spring 2006human performance 1h2 dr. c. baber 1 human performance 1h2 chris baber

Spring 2006 Human Performance 1H2Dr. C. Baber

1

Human Performance

1H2

Chris Baber


2

Lectures & LabsLectures:

Thursday 1-3 room 123

Labs:Weeks 4-10Friday mornings data collection exercises

• Each data collection exercise running over three week period

• Each session will involve group work


3

Assessment

• Course-work (50%)– ONE lab report (45%)

• 2500 words• to be handed in THURSDAY week 11• to describe data collection and apply principles

from lectures

– Attendance of sessions (5%)

• Examination (50%)– 2 questions from 3– 1½ hours


4

Report Marking SchemeSummary 10Introduction

Rationale 5Review 15Hypothesis 5

Method 25Results 15Conclusions 20References 5


5

Module Objectives

• Relate cognitive psychology to human-centred system design;

• Employ basic concepts from cognitive psychology;

• Describe the use of products in terms of the requisite cognitive activities.


6

Reading ListNorman, D.A.

The Design of Everyday ThingsNew York: Basic Books, 1990

http://www.baddesigns.com/index.shtml

Noyes, J.M. and Baber, C. User-Centred Design of SystemsBerlin: Springer-Verlag, 1999

Smyth, M.M. et al. Cognition in ActionLondon: LEA, 1987

Matthews, G., Davies, D.R., Westerman, S.J. and Stammers, R.B.,Human PerformanceLondon: Psychology Press, 2000

Wickens, C.D.Engineering Psychology and Human Performance,New York: Harper Collins, 1992




7

Session One:

Working Assumptions about using Devices (from

1H1)


8

User centred design

• ‘User’ as focus of design

• Actual user can be observed or questioned

• ‘Models’ of use can be created


9

Requirements for model

• Capture everyday behaviour;

• Predict consequences of design;

• Guide design concept and evaluation;

• Explain problems and errors


10

Assumptions

• Much of everyday behaviour is “automatic”– Requires little conscious control– Involves learned routines– Involves expectation (based on

previous experience)– Is error-free (or at least, error-

recoverable)– Is ‘skilled’ (i.e., well-practised)


11

Seven Stage Action Model[Norman, 1990]

Form intentionDevelop plan

Perform action

Object in world

Evaluate against goalInterpret object

Perceive state of object

GOAL OF PERSON


12

Exercise #1

• Use the Seven Stage model to represent the activities associated with withdrawing £20 from a cashpoint machine


13

Session Two:

Solving Problems


14

Problem Solving• A problem is something that doesn’t solve easily

• A problem doesn’t solve easily because:– you don’t have the necessary knowledge or,– you have misrepresented part of the problem

• If at first you don’t succeed, try something else

• Tackle one part of the problem and other parts may fall into place


15

Exercise #2

Join all of the dots

Using a single line

DO NOT lift your penoff the paper


16

Conclusion

• More than one solution

• Solution limited by boundary conditions

• Active involvement and testing


17

Exercise #3

XXXVII ÷ XIV

XXXX ÷ X

• Representation affects strategy– Convert from Roman to Arabic

• Strategy developed for one version might be inefficient in another version– Convert numerals or just ‘see’ 4


18

Conclusion

• Means-ends analysis:

To modify representationBreak problem into subproblemsTo test hypothesis through ‘trial and error’


19

SUDOKU analysis

• From the verbal protocols:– How many times did the person refer

to the ‘rules’?– How many times did the current

version of the problem constrain their choice?

– How many times did they act in terms of ‘trial and error’?


20

Describing Problem Solving

• Initial State• Goal State• All possible intervening states

– Problem Space

• Path Constraints• State Action Tree


21

Key issues

• Insight in some problems– Framing– Recognition of ‘affordances’

• Reframing of problem • Through representation• Through changing states• Through analogy


22

Using Analogy

• Target problem• Analogue source• Surface similarities

– Same sort of objects

• Structural similarities– Common features or organisation


23

Using AnalogyYou are a doctor faced with a patient who has a malignant growth in his stomach. It is impossible to operate on the patient, but the growth needs to be treated. There is a ray you can use. If the ray is strong enough it can destroy the growth. However if the ray is too strong is can also destroy tissue. If the ray is too weak it will not affect the growth.

