,

Williams (1985) did not consider how kinematic

displays in¯ uence movement outcome scores. Con-

sequently, in the ® rst study reported here, we tried to

establish the eþ ect of point-light displays, compared

to normal videotaped demonstrations, on the learning

of an aiming task by including more practice trials and

a retention test in the design. Moreover, we wished

to determine the eþ ect of these displays on movement

outcomes as well as movement kinematics, which

would allow us to investigate the acquisition of move-

ment coordination and control, as operationalized by

Scully and Newell (1985).

In a second study, we examined whether the obser-

vation of slow-motion videotaped demonstrations has

facilitative or detrimental e þ ects on the acquisition

of movement coordination and control, as well as task

outcomes, compared to videotaped demonstrations pre-

sented in real-time. This is an issue of some signi® cance

to sport scientists, since it has practical as well as

theoretical implications for those involved in sports

coaching and training. Previous research on this

issue has been equivocal. For example, Nelson (1958)

found no signi® cant diþ erences in outcome scores when

observing a golf swing between a slow-motion group

and a real-time videotape group. However, the slow-

motion group did show a greater gain in scores later in

practice, while the real-time modelling group showed a

greater gain earlier. McGuire (1961) studied the eþ ect

of demonstrating some steps of performance on a

pursuit-rotor tracking task in slow motion while keeping

other steps at real-time speed. He found enhanced

performance for the items presented in slow motion,

whereas performance on other items was impaired.

Williams (1985, 1989) assessed the eþ ects of slowing

down or speeding up the presentation of a throwing

action in normal videotaped demonstrations or

point-light displays and found that slow-motion

demonstrations embedded correct reproduction of

timing parameters of an action but had little eþ ect on

limb displacement. More recently, and using a more

complex action ± a ballet dance sequence ± Scully and

Carnegie (1998) found that the observation of slow-

motion demonstrations, compared to normal-speed

demonstrations, slightly facilitated the pick-up and

replication of the model’ s coordination function (e.g.

relative timing). However, slow motion was found to

508 Al-Abood et al.

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have impaired the pick-up and replication of movement

control parameters such as movement time and force.

Visual perception research has also revealed mixed

® ndings on the relative e ý cacy of slow-motion and real-

time video demonstrations. For example, Barclay et al.

(1978) found that slow motion hindered action recog-

nition, while Scully (1987) observed little in¯ uence on

action identi® cation but an e þ ect for speed discrimi-

nation. Although Cutting and Pro ý tt (1982) indicated

that real-time demonstrations are essential to the per-

ception of a frame of reference for each activity, Scully

(1988) theorized that slow-motion displays provide the

same relative motion demonstrated by normal video-

tapes but exaggerate the temporal parameters of a

modelled action. In other words, slow-motion displays

oþ er intact relative motion information of an action

but convey distorted `unreal-time’ features of the action,

thus destroying the perception of absolute motion.

Relating the visual perception perspective on obser-

vational learning to Newell’ s (1985) model of motor

learning results in two major predictions on the use

of slow-motion demonstrations. First, it is expected

that slow-motion will be as e þ ective as real-time

demonstrations in supporting the reproduction of an

observed coordination pattern. Secondly, slow motion

is predicted to impair the approximation of control

parameters of the demonstrated action.

In short, although few perception and action studies

have examined the eþ ectiveness of viewing slow-motion

as opposed to real-time demonstrations, the evidence is

still inconclusive and further research is required before

practical implications can be proposed. Accordingly, the

aim of the second experiment was to address this issue

from a visual perception perspective.

Experiment 1

The main aim of Experiment 1 was to establish whether

demonstrating an action with a point-light kinematic

display, compared to a normal videotaped display,

would aid further the pick-up of relative motion

information, facilitating the acquisition of a movement

coordination pattern. We hypothesized that, if point-

light displays do support the pick-up of relative motion

information, observers of point-light displays should

show a greater, or at least an equal, approximation to

the temporal and spatial relative motion patterns

demonstrated by a model than observers of normal

videotapes of the same action. Furthermore, in relation

to Newell’ s (1985) model of motor learning, we

also wished to determine whether point-light displays

have the potential to support the pick-up of move-

ment control variables such as movement time and

velocity.

Methods

Participants. Ten male participants (mean age = 24.2

years) volunteered for the experiment. They were all

right-handed and had normal or corrected-to-normal

vision. All participants were naive to the experimental

task, provided informed consent before participation

and were told that they were free to withdraw at any time.

