spring 2006human performance 1h2 dr. c. baber 1 human performance 1h2 chris baber
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Spring 2006 Human Performance 1H2Dr. C. Baber
1
Human Performance
1H2
Chris Baber
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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
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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
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Report Marking SchemeSummary 10Introduction
Rationale 5Review 15Hypothesis 5
Method 25Results 15Conclusions 20References 5
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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.
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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
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Session One:
Working Assumptions about using Devices (from
1H1)
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User centred design
• ‘User’ as focus of design
• Actual user can be observed or questioned
• ‘Models’ of use can be created
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Requirements for model
• Capture everyday behaviour;
• Predict consequences of design;
• Guide design concept and evaluation;
• Explain problems and errors
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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)
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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
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Exercise #1
• Use the Seven Stage model to represent the activities associated with withdrawing £20 from a cashpoint machine
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Session Two:
Solving Problems
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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
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Exercise #2
Join all of the dots
Using a single line
DO NOT lift your penoff the paper
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Conclusion
• More than one solution
• Solution limited by boundary conditions
• Active involvement and testing
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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
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Conclusion
• Means-ends analysis:
To modify representationBreak problem into subproblemsTo test hypothesis through ‘trial and error’
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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’?
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Describing Problem Solving
• Initial State• Goal State• All possible intervening states
– Problem Space
• Path Constraints• State Action Tree
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Key issues
• Insight in some problems– Framing– Recognition of ‘affordances’
• Reframing of problem • Through representation• Through changing states• Through analogy
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Using Analogy
• Target problem• Analogue source• Surface similarities
– Same sort of objects
• Structural similarities– Common features or organisation
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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.
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Analogue Solution
• Rather than a single source, use multiple sources
• Triangulate low dose sources onto single spot
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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
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Session Three:
Knowledge in the head versus knowledge in the
world
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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
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Knowledge in the World:
external representations and cognitive artefacts
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Mapping
• Naturalness– Related to directness of mapping– Related to expertise / familiarity
• Appropriateness– Information should be appropriate to
the task (neither more nor less)
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Compatibility (see 1H1 notes)
• Direction of motion stereotypes• Affordance• S-R compatibility• S-C-R compatibility
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Artefacts & Representation
• Surface representation– Display and maintenance of symbols
on a visible surface
• Internal representation– Storage and organisation of symbols
• External representation
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‘Things that make us smart’
• Cognitive Artefacts used to assist everyday activity– Shopping List– Knotted handkerchief– Calculator– Diary
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Using an Abacus for Addition
6 + 2 = 8
Heaven beads = 5 each
Earth beads = 1 each
8 + 2 = 10
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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
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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?
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Cognitive Artefacts
• Distribute actions across time– Pre-computation
• Distribute actions across actors– Distributed cognition
• Change actions required
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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
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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
4. Nautical Slide Rule
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Calculating Ships Speed
• Knowledge-in-the-World– Nautical slide rule
• Replace calculation with manipulation
– Colleagues• Draw upon experience of others• Teamwork
– Plotter– Bearing taker– Bearing timer-recorder
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Calculating Noise Exposure
LEP,d = log ftot. + 90
0.1
dB(A)
f = t antilog [0.1 (L – 90)]
8
Nomogram versus Calculation
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Knowledge in the Head:notions of internal
representation
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Semantic Networks
ANIMAL
Has SkinCan moveEatsBreathes
BIRDCan fly
Has WingsHas feathers
FISHHas finsCan swimHas gillsCANARY
Is YellowCan sing
Collins & Quillian, 1969
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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
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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
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Exercise # 5
Define a chair
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Concepts
• How do you know a chair is a chair?
A chair has four legs…does it? A chair has a seat…does it?
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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
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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
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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
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CD Player
5-63-40-2
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Propositional Network
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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
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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
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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’
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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
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Mental Models
• Partial
• Procedures, Functions or System?
• Memory or Reconstruction?
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Session Five:
Perception
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Data-driven perception
Activation of neural structures of sensory system by pattern of stimulation from environment
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Theory-driven perception
Perception driven by memories and expectations about incoming information.
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KEYPOINT
PERCEPTION involves a set of active processes that impose:
STRUCTURE, STABILITY,
and MEANING on the world
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Visual Illusions
Old Woman or Young girl?
Rabbit or duck?
http://www.genesishci.com/illusions2.htm
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Exercise # 7
x
i. X on outside front cornerii. X on insideback corner
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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
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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
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‘Designed’ to confuse?