A fortress is located in the centre of the country. Many roads radiate from the fortress. You want to capture the fortress. The roads might be mined, so you can’t attack on one road without risk of losing all of your troops. However an attack by one group is not enough and you need to attack with all of your troops.


24

Analogue Solution

• Rather than a single source, use multiple sources

• Triangulate low dose sources onto single spot


25

Expert Problem Solving

• Expert performance in problem solving can differ from novices:– More knowledge about particular field– Knowledge organised differently– Problems features recognised differently,

e.g., inclined planes vs. conservation of energy

– More time on analysing problem– Performance outside field similar to novices


26

Session Three:

Knowledge in the head versus knowledge in the

world


27

Knowledge in the HeadKnowledge in the World

“Menus relieve users of the need to remember command names, but not of the need to know what functions can be performed by some commands…”

[Mayes et al., 1988]

Knowledge held by users and recalled‘Knowledge’ prompted by objects in world


28

Knowledge in the World:

external representations and cognitive artefacts


29

Mapping

• Naturalness– Related to directness of mapping– Related to expertise / familiarity

• Appropriateness– Information should be appropriate to

the task (neither more nor less)


30

Compatibility (see 1H1 notes)

• Direction of motion stereotypes• Affordance• S-R compatibility• S-C-R compatibility


31

Artefacts & Representation

• Surface representation– Display and maintenance of symbols

on a visible surface

• Internal representation– Storage and organisation of symbols

• External representation


32

‘Things that make us smart’

• Cognitive Artefacts used to assist everyday activity– Shopping List– Knotted handkerchief– Calculator– Diary


33

Using an Abacus for Addition

6 + 2 = 8

Heaven beads = 5 each

Earth beads = 1 each

8 + 2 = 10


34

Shopping Lists

• Construct list– Using the process of writing the list to

support decision making• Remember to consult list

– Check the list during shopping– Use the list to help navigate the store

• Reading and interpret list– Make sure everything is bought


35

Shopping Lists

• Memory aid– Do we only buy what’s on the list?– Do we buy items not on the list?

• Additional tasks– Does writing the list create a new task?

• Modified task– Does using the list change the way we shop?


36

Cognitive Artefacts

• Distribute actions across time– Pre-computation

• Distribute actions across actors– Distributed cognition

• Change actions required


37

Calculating Ships Speed

1. D=RT, (R=D/T) using pencil and paper

2. D=RT, using calculator3. 3-minute rule:

3-minutes = 1/20 of an hour, and 100yds in 1/20 of a nautical mile 1500 yds in 3 minutes = 15nmph


38


1. D=RT, (R=D/T) using pencil and paper

2. D=RT, using calculator3. 3-minute rule:

3-minutes = 1/20 of an hour, and 100yds in 1/20 of a nautical mile 1500 yds in 3 minutes = 15nmph

4. Nautical Slide Rule


39


• Knowledge-in-the-World– Nautical slide rule

• Replace calculation with manipulation

– Colleagues• Draw upon experience of others• Teamwork

– Plotter– Bearing taker– Bearing timer-recorder


40

Calculating Noise Exposure

LEP,d = log ftot. + 90

0.1

dB(A)

f = t antilog [0.1 (L – 90)]

8

Nomogram versus Calculation


41

Knowledge in the Head:notions of internal

representation


42

Semantic Networks

ANIMAL

Has SkinCan moveEatsBreathes

BIRDCan fly

Has WingsHas feathers

FISHHas finsCan swimHas gillsCANARY

Is YellowCan sing

Collins & Quillian, 1969


43

Levels and Reaction time

A canary is a canary

A canary is a bird

A canary is an animal

A canary is a fish

A canary can sing

A canary can fly

A canary has skin

A canary has gills

Collins & Quillian, 1969

0.9

1

1.1

1.2

1.3

1.4

1.5

0 1 2 False

Levels of Sentences

Mean

Reacti

on

Tim

e (

s)

Property

Category


44

Canaries

• Different times to verify the statements:– A canary is a bird– A canary can fly– A canary can sing

• Time proportional to movement through network


45

Exercise # 5

Define a chair


46

Concepts

• How do you know a chair is a chair?