Apparatus and task. The task involved an underarm

throw of a modi® ed dart originally used by Al-Abood

et al. (in press). The aim of the task was to score as many

points as possible by aiming the modi® ed dart with the

dominant arm towards a target dartboard. The target

was a standard dartboard (Unicorn) modi® ed for the

outcome scoring system of the experiment. It contained

10 concentric circles. The bullseye had a diameter of

2.25 cm, with each other circle increasing by 2.25 cm

in radius. To provide outcome scores as a dependent

variable, the bullseye was awarded 10 points, with

each concentric circle radiating out from the bullseye

decreasing by one point so that the outermost circle was

worth only one point. The target was placed on the ¯ oor

3 m away from a throwing line. A regular (Unicorn) dart

was also modi® ed by attaching an additional shaft to

the free end of the ¯ ight. This allowed the participants

to hold the dart from its end, permitting an underhand

aiming movement. The modi® ed dart had a mass of 40 g

and was 20 cm long (see Fig. 1).

The task was unfamiliar to all participants and

involved multiple biomechanical degrees of freedom,

permitting the examination of modelling eþ ects on

movement coordination and control (McDonald et al.,

1989).

Data collection and demonstration preparation. An

ELITE on-line motion analysis system (see Pedotti and

Ferrigno, 1995) was used to collect and analyse move-

ment kinematics. Three markers were positioned on

three joints of the dominant arm (i.e. the right upper

limb) of the model and all participants: the acromion

process of the shoulder and the lateral condyles of

the elbow and wrist. A fourth marker was attached to

the modi® ed dart at the additional shaft to determine

the release time of the dart. The two-dimensional

coordinate data were recorded on-line at a sampling fre-

quency of 100 Hz. After testing, the three-dimensional

coordinates were reconstructed from the transformed

two-dimensional coordinate data of the re¯ ective

markers recorded from the two cameras. Then, the

raw displacement data were ® ltered with a recursive

second-order Butterworth ® lter with a cut-oþ frequency

of 5 Hz, which was applied twice to negate the phase

shift (Wood, 1982). The ® ltered displacement data were

then diþ erentiated oþ -line to derive velocity data.

Visual demonstrations and skill acquisition 509

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Fig. 1. The underhand modi® ed-dart aiming task.

Finally, the resultant displacement and velocity data

were calculated.

A video camera (Panasonic, F-15) and recorder

(Samsung, SV 821K) were used to videotape the model

for later demonstrations. Before being videotaped, the

model practised 3000 trials on the experimental task

over 30 days at a rate of 100 trials per day. The model

was videotaped during the ® nal 20 trials on the last

day of practice. Then, a videotaped colour recording

was edited by selecting six representative trials to be

presented as visual demonstrations to participants. The

mean outcome score for these selected trials was 8.8 out

of a maximum possible score of 10 points. The viewing

time of the videotape recording was approximately 3

min. The view of the demonstrations in this videotape

recording contained the model’ s whole body movement,

the target and the trajectory of the dart. The videotape

recording also provided auditory knowledge of results

after every trial demonstrated by the model. To present

the videotape demonstrations to the participants, the

videotape recorder was connected to a colour television

(Hantarex, screen dimensions = 65 ´ 50 cm).

While the model was being videotaped, a record of

his movement kinematics was also taken via the ELITE

system following the aforementioned procedures. The

model’ s kinematic data were collected for later com-

parative analyses. Speci® cally, for all trials demonstrated

by the model, angular displacement and velocity of the

aiming arm were calculated from the instant of move-

ment initiation to the release of the dart.

A computer-simulated point-light demonstration was

created based on the digitized kinematic data of the six

trials selected for presentation in the normal videotaped

recording for the model. Therefore, the point-light

display provided the same transformational movement

information demonstrated by the normal videotaped

presentation. However, no structural information was

available in the point-light display. In the point-light

demonstration, 21 points represented the key joints

of the model’ s body and two points represented the

dart. Furthermore, one segment-light and one point-

light represented the target and its centre, respectively.

A computer-based, rather than videotape, display was

used in the study to eliminate the detrimental e þ ect of

`blooming’ that may occur as a result of using bright

light sources against a dark background (Kozlowski and

Cutting, 1977).

Procedure. The participants were assigned at random

to one of two experimental treatment groups (n = 5):

normal-videotape group and the point-light group.

All participants followed the same experimental pro-

cedures but diþ ered with respect to whether they

observed normal videotaped demonstrations or point-

light demonstrations. All participants observed their

respective demonstrations before practice and inter-

mittently every 10 consecutive practice trials through-

out the acquisition session. Before and throughout

the retention trials, all participants performed with-

out observing any demonstrations. All participants

were instructed to use the information available in the

demonstrations to help them to perform the task and

to improve their performance. They also received pre-

liminary instructions from the experimenter on how to

hold the dart.

Each participant was tested individually in the

presence of the experimenter only. The study consisted

of two sessions, acquisition and retention, held on two

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consecutive days; these sessions consisted of 100 and

20 trials, respectively. The participants were allowed

2 min rest after every 20 acquisition trials. The time

between each set of 10 consecutive acquisition trials

was the same for participants in both groups. Each trial

was initiated by a `ready’ command given by the

experimenter approximately 2 s before the `go’ com-

mand to start the movement. All participants received

knowledge of results based on their performance on

each trial. Knowledge of results was provided for two

reasons: ® rst, to determine the potency of modelling

in motor skill acquisition when such knowledge is avail-

able; secondly, to generalize the ® ndings of the present

experiment to learning and performance settings in

which such knowledge is provided.

