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Human Performance

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Title: Human Performance


1
Human Performance 1H2
Chris Baber
2
Lectures Labs
  • Lectures
  • Thursday 2-4 room 521
  • Labs
  • Weeks 4-10
  • Friday 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)
  • 3000 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 Scheme
5
Module Objectives
  • At the end of this module, students will be
    expected to be able to
  • Relate principles of human information
    processing 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 List
  • Norman, D.A. , 1990, The Design of Everyday
    Things New York Basic Books
  • Noyes, J.M. and Baber, C. , 1999, User-Centred
    Design of Systems Berlin Springer-Verlag
  • Smyth, M.M. et al. , 1994, Cognition in Action
    London LEA 2nd edition
  • Matthews, G., Davies, D.R., Westerman, S.J. and
    Stammers, R.B., 2000, Human Performance London
    Psychology Press
  • Wickens, C.D. And Hollands, J., 1999, Engineering
    Psychology and Human Performance, New York
    Harper Collins

7
Session One Working Assumptionshow people
use technology
8
Affordance
  • See handle
  • Reach out hand
  • Grasp handle
  • Turn handle
  • Pull door

9
Using tools
  • Form Physical appearance
  • Function Sequence of activity
  • Experience Knowledge of use

10
The Cooker Problem 1
Which control acts on which ring?
11
The Cooker Problem 2
Which control acts on which ring?
12
Spatial Compatibility?
http//www.baddesigns.com/boombox.html
13
Direction of motion Stereotypes
c
1 2 3 4 5 6 7
a
d
?
?
1 2 3 4 5 6 7
b
Clockwise increase Clockwise right Clockwise
away from control Clockwise increase on scale
14
Clockwise to Increase?
7 6 5 4 3 2 1
15
Rule I to set time turn control Rule II to set
time lt 15s, turn control past 15s and then turn
back to desired time
http//www.baddesigns.com/timer.html
16
Make the freezer warmer without changing fresh
food setting
Normal settings C AND 5 Colder fresh
food C AND 6-7 1 Set both controls Coldest
fresh food B AND 8-9 2 Allow 24 hours to Warmest
fresh food D AND 7-8 stabilize Off (fresh fd
frz) C AND 4-1
7 6 5 4 3 2 1 fresh food
A B C D E freezer
Norman, D.A., 1990, The Design of Everyday
Things, New York Basic Books
17
1. Thermostat and control for each compartment,
hence two sets of controls(but why do the
controls interact?)2. Only one thermostat and
distribution of cold air varied between
compartments (but in which compartment is the
thermostat?)
Possible explanatory models...
18
Conclusions
  • We have learned routines for how to use many
    technologies
  • We apply these routines automatically
  • When the routines succeed, they are reinforced
  • When the routines fail, we shift from automatic
    to problem-solving activity

19
Rasmussens Skills, Rules, Knowledge model
Knowledge-based behaviour
Skill-based behaviour
Rule-based behaviour
20
Exercise 1
  • Use the SRK model to represent the activities
    associated with buying a can of drink from a
    vending machine
  • As skill-based beahviour
  • As rule-based behaviour
  • As knowledge-based behaviour

21
Session TwoSolving Problems
22
Problem Solving
  • A problem is something that doesnt solve easily
  • A problem doesnt solve easily because
  • you dont have the necessary knowledge or,
  • you have misrepresented part of the problem
  • If at first you dont succeed, try something else
  • Tackle one part of the problem and other parts
    may fall into place

23
Exercise 2
Move 3 dots to make the triangle point down
24
Framing as Representation
  • 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

25
Exercise 2
Move 3 dots to make the triangle point down
26
  • Complete grid by putting numbers into cells
  • RULES
  • Each number may appear only once in a 3x3 grid,
    or a row or a column
  • Each 3x3 grid, row and column must contain all
    the numbers from 1 to 9

27
SUDOKU analysis
  • Reflect on your performance
  • How many times did you refer to the rules?
  • What were the main heuristics you applied?
  • How many times did the current version of the
    problem constrain your choice?
  • How many times did you act in terms of trial and
    error?