Push the start button…
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‘Designed’ to confuse?
the start button…
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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
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Primal Sketch Processes
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2½D Sketch
• Figure-ground segregation• Determine foreground and background
• Depth perception– Monocular
• Linear perspective• Texture gradients
– Binocular• Motion parallax• Correspondence and Convergence
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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
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Pandemonium:a model of featureextraction[Lindsay and Norman, 1977]
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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
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Reading
• Saccades and Fixations
• Anticipation and Inferences
• Interpretation
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Saccades and Fixations
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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]
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Buffers & Times for Reading
ms0 100 200 300
400Photoreceptor stimulationIconic memoryConceptual bufferArticulatory loopVisual spatial scratch padCentral executiveArticulation
From Kintsch, W., 1998, Comprehension
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Model of reading activityVisual stimulus
VisualAnalysis
VpresGrapheme-phonemeCorrespondence rules
ApresMentallexicon
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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
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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.”
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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]
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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.
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Inference and Recall
• Thorndyke (1976): recall of sentences from ‘Mary’ story– 85% correct sentence– 58% correct inference –
• sentence not presented
– 6% incorrect inference
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Session Five:
Attention
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Stroop Task
name the colours in which these words are printed as quickly as possible
Stroop, 1935
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Yellow
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Blue
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Red
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Green
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Blue
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Yellow
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Green
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Conclusion
Reading words vs Naming colours:
INTERFERENCE
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Automatic vs Controlled
• Automatic Processes are highly autonomous;
• Controlled Processes require conscious effort, i.e., need us to pay attention
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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
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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
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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
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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
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Early Selection:Broadbent (1958)
S1
S2
Limited Capacity Processing:
ignore ‘other' channel
Ring tone:Altering,Distracting
Selection based on physical
properties of stimulus
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Iconic MemorySperling (1960)
B F H K
D C J M
T R P N
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Iconic MemorySperling (1960)
B F H K
D C J M
T R P N
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Iconic MemorySperling (1960)
% items reported100
50
0
0 250 500 T (ms)
Whole report
Partialreport
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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
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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
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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
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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
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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
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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
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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
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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 (
%)
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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*
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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
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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
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Automaticity
• Norman and Shallice (1980)• Fully automatic processing controlled by
SCHEMATA
• Partially automatic processing controlled by either Contention Scheduling
• Supervisory Attentional System (SAS)
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Supervisory Attentional System Model
Perceptual System
SupervisoryAttentional
System
Effector System
Contentionscheduling
Triggerdatabase
Control schema
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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
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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.
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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
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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
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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
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POC
• Data limited • Resource limited
Cost
Task A
Task B
P
M Task A
Task B
P
MCost
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Session Five:
Memory
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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?
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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
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Recall
• Generate possible items, decide appropriateness
• Direct match between information available and long-term memory
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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
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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)
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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
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Long Term Memory
• Procedural – Knowing how
• Declarative– Knowing that
• Episodic vs. Semantic– Personal events– Language and knowledge of world
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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
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Declarative memory
• Knowledge for ‘facts’
• How is this knowledge organised?
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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
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ACT*
Declarativememory
Proceduralmemory
Working memory
Retrieval Storage Match Execution
OUTSIDE WORLD
Encoding Performance
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Retrieval from LTM
• Forgetting
• Recall vs. Recognition
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Forgetting
• Encoding failure– Failure of consolidation
• Storage failure– Disruption by new or existing
information– Associative interference
• Two responses associated with same stimulus
• Retrieval failure
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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
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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
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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
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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
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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.
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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.
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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.
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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
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Central executive
Articulatory control process
Auditory word presentation
Visual word presentation
Phonological store
Visual Cache
Inner scribe
Baddeley’s (1986) Model of Working Memory
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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
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Cowan (1999) Embedded Processes Model of Working Memory
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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
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Cowan’s (1995) model
• Working memory mechanism for activation of relevant long-term memory and for directing attention
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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
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Session Four:
Skill&
Expertise
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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
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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
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Reaction Time• Time to respond to a stimulus
– Speed-accuracy trade-off– Proficiency requires response on time
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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
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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
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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
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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
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Feedback
• Prior to action– Anticipation / prompts
• During action– Intrinsic
• Kinaesthetic• Proprioception
– Extrinsic
• Post action– Knowledge of results
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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
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Salthouse (1986)
• Input– Text converted to chunks
• Parsing– Chunks decomposed to strings
• Translation– Strings into characters and linked to
movements
• Execution– Key pressed
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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
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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
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Conclusions
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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.
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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
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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
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Key point # 3
PERCEPTION involves a set of active processes that impose:
STRUCTURE, STABILITY,
and MEANING on the world
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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
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Supervisory Attentional System Model
Perceptual System
SupervisoryAttentional
System
Effector System
Contentionscheduling
Triggerdatabase
Control schema
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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
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Working Memory
Phonological Loop
Auditory word presentationVisual word presentationArticulatory programmes
Visuo-spatial scratchpad
Central Executive
Visual cacheInner scribe
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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
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Solutions to Exercisesand Problems
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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’
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Problem #1
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Problem # 2
2.6414)37
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Problem#3
9567 + 1085
10652
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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?
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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
• Make a note of the word numbers and enter into table
• What pattern do you notice in the words?• Did you do as well as with the first list?
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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
• Make a note of the word numbers and enter into table
• Did you do as well as with the other lists?