Dependent measures. Data on movement outcomes

and kinematics were collected for all acquisition and

retention trials following the data collection procedures

described above. However, for movement kinematics

only, the ® rst six and last six acquisition trials as

well as the ® rst six retention trials were analysed.

One movement outcome measure and several move-

ment kinematic measures were selected as appropriate

variables to examine the predictions advanced in this

study about the eþ ects of visual demonstrations on

movement outcomes, coordination and control.

Movement outcomes. To determine the e þ ects of

the type of demonstrations on movement outcomes,

means and standard deviations (s) of performance

scores were calculated to establish the aiming accuracy

of each participant for each block of 10 trials. This

procedure resulted in 10 acquisition and two reten-

tion blocks. The resultant data were submitted to

separate (2 groups ´ 12 trial blocks) two-factor analyses

of variance (ANOVA) with repeated measures on the

trial blocks.

Movement coordination (relative motion). To examine

the eþ ects of the type of demonstrations on movement

coordination, we used the relative motion of upper-

and lower-arm segments of the aiming arm. Speci® cally,

we computed angular velocities and displacements of

arm segments to the vertical axis from the start signal

to the instant of dart release. The positions of these two

segm ents to the vertical represent the most coherent

shape in terms of the topological properties of a throw-

ing arm (Scully, 1987).

To determine precisely the approximation of par-

ticipants’ relative motion patterns to those of the

model, a cross-correlation of recognition coeý cient (R )

(Sparrow et al., 1987) was calculated between the

median relative motion values of the model and that of

every trial performed by a participant and included in

the analysis. The cross-correlation of recognition co-

eý cient is a measure of the extent to which the angles

between adjacent data points from one angle± angle

or velocity± velocity plot are sim ilar to angles from

another plot. It is a measure of similarity between two

coordination patterns. The value of cross-correlation

(R) ranges from -1.0 to +1.0 according to the similarity.

As R approaches zero, the velocity± velocity or angle ±

angle relative motions of two plots become increasingly

dissimilar in shape. In the present study, therefore,

the higher the positive R-value, the greater the approxi-

mation to the model’ s relative motion.

To calculate cross-correlations, we followed three

steps. First, one movement pattern was selected as

representative of the six trials demonstrated by the

model. To determine the model’ s median pattern, we

plotted all relative motions of the model’ s six trials

in a single angle ± angle diagram and velocity± velocity

diagram. From these motions, we selected the median

relative motions of the model (see Fig. 2). Secondly,

after selecting the model’ s median pattern, all par-

ticipants’ trials were time-normalized to the same

number of data points as the model’ s pattern using a

cubic spline interpolation technique. Finally, a cross-

correlation with a zero-time lag was calculated between

each participant’ s trial and the model’ s median trials.

These procedures were ® rst followed to calculate cross-

correlations for spatial coordination (i.e. angle± angle

relations) and were then repeated to compute temporal

coordination (i.e. velocity± velocity relations).

After calculating cross-correlations, means and

standard deviations of cross-correlations were computed

for each participant for the ® rst six acquisition trials,

the last six acquisition trials and the ® rst six retention

trials. Standard deviations were computed as an index

of within-participant variability in coordination

patterns around the model’ s median pattern. The

cross-correlations were averaged by using a Fischer Z-

transformation procedure. The calculated means and

standard deviations of cross-correlations were sub-

mitted to separate (2 groups ´ 3 trial blocks) two-factor

multivariate analyses of variance (MANOVA) with

repeated measures on the trial block factor.

Movement control. Although there were various

kinematic variables available to examine the e þ ects of

demonstration type on movement control, we decided

to focus on those variables re¯ ecting the control of

elbow angle. Changes in this angle represent the scaling

or parameterization of the coordination function of

upper- and lower-arm segments (Scully, 1987). The

selected variables were: elbow angle at release, elbow

velocity at release and movement time (i.e. the time

taken from the start signal to release of the dart). For

each variable, means and standard deviations for each

Visual demonstrations and skill acquisition 511

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Fig. 2. Angle± angle (a) and velocity± velocity (b) relative motion patterns for the six trials selected for the model. The abbrevi-

ations Int, Rev and Rel indicate the instants of movement initiation, arm reversal and dart release respectively.

block of six trials were calculated for each participant.

Separate multivariate analyses of variance (2 groups ´3 trial blocks: Acquisition 1, Acquisition 2 and Reten-

tion), with repeated measures on the last factor, were

computed on the control variables.