28
Heuristics used in SUDUKO
  • Hidden loner
  • 1 in the centre block or 7 in the bottom
    right block because this is the only space for it
  • Locked candidates
  • Candidate number is restricted to one row or
    column, so removing a cell from the space

29
Constraint Programming
  • Enter all possible values and then eliminate when
    solutions are plausible
  • Back-tracking when errors found
  • Brute-force approach which can easily be coded

30
Verbal Protocol
  • A method that requires people to think-aloud
    when performing tasks
  • Assumes that people verbalise their thoughts
  • Keep the person talking
  • If they pause, ask what are you thinking now?
  • Practice work in pairs one person calculates 24
    x 36 ? the other prompts and records

31
Content Analysis
  • I need to multiply 24 by 36. So, start with the
    numbers in the units column, thats 4 times 6
    which is 24. So thats 4 carry 2. Then in the
    tens column, its 4 times 3 which is 12 and add
    the carried 2, which is 14. So the first row in
    the answer in 144. Then on the next row put a 0
    in the units column and do the tens. That would
    be 2 times 3, which is 12 so 2 on the second
    row and carry the 1. Then 2 times 3 is 6 and add
    the 1 is 7. So the second row is 720. Then add
    the um what was it? 144 and - the 720.
    That makes 4 and 6 and 8. So the answer is 864.
  • Remove function words (I, is, the, and...)
  • Coding Number, Operator, Store, Plan
  • need to multiply 24 36. start with numbers in
    units column 4 times 6 24. 4 carry 2. Then in
    tens column 4 times 3 12 add carried 2 14.
    first row in answer 144. on next row put a 0 in
    units column do tens. That would be 2 times 3
    12 2 on second row carry 1. Then 2 times 3 6
    add 1 7. So second row is 720. Then add 144
    720. That makes 4 6 8. So answer is 864.
  • PROCESS -gtmultiply number A by units part of B
  • -gt put result in 10s and units
  • -gt multiply number A by tens part of B
  • -gt put result in 10s and units
  • -gtadd results

32
Approaches to Solving Problems
  • Trial and Error
  • Knowledge only of possible actions, e.g.,
    navigating a maze
  • Hill Climbing
  • Knowledge of possible actions AND some way of
    deciding how close you are to your goal, e.g.,
    hobbits and orcs
  • Mean Ends Analysis
  • Knowledge of appropriate actions and selection of
    actions to lead to a goal

33
Exercise3 Water Jug Problem
  • Work in Pairs
  • One of you solve the problem and talk through
    your solution
  • One of you write down what your partner says and
    does

34
The Water Jug Problem
  • Goal Produce exactly 4 pints

Waste
5 pints
3 pints
35
Events, States, Actions, Rules
  • List the Events, States and Actions mentioned
  • Define these as Rules
  • Are these Rules sufficient to capture the task?
  • How do the Rules need to change to cope with (a)
    different size jugs and (b) different goals?

36
Defining a State Space
  • State space defined as ordered pairs (x,y) where
  • x 0, 1,2, 3,4, 5
  • y 0,1,2, 3
  • start state (0,0)
  • goal state is (4, n)

37
Production Rules for a solution
38
Breadth First Search Tree for Water Jug problem
(0,0)
(5,0)
(0,3)
(0,0)
(2,3)
(5,3)
(0,0)
(3,0)
(5,3)
39
Describing Problem Solving
  • Initial State
  • Goal State
  • All possible intervening states
  • Problem Space
  • Path Constraints
  • State Action Tree

40
Using Analogy
  • Target problem
  • Analogue source
  • Surface similarities
  • Same sort of objects
  • Structural similarities
  • Common features or organisation

41
Using Analogy
  • You 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 cant 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.

42
Conclusion
  • More than one solution
  • Solution limited by boundary conditions
  • Framing of problem
  • Through representation
  • Through affordances
  • Through changing states
  • Through analogy
  • Depth-first vs. Breadth-first
  • Path length and looping
  • Active involvement and testing

43
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

44
Experts and Chess Problems
Eye Movement Expert Novice
Gobet, F., http//www.psychology.nottingham.ac.uk/
credit/projects/chess_expertise/
45
Diagnosis 1
  • Understanding the situation
  • Diagnosing the salient features of a situation
  • Situation awareness past current predicted
    states
  • Estimating cues
  • Using intuitive statistics to estimate state of
    the world from samples
  • OK at estimating proportion within limits
    conservative bias at extremes
  • Estimates of variance skewed by extreme values
  • Not good at extrapolating nonlinear trends (tend
    to assume linearity)