A chair has four legs…does it? A chair has a seat…does it?

http://images.google.co.uk/imgres?imgurl=http://www.rybo.no/images/balans/easy2-l.gif&imgrefurl=http://www.rybo.no/english/ba-easy.htm&h=148&w=174&sz=5&tbnid=waslQ5kt-OoJ:&tbnh=79&tbnw=94&start=7&prev=/images%3Fq%3Dbalans%2Bchair%26hl%3Den%26lr%3D%26sa%3DG


47

Exercise # 6

On a scale of 1 (typical) to 7 (atypical), rate the following as examples of the concept: FURNITURE

Chair CurtainsSewing Machine DeskSofa TableTelephone VaseDresser FanClock Cooker


48

Prototypes, Typical Features, and Exemplars

• Prototype• ROSCH (1973): people do not use feature sets,

but imagine a PROTOTYPE for an object

• Typical Features• ROSCH & MERVIS (1975): people use a list of

features, weighted in terms of CUE VALIDITY

• Exemplars• SMITH & MEDIN (1981): people use an EXAMPLE

to imagine an object


49

Representing Concepts

• BARSALOU (1983)– TAXONOMIC

• Categories that are well known and can be recalled consistently and reliably

– E.g., Fruit, Furniture, Animals• Used to generate overall representation of the

world

– AD HOC• Categories that are invented for specific purpose

– E.g., How to make friends, Moving house• Used for goal-directed activity within specific

event frames


50

CD Player

5-63-40-2


51

Propositional Network


52

Problems with Semantic and Propositional

networks• Propositions do not have equal weight

– Salmon: is pink / has fins

• Some items are more representative than others– Is bird: Robin / Ibis

• Some concepts do not have unequivocal defining attributes, e.g., ‘game’

• Some items are ‘fuzzy– Is furniture: Chair / Book-end

• Position in hierarchy does not always correspond to speed of response


53

Mental models

• Craik– Internal representation of external

reality– Every good monitor needs a model of

the world it is monitoring

• Johnson-Laird– Strategies of knowledge assimilation


54

Mental Models

• Van Dijk and Kintsch (1983)– Text processed to extract propositions,

which are held in working memory;– When sufficient propositions in WM,

then linking performed;– Relevance of propositions to linking

proportional to recall;– Linking reveals ‘gist’


55

Scripts, Schema and Frames

• Schema = chunks of knowledge– Slots for information: fixed, default, optional

• Scripts = action sequences– Generalised event schema (Nelson, 1986)

• Frames = knowledge about the properties of things


56

Mental Models

• Partial

• Procedures, Functions or System?

• Memory or Reconstruction?


57

Session Five:

Perception


58

Data-driven perception

Activation of neural structures of sensory system by pattern of stimulation from environment


59

Theory-driven perception

Perception driven by memories and expectations about incoming information.


60

KEYPOINT

PERCEPTION involves a set of active processes that impose:

STRUCTURE, STABILITY,

and MEANING on the world


61

Visual Illusions

Old Woman or Young girl?

Rabbit or duck?

http://www.genesishci.com/illusions2.htm


62

Exercise # 7

x

i. X on outside front cornerii. X on insideback corner


63

Exercise # 7

• Work on pairs: Participant + Observer

• Participant Reverse X as fast as possible (say ‘Reverse’ each time). Observer mark each reverse

• Participant Fix X as front (say ‘Reverse’ if X moves). Observer mark each reverse


64

KEYPOINT

• Perception limits are set by sensory / neural mechanisms; but beyond these limits, perception can be cognitively controlled;

• Sensory experiences interpreted in a CONTEXT and derive from a variety of sources


65

‘Designed’ to confuse?