Signi ® cance for all statistical analyses conducted in

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this study was set at a = 0.05. For repeated-measure

analyses, the Huynh-Feldt correction factor was used

to adjust the degrees of freedom of the univariate F

because of the potential violation of the sphericity

assumption owing to the many levels of the repeated

measures (see Schutz and Gessaroli, 1987). Further-

more, signi® cant multivariate analyses of variance were

followed by separate univariate analyses of variance and

discriminant analysis (i.e. standardized coeý cients) to

determine which of the dependent variables contributed

most to signi® cant diþ erences within each factor (Bray

and Maxwell, 1985; Schutz and Gessaroli, 1987). The

values reported for the multivariate analyses of variance

are Wilks’ lambda ratios. Signi® cant analyses of variance

were followed by Tukey HSD tests when required.

Results

Movement outcome. The ANOVA on mean outcome

scores showed no signi® cant e þ ect for groups (F1,8 =1.28, P = 0.29) or groups ´ trial blocks interactions

(F11,88 = 1.21, P = 0.29). However, there was a signi® -

cant main eþ ect for trial blocks (F11,88 = 2.37, P = 0.01).

Univariate analysis, including a Huynh-Feldt procedure

to adjust the degrees of freedom because of a violation

of the sphericity assumption, maintained the trial block

eþ ect (F11,88 = 2.37, P = 0.013). Follow-up Tukey HSD

tests on the block factor revealed an improvement in

movement outcome with practice. The performance of

both groups on the second retention block was signi® -

cantly better than that on the ® rst acquisition block

(P = 0.00). No other signi® cant diþ erences were found,

although the diþ erences between the ® rst acquisition

block and the seventh and eighth acquisition blocks

approached conventionally accepted levels of statistical

signi® cance (P = 0.06; see Table 1).

For standard deviations of outcome scores, there

was no main eþ ect for groups (F1,8 = 0.291, P = 0.60) or

trial blocks (F11,88 = 1.14, P = 0.34), or a groups ´ trial

blocks interaction (F11,88 = 1.04, P = 0.42).

Movement coordination (relative motion). The multi-

variate analyses of variance computed on the means

of velocity± velocity cross-correlations and angle± angle

cross-correlations showed no main e þ ect for groups

(Wilks’ l2,7 = 0.865, P = 0.60) or trial blocks (Wilks’

l4,5 = 0.296, P = 0.13), or a groups ´ trial blocks inter-

action (Wilks’ l4,5 = 0.655, P = 0.65) (see Table 2).

For standard deviations of cross-correlations, as an

index of intra-individual variability of movement

coordination, no signi® cant diþ erence was observed

between groups (Wilks’ l2,7 = 0.861, P = 0.59) or trial

blocks (Wilks’ l4,5 = 0.538, P = 0.46), and there was no

groups ´ trial blocks interaction (Wilks’ l4,5 = 0.839,

P = 0.90) (see Table 2).

Table 1. Movement outcomes as a function of groups and

trial blocks (mean ± s)

Trial

block

Normal-videotape

group

Point-light

group

Acquisition

1

2

3

4

5

6

7

8

9

10

3.20 ± 2.96

3.52 ± 3.13

4.84 ± 3.12

4.84 ± 2.97

4.50 ± 2.92

5.32 ± 3.07

5.24 ± 2.92

4.86 ± 2.92

5.24 ± 2.41

4.76 ± 2.86

3.20 ± 3.21

4.06 ± 2.69

3.84 ± 2.66

3.62 ± 2.45

3.92 ± 2.98

3.46 ± 2.64

4.12 ± 3.33

4.52 ± 2.80

3.56 ± 2.58

4.22 ± 2.59

Retention

1

2

4.66 ± 2.80

5.26 ± 3.00

4.16 ± 3.15

5.18 ± 3.09

Table 2. Cross-correlations of recognition coeý cient (R) as a function of groups

and trial blocks (mean ± s)

Trial block

Acquisition 1 Acquisition 2 Retention

Angle ± angle (R)

Normal-videotape group

Point-light group

Slow-motion group

0.46 ± 0.10

0.42 ± 0.08

0.39 ± 0.09

0.56 ± 0.06

0.52 ± 0.06

0.43 ± 0.05

0.52 ± 0.09

0.51 ± 0.06

0.42 ± 0.05

Velocity± velocity (R )

Normal-videotape group

Point-light group

Slow-motion group

0.43 ± 0.05

0.42 ± 0.04

0.37 ± 0.04

0.52 ± 0.04

0.48 ± 0.04

0.41 ± 0.03

0.49 ± 0.05

0.45 ± 0.04

0.42 ± 0.03

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Table 3. Movement control variables as a function of groups and trial blocks (mean ± s)

Trial block

Acquisition 1 Acquisition 2 Retention

Release angle ( 8 )