46
Diagnosis 2
  • Cue seeking and hypothesis formation

Hypothesis / Belief H1 H2
Diagnosticity H1 0-1 H2
Information value
Reliability 0-1
Salience
Cues
H1 H2 ground truth
Wickens and Hollands, 2000, Engineering
Psychology and Human Performance
47
Cue seeking and hypothesis formation
  • Salience
  • Judgement of how relevant the features of
    specific cues are to the decision
  • Reliability
  • Judgement of how much a specific cue should be
    believed
  • Diagnosticity
  • How much evidence (as a probability) a specific
    cue provides for a given hypothesis

48
Integrating Cues
  • Missing Cues
  • Seek additional information
  • Fill in the gaps
  • Information Overload
  • Selective attention
  • More information leads to greater confidence (but
    not more accurate decisions)
  • Differential Salience
  • Conspicuous cues over processed, e.g., workload
  • Difficult cues not always used, e.g., pictures
    vs. numbers
  • No Differential Weighting of Cues
  • People treat all cues as if they have the same
    diagnosticity

49
Recognition-Primed Decision-Making
  • Account of Expert Decision-Making
  • e.g., in medicine, emergency services, military
  • Recognise situation, from previous experience,
    and apply known actions
  • Situation can be defined in terms of core
    features, and actions selected
  • Situation unfamiliar and decision-making explores
    alternative strategies prior to selection of
    action

50
Recognition-primed Decision-making
51
Heuristics and Biases 1
  • Representativeness
  • People use experience to decide which hypothesis
    is most likely to match the cues
  • Availability
  • People select the hypothesis that is most easy to
    imagine
  • Anchoring
  • People revise choices in terms of the initial
    hypothesis
  • Overconfidence bias
  • Less evidence is sought when people are confident
    of their hypothesis (regardless of whether it is
    correct)
  • Confirmation bias
  • People seek information to confirm their
    hypothesis (rather than counter evidence)

52
Heuristics and Biases 2
  • Framing Effect
  • The presentation of the problem can influence the
    decision
  • Healthy option 75 fat free
  • Unhealthy option 25 fat
  • Estimating probability
  • What are the odds of winning the Lottery?

53
Medical Diagnosis and History taking
  • Clinicians generate one or more working
    hypotheses early in the history-taking process
    when relatively few facts known about the
    patient.
  • Hypothesis activation dominates the early part of
    the diagnostic session as the physicians search
    for a context in which to proceed.
  • When a hypothesis activated, the physician uses
    this context--that is, his concept of a disease,
    a state, or a complication - as a model with
    which to evaluate new data from the patient
  • Such a model provides a basis for expectation it
    identifies the relevant clinical features that
    should prove fruitful for farther investigation. 
  • Hypotheses serve as organizing rubrics in working
    memory. They help to overcome limitations of
    memory capacity and serve to narrow the size of
    the problem space that must be searched for
    solution.

Kassirer, J. P., and Gorry, G. A., 1978, Clinical
Problem Solving A Behavioral Analysis, Ann. Int.
Med. 89, 247-248
54
Session Three Knowledge in the head versus
knowledge in the world
55
Working Assumptions
  • There are two approaches by which people interact
    with technology
  • The technology is treated as a problem to be
    solved
  • The technology is used with well-learned
    procedures
  • In both approaches, there is a need to match
    knowledge in the head with knowledge in the
    world

56
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

57
Open the file abc.txt in current directory
  • gt emacs /auto/abc.txt

58
Remembering UNIX commands
  • Kraut et al. (1983) 20 of 400 commands accouted
    for some 70 of usage
  • Draper (1985) expert UNIX users better than
    novices at discovering information

59
Find file abc.txt.
find / -name abc.txt -type f -print
60
Knowledge in the Worldexternal representations
and cognitive artefacts
61
Mapping
  • Naturalness
  • Related to directness of mapping
  • Related to expertise / familiarity
  • Appropriateness
  • Information should be appropriate to the task
    (neither more nor less)

62
Compatibility (see 1H1 notes)
  • Direction of motion stereotypes
  • Affordance
  • S-R compatibility
  • S-C-R compatibility

63
Artefacts Representation
  • Surface representation
  • Display and maintenance of symbols on a visible
    surface
  • Internal representation
  • Storage and organisation of symbols
  • External representation