Push the start button…


66

‘Designed’ to confuse?

the start button…


67

Marr’s theory of visual perception

• Primal Sketch• Viewer Centred Representation using basic

perceptual properties, e.g., edges, length, contrast, contour

• 2½D Sketch• Viewer Centred Representation using shading,

texture, depth cues, figure-ground discrimination

• 3D Sketch• Object Centred Representation using structural

description of object independent of viewpoint


68

Primal Sketch Processes


69

2½D Sketch

• Figure-ground segregation• Determine foreground and background

• Depth perception– Monocular

• Linear perspective• Texture gradients

– Binocular• Motion parallax• Correspondence and Convergence


70

Contrast EffectsThis text is quite easy to read because the contrast between figure and ground is high

This text is more difficult to read because the contrast between figure and ground is lower

This text is very hard to read because the contrast between figure and ground is minimal


71

Pandemonium:a model of featureextraction[Lindsay and Norman, 1977]


72

KEYPOINT

• The design of displayed information INFLUENCES how the user can use that information;

• The design of displayed information should support EXTRACTION of relevant information


73

Reading

• Saccades and Fixations

• Anticipation and Inferences

• Interpretation


74

Saccades and Fixations


75

Times for Normal Readers

• Reading speed: 180 – 350 wpm• Saccade: 40ms• Return sweep: 55ms• Fixation: 330ms • 64% of words fixated• Perceptual span:

[4 letters] X [12 letters]


76

Buffers & Times for Reading

ms0 100 200 300

400Photoreceptor stimulationIconic memoryConceptual bufferArticulatory loopVisual spatial scratch padCentral executiveArticulation

From Kintsch, W., 1998, Comprehension


77

Model of reading activityVisual stimulus

VisualAnalysis

VpresGrapheme-phonemeCorrespondence rules

ApresMentallexicon


78

Interpretation

Knowledge of what you are “looking at” can aid in interpretation

JA CKAN DJI LLW ENTU PTH EHI LLT OFETCH APA ILOFWA TER

Organisation of information is also useful


79

Story Grammars

• Analogy with sentence grammars– Building blocks and rules for

combining

• Break story into propositions

“Margie was holding tightly to the string of her beautiful new balloon. Suddenly a gust of wind caught it, and carried it into a tree. It hit a branch, and burst. Margie cried and cried.”


80

Story GrammarStory

Setting Episode

Event

Reaction

Internal response

Overt response

ChangeOf state

Event

Event

Event

Event Event Event [sadness]

[1]

[2] [3] [4]

[5]

[6]


81

Inferences

• Comprehension typically requires our active involvement in order to supply information which is not explicit in the text

1. Mary heard the ice-cream van coming2. She remembered her pocket money3. She rushed into the house.


82

Inference and Recall

• Thorndyke (1976): recall of sentences from ‘Mary’ story– 85% correct sentence– 58% correct inference –

• sentence not presented

– 6% incorrect inference


83

Session Five:

Attention


84

Stroop Task

name the colours in which these words are printed as quickly as possible

Stroop, 1935


85

Yellow


86

Blue


87

Red


88

Green


89

Blue


90

Yellow


91

Green


92

Conclusion

Reading words vs Naming colours:

INTERFERENCE


93

Automatic vs Controlled

• Automatic Processes are highly autonomous;

• Controlled Processes require conscious effort, i.e., need us to pay attention


94

Topics relating to attention

A udit or y

shadowing

V isual

S pot l ight

F ocused A t t ent ion

pr ocess only one input

T ask s imilar it y T ask D iffi cult y Pr act ice

D ivided at t ent ion,

pr ocess al l input s

A T T E N T I O N

Eysenck and Keane, 1990


95

Focused Attention

• Focused Attention:– Present two stimuli and only respond to

one• How can we follow one conversation

when several people are speaking at once? (e.g., at a party)

• Physical characteristics of message:– Intensity of voice, gender of speaker


96

Shadowing

Listen to one message to each ear. Repeat back one message and ignore the other

– listeners could not report the language used in the non-attended message

– Listeners could not report content of the non-attended message even when words repeated 35 times each

– BUT if a tone was inserted into the non-attended message, listeners would notice it


97

Models of Selection

Sensory register

Selectivefilter Perceptual

processShort term memory

Broadbent

Triesman

Deutsch and Deutsch

Sensory register

Attenuationcontrol

Perceptual process

Short term memory

Sensory register

Selectivefilter

Perceptual process

Short term memory


98

Early Selection:Broadbent (1958)