Normal-videotape group

Point-light group

Slow-motion group

142 ± 1.80

138 ± 4.07

142 ± 8.44

138 ± 5.78

142 ± 4.03

143 ± 4.40

138 ± 1.57

137 ± 3.70

142 ± 4.63

Release velocity (degrees per second)

Normal-videotape group

Point-light group

Slow-motion group

61.8 ± 20.6

104 ± 40.6

74.2 ± 42.9

87.6 ± 31.8

84.5 ± 42.4

108 ± 31.1

94.6 ± 41.1

75.2 ± 31.3

72.9 ± 35.5

Movem ent tim e (m s)

Normal-videotape group

Point-light group

Slow-motion group

1469 ± 156

1550 ± 169

1597 ± 367

1727 ± 86

1922 ± 135

1847 ± 168

1636 ± 74

1718 ± 115

1757 ± 123

Movement control. The multivariate analyses of vari-

ance on the means of elbow release angle, elbow release

velocity and movement time showed no signi® cant

diþ erences between groups (Wilks’ l3,6 = 0.921, P =0.91) or trial blocks (Wilks’ l6,3 = 0.152, P = 0.21), and

there was no groups ´ trial blocks interaction (Wilks’

l6,3 = 0.266, P = 0.43). Similarly, there were no sig-

ni® cant e þ ects for groups (Wilks’ l3,6 = 0.700, P = 0.51)

or trial blocks (Wilks’ l6,3 = 0.281, P = 0.45), or a

groups ´ trial blocks interaction (Wilks’ l6,3 = 0.368,

P = 0.55), when a MANOVA was computed on the

standard deviations of the same dependent variables

(see Table 3).

Discussion

The aim of Experiment 1 was to determine whether

point-light kinematic displays, compared to normal

videotaped displays, support further the pick-up of rela-

tive motion information, thus facilitating the acquisition

of a movement coordination pattern. We hypothesized

that if point-light displays do facilitate the pick-up

of relative motion information, compared to normal

videotapes, participants observing point-light displays

should show a closer, or at least an equal, approximation

to the temporal and spatial relative motion patterns

demonstrated by the model. This prediction was

supported in part, since no diþ erences in approximating

the model’ s relative motion patterns were observed

between participants in the two groups. This suggests

that the transformational information available in point-

light kinematic displays was su ý cient to convey relative

motion information to observers learning an under-

arm throw. This is consistent with ® ndings of visual

perception research for the potency of such displays

in transmitting accurate information about physical

activity identi® cation and recognition (Johansson, 1973,

1975; Williams, 1985; Scully, 1987).

The analysis of movement control variables also

showed no group diþ erences caused by type of visual

demonstrations. Again, the results suggest that point-

light displays were as eþ ective as normal videotape

demonstrations in conveying information about move-

ment control. This is also consistent with ® ndings in

visual perception research (Scully, 1987; Williams,

1989), indicating that the removal of structural infor-

mation has no detrimental eþ ect on the perception of

control-relevant information. The results are also con-

sistent with the work of Williams (1985), who found no

diþ erences in production of movement timing between

observers of point-light displays and normal demonstra-

tions. Moreover, the results of the present study extend

Williams’ ® ndings to learning contexts.

Finally, for achieving the goal of the movement (i.e.

outcome scores), the observation of point-light displays

was also found to be as eþ ective as the observation of

normal videotaped demonstrations.

Experiment 2

The main aim of Experiment 2 was to assess the eþ ect

of slow-motion demonstrations, compared to real-time

demonstrations, on the acquisition of movement co-

ordination and control of an aiming task. Visual per-

ception research has revealed mixed results on how

slow motion demonstrations in¯ uence perception of

movement characteristics. Furthermore, the eþ ect of

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slow-motion demonstrations on movement production

has typically received little attention in the modelling

literature, although this method of instruction is com-

monly used by instructors of motor skills. This lack

of consideration may have been due in part to a lack of

understanding of the nature of movement information

conveyed by visual demonstrations in traditional per-

spectives on observational learning. However, Scully

(1988) suggested that slow-motion displays provide

the same relative motion demonstrated by normal

videotapes, but distort the temporal parameters of a

modelled action. Slow-motion displays oþ er intact rela-

tive motion information of an action but convey `unreal’

time features of that action, perturbing the perception

of absolute motion. Accordingly, a key prediction on

the use of slow-motion demonstrations from a visual

perception perspective is that slow-motion will be as

eþ ective as normal real-time demonstrations for the

reproduction of an observed coordination pattern,

although it may impair the approximation of control

aspects of the demonstrated action.

Methods

Participants. Five additional male participants (mean

age = 23.2 years), none of whom participated in Experi-

ment 1, volunteered for this experiment. All participants

were right-handed and had normal or corrected-to-

normal vision. They were naive to the experimental task,

provided informed consent before participation and

they were told that they were free to withdraw at any

time.

Apparatus and task. The task and apparatus were the

same as those used in Experiment 1.