64
Using an Abacus for Addition
Heaven beads 5 each
  • 6 2 8

Earth beads 1 each
8 2 10
65
Things that make us smart
  • Cognitive Artefacts used to assist everyday
    activity
  • Shopping List
  • Knotted handkerchief
  • Calculator
  • Diary

66
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

67
Shopping Lists
  • Memory aid
  • Do we only buy whats 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?

68
Cognitive Artefacts
  • Distribute actions across time
  • Pre-computation
  • Distribute actions across actors
  • Distributed cognition
  • Change actions required

69
What Question was this developed to answer?
  • Where am I?the portable timepiece was developed
    to help calculate longitude

Buxton, B., 2006, Less is more (more or less), in
The Invisible Future
70
Calculating Ships Speed
  • DRT, (RD/T) using pencil and paper
  • DRT, using calculator
  • 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

71
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

72
Calculating Noise Exposure
Nomogram versus Calculation
  • LEP,d log ftot. 90

dB(A)
0.1
f t antilog 0.1 (L 90)
8
73
Knowledge in the Headnotions of internal
representation
74
Some mental maths
  • Think of a number between 1 and 9
  • Subtract 5 from this number
  • Multiply the difference by 3
  • Square the product
  • Add the digits of this number
  • If the new number is lt5 then add 5, if the new
    number gt 5 then subtract 4
  • Multiply the difference by 2
  • Subtract 6 from the result

75
change the numbers to words
  • Think of the letter of the alphabet that
    corresponds to this number (A1, B2)
  • Think of a country starting with that letter
  • Think of the second letter of the country
  • Think of an animal that starts with this letter
  • Think of the animals colour
  • Think of a fruit that starts with the first
    letter of the colour
  • You now have in mind a country, an animal, a fruit

76
and you thought of.
Denmark Elephant Grape
77
Semantic Networks
Has Skin Can move Eats Breathes
ANIMAL
Can fly Has Wings Has feathers
BIRD
Has fins Can swim Has gills
FISH
Is Yellow Can sing
CANARY
Collins Quillian, 1969
78
Levels and Reaction time
A canary can sing
A canary can fly
A canary has gills
A canary has skin
Collins Quillian, 1969
A canary is a canary
A canary is a bird
A canary is a fish
A canary is an animal
79
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

80
Criticism of Collins and Quillians Model
  • Typicality Effect
  • People verify statements faster if they are about
    typical category members, e.g., A canary is a
    bird is verified faster than An ostrich is a
    bird
  • Search not proportional to Hierarchical Structure
  • Verifying A pig is an animal can be faster than
    A pig is a mammal even though it is higher
    up the hierarchy
  • Verifying A canary has wings might not involve
    moving to the bird node but have the
    information at the canary node.

81
Collins and Loftus Revision
  • Structure not hierarchical but spatial with
    short links between closely related concepts and
    with spacing related to experience

Sunset
Orange
Clouds
Red
Sunrise
Yellow
Green
Roses
Flowers
82
Connectionist Networks
  • Neural Circuits
  • Excitation and Inhibition
  • Strength of Firing
  • Graceful degradation

83
Schematic of Rumelhart and Normans connectionist
model of typing
middle ring index little
thumb Left hand
middle index ring thumb
little Right hand
Response system
Keypress node, breaking Word into typed
letters Excites and inhibits nodes
z
z
j
a
activation
Word node, activated from Visual or auditory
stimulus
jazz
84
  • Exercise 5
  • Define a chair

85
Concepts
  • How do you know a chair is a chair?

A chair has four legsdoes it? A chair has a
seatdoes it?
86
  • Exercise 6
  • On a scale of 1 (typical) to 7 (atypical), rate
    the following as examples of the concept
    FURNITURE
  • Chair Curtains
  • Sewing Machine Desk
  • Sofa Table
  • Telephone Vase
  • Dresser Fan
  • Clock Cooker

87
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

88
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

89
CD Player
5-6 3-4 0-2
90
Propositional Network
91
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

92
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

93
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

94
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

95
Mental Models
  • Partial
  • Procedures, Functions or System?
  • Memory or Reconstruction?

96
Yellow
97
Blue
98
Red
99
Green
100
Blue
101
Yellow
102
Green
103
Session FourAttention
104
Stroop Task
  • name the colours in which these words are printed
    as quickly as possible