S1

S2

Limited Capacity Processing:

ignore ‘other' channel

Ring tone:Altering,Distracting

Selection based on physical

properties of stimulus


99

Iconic MemorySperling (1960)

B F H K

D C J M

T R P N


100


B F H K

D C J M

T R P N


101


% items reported100

50

0

0 250 500 T (ms)

Whole report

Partialreport


102

Problems with Early Selection

•Gray and Wedderburn (1960)

Left ear Right ear6 AUNT 3 DEAR 8 JANE

Should report Left ear then Right ear, but participants reported Words then Numbers


103

Attenuation:Treisman (1964)

• People do not ignore ‘unattended’ channel

• All information undergoes superficial semantic analysis to determine relevance

• If information not relevant, then processing attenuated


104

Unattended Channel?

• Cherry (1953) claimed people do not attend to ‘other’ channel, Treisman (1964) claims they do.

• Cherry – off-line measurement• Participants asked to report at the end of study

• Treisman – on-line measurement• Participants asked to report during study.• Reporting only occurs when short time between

listening and report, i.e., a few seconds


105

Space-based Theories of Attention

• spotlight metaphor• 0.5 degree minimal constriction• Loss of efficiency with size• Circular shape• Single spotlight (but can be divided into

two)• Functions most effectively with fixation


106

Contemporary theories of attention

• Object-based theories:• People can select one of two overlapping

objects

– Neisser• Selection guided by Schema, following a

Perceptual Cycle

– Humphreys: • Attentional Engagement theory

– Perceptual description => visual short term store


107

Subliminal Adverts• Canadian cinema goers had ‘Drink Coke’ and ‘Eat

popcorn’ spliced into film – sales increased

• In 1990s:– Study One: participants shown spliced film and reported

being more hungry / thirsty than control– Study Two: same results – only message said ‘Phone now’

• See also ‘self-help’ tapes, e.g., 50% of listeners in one study felt their memory had improved, but has listened to a different tape


108

Divided Attention

• Dual tasks require people to divide attention

• Limited attentional resource that is shared between tasks

• Depends on tasks, e.g., talk and drive, sight read music and shadow speech


109

Allport et al. (1972)• Participants presented with essay, either visual

and auditory• Recognition test far worse with auditory

0

10

20

30

40

50

Pictures Visual

Words

Auditory

Words

Control

Experiment

Err

ors

in R

eco

gnit

ion (

%)


110

Brooks (1968)Imagine ‘F’ with * moving around edge

When * reaches junction or end, indicate Y (end) or N (junction)

Verbal – say Yes or NoTapping – tap once for Y and twice

for NPointing – point to next Y or N in list

V = T < PIndicating selective interference

F*


111

Task Similarity• Interference when use same stimulus modality –

visual or auditory

• Interference when use same stage of processing – input: central: output

• Interference when use same memory codes – verbal or visual

• Interference when use same response codes – spoken or manual


112

Practice and Expertise

– Highly practised dual-task performance, e.g., 6 weeks read + take dictation

– Expert pianists can sight-read + shadow; expert typists can touch-type + shadow

• Performance strategies• Reduced demand• Reduced resource load


113

Automaticity

• Norman and Shallice (1980)• Fully automatic processing controlled by

SCHEMATA

• Partially automatic processing controlled by either Contention Scheduling

• Supervisory Attentional System (SAS)


114

Supervisory Attentional System Model

Perceptual System

SupervisoryAttentional

System

Effector System

Contentionscheduling

Triggerdatabase

Control schema


115

Contention Scheduling• Gear changing when driving involves many

routine activities but is performed ‘automatically’ – without conscious awareness

• When routines clash, relative importance is used to determine which to perform – Contention Scheduling

• e.g., right foot on brake or clutch


116

SAS activation

• Driving on roundabouts in France– Inhibit ‘look right’; Activate ‘look left’– SAS to over-ride habitual actions

• SAS active when:• Danger, Choice of response, Novelty etc.