Data collection and demonstration preparation. The

procedures used to collect kinematic data in Experi-

ment 1 were followed in Experiment 2. Furthermore,

the videotaped demonstrations by the skilled model

prepared in Experiment 1 were presented in slow

motion for participants in the slow-motion group in

Experiment 2. The viewing time of the videotape

recording presented in slow motion was approximately

4.5 min.

Procedure. The ® ve additional participants who

volunteered for this experiment were assigned to the

slow-motion group. To examine the predictions

advanced for this experiment, this group was compared

to the normal-videotape group who viewed normal

videotape demonstrations presented in real time in

Experiment 1. All participants in the slow-motion

group followed the same experimental procedures as

the normal-videotape group in Experiment 1 for the

number of acquisition and retention trials, knowledge

of results and inter-block rest intervals. However, the

groups diþ ered with respect to the nature of the visual

demonstrations they observed; the participants in the

normal-videotape group viewed normal real-time video-

taped demonstrations (a normal ® lm rate of 25 Hz),

whereas those in the slow-motion group observed slow-

motion demonstrations (15 Hz) of the same movement.

Participants in both groups viewed their respective

demonstrations before practice and intermittently every

10 consecutive practice trials throughout the acquisition

session. All participants were instructed to use the in-

formation available in the demonstrations to help them

to learn the task and to improve their performance.

Data analysis. In this experiment, the dependent

variables representing movement coordination, control

and outcome scores, as well as the statistical analyses,

were similar to those used in Experiment 1.

Results

Movement outcomes. The ANOVA computed on mean

outcome scores showed a signi® cant e þ ect for groups

(F1,8 = 9.32, P = 0.02) and trial blocks (F11,88 = 2.31,

P = 0.01); however, there was no signi® cant e þ ect for

the interaction between groups and trial blocks

(F11,88 = 1.42, P = 0.18). Inspection of the means of

both groups indicated that the normal-videotape group

(4.69) performed signi® cantly better than the slow-

motion group (3.10) (see Fig. 3). A univariate analysis,

including a Huynh-Feldt procedure to adjust the

degrees of freedom because of a violation of the

sphericity assumption, maintained the trial block

eþ ect (F11,88 = 2.37, P = 0.015). Follow-up Tukey HSD

tests on the block factor revealed improvement in

movement outcome with practice. The performance

of both groups on the eighth acquisition block

(mean = 4.44) and second retention block (mean =4.35) was signi® cantly better than that for the ® rst

acquisition block (mean = 2.83) (P = 0.01 and P = 0.02,

respectively).

For standard deviations of outcome scores, there

was no signi® cant e þ ect for groups (F1,8 = 0.507, P =0.50) or trial blocks (F11,88 = 1.22, P = 0.29), and there

was no groups ´ trial blocks interaction (F11,88 = 0.808,

P = 0.63).

Movement coordination (relative motion). The multi-

variate analyses of variance computed on the means

of velocity± velocity cross-correlations (temporal co-

ordination) and angle ± angle cross-correlations (spatial

coordination) showed signi® cant main e þ ects for groups

(Wilks’ l2,7 = 0.227, P = 0.01); however, no signi® cant

eþ ect was found for trial blocks (Wilks’ l4,5 = 0.393,

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Fig. 3. Mean movement outcomes as a function of the normal videotape group ( d ) and slow-motion group ( s ) across blocks of

10 practice trials.

Fig. 4. Angle± angle relative motion patterns for a representative participant from the normal videotape group (NVp) and slow-

motion group (SMp) on the last acquisition trial, compared to the median pattern of the model. The abbreviations Int, Rev and

Rel indicate the instants of movement initiation, arm reversal and dart release respectively.

P = 0.24) and there was no groups ´ trial blocks inter-

action (Wilks’ l4,5 = 0.319, P = 0.16).

Follow-up univariate analyses of variance and dis-

criminant analysis on the group e þ ect revealed signi® -

cant diþ erences between groups for both dependent

variables: spatial coordination (F1,8 = 22.1, P = 0.00)

and temporal coordination (F1,8 = 16.3, P = 0.00). The

discriminant functions (i.e. standardized coeý cients)

were -0.70 and -0.48 for spatial and temporal co-

ordination, respectively. Inspection of group means

for both dependent variables during acquisition and

retention revealed that participants in the normal-

videotape group had higher cross-correlations than

those in the slow-motion group, indicating closer

approximation to the skilled model’ s relative motion

(see Table 2 and Figs 4 and 5).

For standard deviations of cross-correlations, as an

estimate of intra-individual variability of movement

coordination, no signi® cant diþ erences were observed

between groups (Wilks’ l2,7 = 0.719, P = 0.32) or trial

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Fig. 5. Velocity± velocity relative motion patterns for a representative participant from the normal videotape group (NVp) and

slow-motion group (SMp) on the last acquisition trial, compared to the median pattern of the model. The abbreviations Int, Rev

and Rel indicate the instants of movement initiation, arm reversal and dart release respectively.

blocks (Wilks’ l4,5 = 0.571, P = 0.51), and there was no

groups ´ trial blocks interaction (Wilks’ l4,5 = 0.638,

P = 0.62) (see Table 2).