Stroop, 1935
105
Conclusion
  • Reading words vs Naming colours
  • INTERFERENCE

106
Automatic vs Controlled
  • Automatic Processes are highly autonomous
  • Controlled Processes require conscious effort,
    i.e., need us to pay attention

107
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

108
Iconic MemoryAverbach Sperling (1960)
B F H K D C J M T R P N
109
Iconic Memory
B F H K D C J M T R P N
110
Iconic MemoryAverbach Sperling (1960)
  • 100 when cued to report a specific line (partial
    report) and when minimal cue delay
  • Decrement in recall with increasing cue delay
  • Whole report typically 4 out 12 (33)

111
Defining the icon
  • Pre-categorical trace
  • Literal copy of the visual stimulus
  • Very little perceptual treatment
  • Partial recall affected by spatial not
    categorical content, e.g., report specific line
    vs. recall letters
  • Visual trace
  • Factors limited to characteristics of the visual
    stimulus, e.g., intensity, duration, contrast.

112
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

113
Early SelectionBroadbent (1958)
114
Problems with Early Selection
  • Gray and Wedderburn (1960)
  • Left ear Right ear
  • 6 AUNT 3 DEAR 8 JANE
  • Should report Left ear then Right ear, but
    participants reported Words then Numbers

115
AttenuationTreisman (1964)
  • People do not ignore unattended channel
  • All information undergoes superficial semantic
    analysis to determine relevance
  • If information not relevant, then processing
    attenuated

116
Models of Selection
Short term memory
Perceptual process
Selective filter
Sensory register
Broadbent Triesman Deutsch and Deutsch
Sensory register
Attenuation control
Short term memory
Perceptual process
Selective filter
Sensory register
Perceptual process
Short term memory
117
Unattended Channel?
  • Broadbent(1958) 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

118
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

119
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 gt visual short term store

120
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

121
Allport et al. (1972)
  • Participants presented with essay, either visual
    and auditory
  • Recognition test far worse with auditory

Errors in Recognition ()
122
Brooks (1968)
F
  • Imagine F with moving around edge
  • When reaches junction or end, indicate Y (end)
    or N (junction)
  • Verbal say Yes or No
  • Tapping tap once for Y and twice for N
  • Pointing point to next Y or N in list
  • V T lt P
  • Indicating selective interference

123
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

124
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

125
Flexible Central Resource CapacityKahneman, 1973
126
Kahneman (1973)
  • Central pool of resources
  • Available resource depends on
  • State of the individual
  • Demands of the tasks
  • Aspects of the situation
  • Allocation of resources
  • Selective Attention
  • Strategic allocation
  • Momentary intentions
  • Enduring dispositions
  • Novelty
  • Meaningfulness
  • Parallel allocation to tasks

127
Multiple Resource Theory (Wickens, 1980)
128
Predictions and Evidence
  • Dual-task Experiments
  • Visual task (driving) better when Route Guidance
    presented using auditory rather than visual
    display (Parkes and Coleman, 1990)
  • Tracking tasks better time-shared with vocal
    response than manual response (Wickens et al.,
    1983)

129
Driving and Cell-phone use
  • Brookhuis et al., 1991, Accident Analysis
    Prevention
  • Manual manipulation of phone, e.g., dialling a
    number, interferes with control of car
  • Strayer Johnston, 2001, Psychological Science
  • Phone conversation can significantly increase
    time to react to a stimulus and probability of
    missing the stimulus
  • Interference proportional to complexity of the
    driving task (easy vs. difficult course) AND
    complexity of speech production (shadowing vs.
    generation)

130
Confusion and Similarity
  • Cooperation
  • Proximity principle, e.g., parallel processing of
    adjacent displays
  • Similarity of response dynamics
  • Confusion
  • Similarity of material, e.g., two spelling tasks
  • Conflict
  • Competition of material, e.g., Stroop task

131
Action-Selection Views (Allport, 1987)
  • Attentional mechanisms evolved to meet
    requirements of goal-directed behaviour
  • Goal defines the selection of an action
  • Selection of action defines which information
    needs to be extracted from available stimuli
  • Competition arises because selection of the
    action limits attention (rather than availability
    of resources)

132
  • Tipper et al., 1992
  • Respond to cue using buttons with distractor
    lights above them
  • Red respond
  • Yellow ignore
  • Arrangement of response front-to-back or
    back-to-front
  • Interference related to placing the distractor
    between target and response

133
Automaticity
  • Norman and Shallice (1980)
  • Fully automatic processing controlled by SCHEMATA
  • Partially automatic processing controlled by
    either Contention Scheduling
  • Supervisory Attentional System (SAS)

134
Supervisory Attentional System Model
Supervisory Attentional System
Control schema
Trigger database
Perceptual System
Effector System
Contention scheduling
135
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

136
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.