117

Attentional Slips and Lapses

• Habitual actions become automatic• SAS inhibits habit• Perserveration

• When SAS does not inhibit and habit proceeds

• Distraction• Irrelevant objects attract attention• Utilisation behaviour: patients with frontal lobe

damage will reach for object close to hand even when told not to


118

Performance Operating Characteristics

• Resource-dependent trade-off between performance levels on two tasks

• Task A and Task B performed several times, with instructions to allocate more effort to one task or the other


119

Task Difficulty

• Data limited processes• Performance related to quality of data

and will not improve with more resource

• Resource limited processes• Performance related to amount of

resource invested in task and will improve with more resource


120

POC

• Data limited • Resource limited

Cost

Task A

Task B

P

M Task A

Task B

P

MCost


121

Session Five:

Memory


122

What is ‘memory’?

• Is memory a permanent store of everything we know?– Why do we forget?– Why do we make mistakes when

trying to remember something?– Why do we find we can’t remember

something and then suddenly remember it much later?


123

Recognition vs Recall

• Recall– Retrieve from memory

• Remembering the correct ‘print’ command

• Recognise– To bring back into awareness through

prompt• Recognising print icon• Recognising print item in menu


124

Recall

• Generate possible items, decide appropriateness

• Direct match between information available and long-term memory


125

2 x 2 processes?

• Contemporary thinking on recall / recognition implies at least two recall processes and at least two recognition processes

• Selection of which process could reflect choice of STRATEGY


126

Recognition

• Familiarity– Intra-item organisation– Effects ‘sense’ of being to remember

• Identification– Retrieval process

• Recognition memory better for rare words than for common words (Gregg, 1976)


127

Encoding Specificity Principle

• Recall and recognition different effects of same retrieval process

• Retrieval depends on overlap between features in memory and features in retrieval environment

• Vary Interactive context: – Recall < Cued recall < Recognition


128

Long Term Memory

• Procedural – Knowing how

• Declarative– Knowing that

• Episodic vs. Semantic– Personal events– Language and knowledge of world


129

Production Systems

• Knowing how to do X– Production rule = set of conditions

and an action

IF it is rainingAnd you wish to go out

THEN pick up your umbrella


130

Declarative memory

• Knowledge for ‘facts’

• How is this knowledge organised?


131

Adaptive Control of Thought (ACT)

• Network of propositions

• Production rules selected via pattern matching

• If information in working memory matches production rule condition, then fire production rule


132

ACT*

Declarativememory

Proceduralmemory

Working memory

Retrieval Storage Match Execution

OUTSIDE WORLD

Encoding Performance


133

Retrieval from LTM

• Forgetting

• Recall vs. Recognition


134

Forgetting

• Encoding failure– Failure of consolidation

• Storage failure– Disruption by new or existing

information– Associative interference

• Two responses associated with same stimulus

• Retrieval failure


135

Retrieval Failure

• Context• Intrinsic / Interactive: integral to stimulus• Extrinsic / Non-interactive: appear during

presentation but not part of stimulus

• Environment• Classroom learning affected when testing took

place in different room and reduced further in presence of different teacher

• State• Affect of drugs on memory task show:

– Affect for free-recall when matched– No affect for cued recall or recognition


136

Amnesia [1]

• Infantile amnesia• Inability to remember events from before aged 4

years

• Anterograde amnesia• Inability to remember new information• HM learnt handful of words since 1950

• Retrograde amnesia• Inability to remember events from just before

injury / illness• Ribot’s law: person aged 60 can remember

childhood events and early adult life, but increasingly vague for later life


137

Amnesia [2]

• Evidence that declarative knowledge affected but procedural knowledge intact

• Amnesiacs find it difficult to form new episodic or semantic memories

• Amnesiacs often acquire motor skills as fast as normals


138

Exercise # 3Word # List 1 List 2 List 3

19-20

17-18

15-16

13-14

11-12

9-10

7-8

5-6

3-4

0-2


139

Exercise # 3.1

• I will read a list of 20 words, when I have finished, write down as many as you can remember. You can write the words down in any order.


140

Exercise # 3.2

• I will read a list of 20 words, when I have finished write down as many as you can. You can write the words down in any order.