Movement control. The multivariate analyses of

variance on the means of elbow release angle, elbow

release velocity and movement time showed no signi® -

cant diþ erences between groups (Wilks’ l3,6 = 0.861,

P = 0.81) or trial blocks (Wilks’ l6,3 = 0.423, P = 0.68),

and there was no groups ´ trial blocks interaction

(Wilks’ l6,3 = 0.327, P = 0.53).

Similarly, there was no signi® cant e þ ect for groups

(Wilks’ l3,6 = 0.487, P = 0.20), or an interaction between

groups and trial blocks (Wilks’ l6,3 = 0.211, P = 0.32),

when a MANOVA was computed on the standard

deviations of the same dependent variables. However,

a signi® cant e þ ect was found for trial blocks (Wilks’

l6,3 = 0.021, P = 0.01).

Follow-up univariate analyses of variance and dis-

criminant analysis on the trial block e þ ect revealed

signi® cant diþ erences between trial blocks for move-

ment time only (F2,16 = 7.73, P = 0.00). The discrimi-

nant function (i.e. standardized coeý cient) was -0.61.

Follow-up Tukey HSD tests revealed a signi® cant

decrease in variability of movement time with practice.

The performance of both groups on the second acqui-

sition block and retention block was more consistent

than that in the ® rst acquisition block (see Table 3).

Discussion

The aim of Experiment 2 was to determine the e þ ect

of observing slow-motion demonstrations, compared

to real-time visual demonstrations, on motor skill

acquisition from a visual perception perspective

(Scully and Newell, 1985; Scully, 1988). According

to this perspective, slow-motion displays may convey

intact perception of relative motion information of a

demonstrated activity but may impede the recognition

of absolute motion parameters such as speed and

duration of an activity. Following this hypothesis,

and given that perception constrains action, we pre-

dicted that there would be no diþ erences in relative

motion patterns between the slow-motion and normal-

videotape groups. However, diþ erences due to speed

of demonstration were expected in movement control

variables such as velocity at release and movement time.

The results of this experiment showed that, through-

out the acquisition and retention sessions, participants

in the normal-videotape group approximated the

model’ s temporal and spatial relative motions more

closely than those in the slow-motion group. It was

apparent that observers of slow-motion demonstrations

were unable to perceive intact relative motion infor-

mation from these demonstrations, resulting in a less

accurate approximation of the model’ s relative motion

patterns. This ® nding does not concur with the pre-

dictions of the visual perception perspective. Rather,

the results are more consistent with the suggestion of

Cutting and Pro ý tt (1982) that demonstrating an

action in real-time is an indispensable procedure for

establishing accurate perception of a coordinate frame

of reference unique to each activity. This is also in line

with the work of Barclay et al. (1978), who reported

poor recognition of actions after the observation of

slow-motion presentations.

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One plausible explanation for the discrepancies

between the ® ndings of the present study and the

predictions of the visual perception perspective is

the novelty of relative motion patterns available in the

underarm-throwing task of this study. More generally,

it is possible that whether observers can perceive intact

information about relative motion from slow-motion

displays depends, to a large extent, on the observers’

familiarity with the experimental task. It is plausible that

altering the speed of demonstrations (i.e. a scaling up

or down of the optimal relative motion) will not impede

movement perception if observers have previously

viewed the task. Accordingly, it is possible that the par-

ticipants in the studies of Scully (1987) and Williams

(1985, 1989) were able to pick up and use appropriate

relative motion patterns because the overarm throwing

and bowling actions demonstrated in those experiments

were familiar to them. In contrast, if a slow-motion

manipulation of relative motion occurs with a novel

experimental task, then the perceptual pick-up of the

optimal relative motion underlying the successful per-

formance may be perturbed, thus hindering learning

as in this study. Further research is required to verify

this explanation by examining the e þ ects of learners’

perceptual experience on action perception and repro-

duction of novel and familiar tasks to be learned

through visual demonstrations presented in slow

motion.

The analysis of movement control variables (i.e.

elbow angle and velocity at release plus movement

time) indicated no diþ erences between participants

in the normal-videotape and slow-motion groups in the

reproduction of these variables during acquisition

and retention sessions. This is also inconsistent with

the predictions of the visual perception perspective. We

predicted that slow-motion presentations may hinder

the perception of movement control variables relevant to

the speed of movement and thus may lead to inaccurate

scaling of movement parameters. The present results

are also not in line with those of Williams (1985,

1989) and Scully and Carnegie (1998), who showed

incorrect reproduction of timing variables (e.g. absolute

timing, force) after the observation of slow-motion

demonstrations.