137
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

138
Tracking
  • Control movement of X to keep it on the path

139
Simple Tracking Activity
  • Compensatory tracking
  • Closed loop
  • Sample output and compare with input
  • Correct difference (error)
  • Pursuit tracking
  • Open loop
  • Focus on input
  • Assume dynamics known and anticipated

140
Anticipation
  • Anticipation requires some model of the system
    being controlled
  • Understanding system dynamics (knowledge)
  • Tuning of performance (practice)
  • Information from the world (sampling)

141
Signal Detection Theory
  • Detecting signals against noise

142
Distribution of responses
No
Yes
noise
signal
Correct rejection
Hit
False alarm
Miss
? Criterion beta
143
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

144
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

145
POC
P
P
M
Cost
Cost
Task A
Task A
M
Task B
Task B
  • Resource limited
  • Data limited

146
Session FivePerception
147
Data-driven perception
  • Activation of neural structures of sensory
    system by pattern of stimulation from environment

148
Theory-driven perception
  • Perception driven by memories and expectations
    about incoming information.

149
KEYPOINT
  • PERCEPTION involves a set of active processes
    that impose
  • STRUCTURE,
  • STABILITY,
  • and MEANING
  • on the world

150
Visual Illusions
Old Woman or Young girl?
http//www.genesishci.com/illusions2.htm
151
Exercise 7
i. X on outside front corner ii. X on
inside back corner
x
152
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

153
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

154
Designed to confuse?
Push the start button
155
Designed to confuse?
the start button
156
Marrs 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

157
Primal Sketch Processes
158
2½D Sketch
  • Figure-ground segregation
  • Determine foreground and background
  • Depth perception
  • Monocular
  • Linear perspective
  • Texture gradients
  • Binocular
  • Motion parallax
  • Correspondence and Convergence

159
Contrast Effects
This 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
160
Pandemoniuma model of featureextractionLinds
ay and Norman, 1977
161
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

162
2. Fundamentals of Graphical User Interface Design
  • Utility
  • Organisation of parts
  • Clutter on displays

163
Design can Influence Thinking
John Snow, 1854m Mapping death from cholera, in
London, showed clusters around water pump (and
not near brewery)
164
Attributes affecting utility
Legibility Font design Contrast Illumination Lumin
ance
Conspicuity Graphic design Spatial
coding Temporal coding Shape coding Colour coding
Readability Words Syntax
Display
Mediating User attributes
Psychological process Extraction of
meaning Comprehension
165
Gestalt Principles
166
Density and Clutter
  • Density is related to available screen space
  • E.g 80 x 24 line display 1920 character spaces
  • The proportion of filled spaces Density
  • Density averages 25 but rarely exceeds 50

167
Levels of Density
70 density 50 density 30
density
Shneiderman, 1992
168
Reducing Density
Grouping / tabulating Reduce number of words
Reduce number of characters
169
Conclusions
  • Understanding basic Gestalt principles helps
    manage focus
  • Some objects on a display are more conspicuous
    than others
  • Use highlighting sparingly
  • Some objects form perceptual groups
  • Use this to help design screen layout and to
    minimise risk of confusion

170
Eye-Movement Heat Maps
171
Reading
  • Saccades and Fixations
  • Anticipation and Inferences
  • Interpretation

172
Saccades and Fixations
173
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

174
Buffers Times for Reading
  • ms
  • 0 100 200 300 400
  • Photoreceptor stimulation
  • Iconic memory
  • Conceptual buffer
  • Articulatory loop
  • Visual spatial scratch pad
  • Central executive
  • Articulation

From Kintsch, W., 1998, Comprehension
175
Model of reading activity
Visual stimulus
Visual Analysis
Vpres
Grapheme-phoneme Correspondence rules
Mental lexicon
Apres
176
Interpretation
  • Knowledge of what you are looking at can aid
    in interpretation
  • JA CKAN DJI
  • LLW ENTU PTH
  • EHI LLT OFE
  • TCH APA ILO
  • FWA TER
  • Organisation of information is also useful

Gestalt also influences interpretation
177
Interpretation
  • Knowledge of what you are looking at can aid
    in interpretation
  • JA CKAN DJI
  • LLW ENTU PTH
  • EHI LLT OFE
  • TCH APA ILO
  • FWA TER
  • Organisation of information is also useful

178
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.