141

Exercise # 3.3

• I will give you a number, when you hear the number begin to count backwards in 3s, e.g., 99 – 96 – 93, as quickly as you can. I will read a list of 20 words, when I have finished write down as many as you can. Do not stop counting in 3s. Write down the number you got to.


142

Working Memory• Limited Capacity

• 7 + 2 items (Miller, 1965)• 4 + 2 chunks (Broadbent, 1972)• Modality dependent capacity

• Strategies for coping with limitation• Chunking• Interference• Activation of Long-term memory


143

Central executive

Articulatory control process

Auditory word presentation

Visual word presentation

Phonological store

Visual Cache

Inner scribe

Baddeley’s (1986) Model of Working Memory


144

Slave Systems

• Articulatory loop– Memory Activation– Rehearsal capacity

• Word length effect and Rehearsal speed

• Visual cache– Visual patterns– Complexity of pattern, number of elements etc

• Inner scribe– Sequences of movement– Complexity of movement


145

Cowan (1999) Embedded Processes Model of Working Memory


146

Schematic of Cowan’s (1995)

embedded processes model Central Executive

Brief sensory store

Activated memory

Long-term store

Focus of

attention Automatic action

Controlled action


147

Cowan’s (1995) model

• Working memory mechanism for activation of relevant long-term memory and for directing attention


148

Keypoint # 6

• Working memory is a volatile storage medium.

• Do not expect people to remember complex information, particularly if they are doing something else at the same time.

• Design information to keep within memory limits, e.g., no more than 9 items to a list


149

Session Four:

Skill&

Expertise


150

Varieties of Skill

• Simple vs. Complex – Type of task

• Physical vs. Cognitive– Demands and resources

• Open vs. Closed Loop– Interaction with stimuli

• Controlled vs. Automatic– Demands on attentional capacity


151

Classification of skills Holding (1989)

Simple

Complex

Open(Perceptual,Controlled,

Skilled)

Closed(Motor,

Habitual,Automatic)

DECISION

VIGILANCE

TRACKING

TAPPING

detection sorting shot-putting

ATC violin sleight-of-hand

football piloting

sailing

draughting ballet


152

Reaction Time• Time to respond to a stimulus

– Speed-accuracy trade-off– Proficiency requires response on time


153

Choice Reaction Time

• Hick-Hyman Law (1952)CRT = K log (n + 1)

CRT = choice reaction time, K = constant (equal to SRT), and n = number of alternatives

• Smith (1977)CRT = K log (n C/E + 1)

C = response emphasis ( c: speed or C: accuracy), E = strength of stimulus


154

Expert Reaction Time

• Timing requires anticipation of stimulus to offset response delay

• Skill as ability to anticipate events and to produce, quickly, appropriate chain of responses


155

Acquiring Skill

• Fitts (1962):– Cognitive phase:

• instructions and practice with knowledge of results

– Associative phase: • practice to criterion and self-monitoring

– Autonomous phase: • automated performance


156

Practice

• Skilled performance lacks asymptote– Physical limitations of task or decline in

capabilities, due to fatigue of ageing as limiting factors

• Thus, increased experience leads to increased performance– Goalkeeping relative to judging speed and

angle of shots rather than physical fitness– Professional snooker, darts or golf players

compete into their forties and beyond


157

Feedback

• Prior to action– Anticipation / prompts

• During action– Intrinsic

• Kinaesthetic• Proprioception

– Extrinsic

• Post action– Knowledge of results


158

Typing

• Eye-hand span related to expertise• Expert = 9, novice = 1

• Inter-key interval• Expert = 100ms

• Strategy• Hunt & Peck vs. Touch typing

• Keystroke• Novice = highly variable keystroke time• Novice = very slow on ‘unusual’ letters, e.g., X or

Z


159

Salthouse (1986)

• Input– Text converted to chunks

• Parsing– Chunks decomposed to strings

• Translation– Strings into characters and linked to

movements

• Execution– Key pressed


160

Rumelhart & Norman (1982)

• Perceptual processes – Perceive text, generate word schema

• Parsing– Compute codes for each letter

• Keypress schemata– Activate schema for letter-keypress

• Response activation– Press defined key through activation of

appropriate hand / finger


161

Schematic of Rumelhart and Norman’s connectionist model of

typingmiddle

ring indexlittle thumb

Left hand

middleindex ring

thumb little

Right hand

Response system

activation

j a z z

jazzWord node, activated fromVisual or auditory stimulus

Keypress node, breakingWord into typed letters;Excites and inhibits nodes


162

Conclusions


163

Key point # 1

A ‘User model for designers’ assumes that people actively seek information from the environment and develop expectations of how things work; these expectations influence the ways in which people seek information.