One possible explanation for these contradictory

® ndings about movement control is that participants in

the slow-motion group were able to discover appro-

priate timings of the aiming action through physical

practice. That is, because participants in the present

study had more physical practice (i.e. 100 trials) than

those in the studies of Williams (1989) and Scully

and Carnegie (1998) ± 6 and 10 trials, respectively ±

they were able to ® nd the appropriate control

parameters. Slow-motion demonstrations may have

hindered observers’ perception of movement timing

characteristics, but had little e þ ect on movement pro-

duction because learning was mediated by discovery

of key parameters through physical practice. However,

because perception was not assessed in the present

study, it is not possible to con® rm this.

Nevertheless, subsequent additional analyses of

movement production of these control variables on

the ® rst practice trial suggested that this explanation

may be plausible. We ran separate t-tests on the data

of the ® rst practice trial for each control variable in

an attempt to dissociate the e þ ect of observation of

demonstrations from that of physical practice. The

results showed no signi® cant diþ erences between the

slow-motion and normal-videotape groups in elbow

angle at release (t8 = 0.627, P = 0.55) and movement

time (t8 = -0.957, P = 0.37). However, a signi® cant

diþ erence between groups was found for elbow velocity

at release (t8 = -2.66, P = 0.03). The normal-videotape

group (mean = 49.5° per second) approximated the

model’ s velocity at release (mean = 48.1° per second)

much more closely than the slow-motion group

(mean = 131° per second).

Furthermore, although there were no group dif-

ferences in movement time, closer inspection of

individual data for each participant in both groups, and

of within-group standard deviations, revealed an inter-

esting ® nding. The movement times on the ® rst practice

trial of the participants in the normal-videotape group

ranged from 1200 to 1790 ms (s = 230), while those

of the participants in the slow-m otion group ranged

from 1040 to 2680 ms (s = 667). This implies that

the search by participants for the appropriate move-

ment time of the task was more constrained or directed

by the model’ s (mean = 1820 ms) movement time in

real-time demonstrations compared to slow-motion

presentations. Taken collectively and prompted by

initial ® ndings, further analyses of movement control

variables for the ® rst practice trial suggested that the

observation of slow-motion demonstrations could have

hindered the pick-up of absolute motion information.

However, through physical practice, the participants

in the slow-motion group were able to discover and

approximate the appropriate movement speed and time

essential for solving the task problem. Future research

should assess both perception and action to better

understand how manipulating absolute motion infor-

mation in visual demonstrations mediates action per-

ception and reproduction.

Finally, analysis of movement outcome scores indi-

cated that the normal-videotape group signi® cantly

outperformed the slow-m otion group during acqui-

sition and retention sessions. This suggests that the

closer approximation of the model’ s relative motion

by participants in the former group resulted in better

outcome scores.

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General discussion

In the experiments reported here, we examined the

eþ ect of manipulating relative and absolute motion

information available in visual demonstrations on the

acquisition of an aiming task from a visual perception

perspective of observational learning (Scully and

Newell, 1985; Scully, 1988).

As predicted, Experiment 1 showed that the

inclusion of structural information, found in normal

demonstrations, had little additional eþ ect on the

acquisition of movement coordination and control

or on maximizing outcome scores. The use of

point-light demonstrations, compared to normal

demonstrations, was of equal value in facilitating

the acquisition of movement coordination patterns

by emphasizing the relative motion information.

The implication is that learners can pick up relative

motion information from both normal videotaped

demonstrations of a skill and in point-light formats

to direct learners’ attention towards transformational

information. Because of evolutionary in¯ uences on

the human visual system, learners can pick up as

much transformational information from normal

demonstrations as from point-light displays to eþ ec-

tively use this source of information in subsequent

movement reproductions.

In Experiment 2, some evidence indicated that the

observation of slow-motion demonstrations, compared

to presentations at regular speed, was detrimental to

the approximation of the model’ s spatial and temporal

relative motions as well as to performance scores. This

® nding contradicted the predictions of the visual per-

ception perspective that slow-motion displays convey

intact relative motion information. However, further

work is required to determine whether the eþ ect of the

speed of visual demonstrations on action perception and

reproduction is a function of task constraints, such as

the novelty of relative motion corresponding to the

demonstrated activity. The more unfamiliar the relative

motion patterns used in task performance, the more

likely that the perception of optimal relative motion

will be hindered by slow-motion presentation. However,

this implication awaits further research before precise

suggestions for the use of slow-motion videotapes

in motor skill acquisition can be advanced. It could

be the case that slow-motion demonstrations are more

eþ ective at later stages of learning after the movement

percept and coordination functions underlying the task

have been established. In other words, slow-motion

presentations m ight be better used at more advanced

stages of learning to direct learners’ attention to some

speci® c aspects of performance, particularly in motor

skills with many sub-components varying in temporal

parameters.

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