164

Schematic of Rumelhart and Norman’s connectionist model of

typingmiddle

ring indexlittle thumb

Left hand

middleindex ring

thumb little

Right hand

Response system

activation

j a z z

jazzWord node, activated fromVisual or auditory stimulus

Keypress node, breakingWord into typed letters;Excites and inhibits nodes


165

Keypoint # 2

• In order to learn the correct view, it is necessary to undo the incorrect view

• This means that acquiring new knowledge might mean effortfully removing erroneous, old knowledge


166

Key point # 3

PERCEPTION involves a set of active processes that impose:

STRUCTURE, STABILITY,

and MEANING on the world


167

Key point # 4

• Perception limits are set by sensory / neural mechanisms; but beyond these limits, perception can be cognitively controlled;

• Sensory experiences interpreted in a CONTEXT and derive from a variety of sources


168

Supervisory Attentional System Model

Perceptual System

SupervisoryAttentional

System

Effector System

Contentionscheduling

Triggerdatabase

Control schema


169

Key point # 5

• The design of displayed information INFLUENCES how the user can use that information;

• The design of displayed information should support EXTRACTION of relevant information


170

Working Memory

Phonological Loop

Auditory word presentationVisual word presentationArticulatory programmes

Visuo-spatial scratchpad

Central Executive

Visual cacheInner scribe


171

Keypoint # 6

• Working memory is a volatile storage medium.

• Do not expect people to remember complex information, particularly if they are doing something else at the same time.

• Design information to keep within memory limits, e.g., no more than 9 items to a list


172

Solutions to Exercisesand Problems


173

Exercise Two

I II III

1. Form goal Get cash; Access ATM

Get cash Obtain £20

2. Form Intention Gain access Select ‘Cash’ from menu

Select ’20’ from menu

3. Specify action Use card / PIN Select ‘Cash’ button

Select ’20’ button

4. Execute action Insert card; Enter PIN

Press button Press button

5. Perceive state of object Access granted Screen changes Screen changes

6. Interpret perception Read screen Read screen Read screen

7. Evaluate outcome of action

Find ‘Cash’ Define amount Decide ‘other service’


174

Problem #1


175

Problem # 2

2.6414)37


176

Problem#3

9567 + 1085

10652


177

Exercise #.1 1. Apple 2. North 3. Charlie 4. Nickel 5. Red 6. Banana 7. South 8. Fred 9. Cent 10. Green 11. Pear 12. East 13. George 14. Dime 15. Yellow 16. Grape 17. Wayne 18. Dave 19. Penny 20. Blue

• Make a note of the word numbers and enter into table

• How many people wrote: West or Orange?• What pattern do you notice in the words?


178

Exercise #.21. Latch 2. Bream 3. Hot 4. Mayor 5. Jab6. Busk 7. Else 8. Wage 9. Clog 10. Jowl 11. Chap 12. Big 13. Smug 14. Duck 15. Trout 16. Blot 17. Reek 18. Tape 19. List 20. Skirt


• What pattern do you notice in the words?• Did you do as well as with the first list?


179

Exercise #.31. Time 2. House 3. Mit 4. Stab 5. Solve6. Draft 7. Say 8. Off 9. Boil 10. Court 11. Greet 12. Slot 13. Hand 14. Dirt 15. Clot 16. Stale 17. Out 18. Dumped 19. Stone 20. Dice


• Did you do as well as with the other lists?

spring 2006human performance 1h2 dr. c. baber 1 human performance 1h2 chris baber

Documents

human performance london

1h1 slide

human centred system

group work slide

wellpractised slide

cashpoint machine slide

user centred design

cognitive psychology