179
Story Grammar
Story
Episode
Setting
1
Reaction
Event
Internal response
Overt response
Event
Event
6
Event
Event
Event
Event
sadness
4
3
2
Change Of state
5
180
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 coming
  • 2. She remembered her pocket money
  • 3. She rushed into the house.

181
Inference and Recall
  • Thorndyke (1976) recall of sentences from Mary
    story
  • 85 correct sentence
  • 58 correct inference
  • sentence not presented
  • 6 incorrect inference

182
Session FiveMemory
183
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 cant remember something and
    then suddenly remember it much later?

184
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

185
Recall
  • Generate possible items, decide appropriateness
  • Direct match between information available and
    long-term memory

186
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

187
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)

188
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 lt Cued recall lt Recognition

189
Long Term Memory
  • Procedural
  • Knowing how
  • Declarative
  • Knowing that
  • Episodic vs. Semantic
  • Personal events
  • Language and knowledge of world

190
Production Systems
  • Knowing how to do X
  • Production rule set of conditions and an action
  • IF it is raining
  • And you wish to go out
  • THEN pick up your umbrella

191
Declarative memory
  • Knowledge for facts
  • How is this knowledge organised?

192
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

193
ACT
Declarative memory
Procedural memory
Retrieval Storage Match Execution
Working memory
Encoding Performance
OUTSIDE WORLD
194
Retrieval from LTM
  • Forgetting
  • Recall vs. Recognition

195
Forgetting
  • Encoding failure
  • Failure of consolidation
  • Storage failure
  • Disruption by new or existing information
  • Associative interference
  • Two responses associated with same stimulus
  • Retrieval failure

196
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

197
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
  • Ribots law person aged 60 can remember
    childhood events and early adult life, but
    increasingly vague for later life

198
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

199
Exercise 3
200
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.

201
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.

202
Exercise 3.3
  • This time you will hear a list of 20 words and
    you will tap two fingers of your right hand onto
    your left palm in a waltz rhythm during the
    presentation of the words.

203
Results for Exercises Last Week
204
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

205
Baddeleys (1986) Model of Working Memory
Central executive
Visual Cache
Inner scribe
Phonological store
Auditory word presentation
Visual word presentation
Articulatory control process
206
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

207
Cowan (1999) Embedded Processes Model of Working
Memory
208
Schematic of Cowans (1995)embedded processes
model
Central Executive
Long-term store
Controlled action
Automatic action
Activated memory
Brief sensory store
209
Cowans (1995) model
  • Working memory mechanism for activation of
    relevant long-term memory and for directing
    attention

210
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

211
Session Four Skill Expertise
212
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

213
Classification of skills Holding (1989)
Complex
ATC violin sleight-of-hand
DECISION
TRACKING
football piloting sailing draughting ballet
Closed (Motor, Habitual, Automatic)
Open (Perceptual, Controlled, Skilled)
TAPPING
VIGILANCE
detection sorting shot-putting
Simple
214
Reaction Time
  • Time to respond to a stimulus
  • Speed-accuracy trade-off
  • Proficiency requires response on time

215
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

216
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

217
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

218
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

219
Feedback
  • Prior to action
  • Anticipation / prompts
  • During action
  • Intrinsic
  • Kinaesthetic
  • Proprioception
  • Extrinsic
  • Post action
  • Knowledge of results

220
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

221
Salthouse (1986)
  • Input
  • Text converted to chunks
  • Parsing
  • Chunks decomposed to strings
  • Translation
  • Strings into characters and linked to movements
  • Execution
  • Key pressed

222
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

223
Schematic of Rumelhart and Normans connectionist
model of typing
middle ring index little
thumb Left hand
middle index ring thumb
little Right hand
Response system
Keypress node, breaking Word into typed
letters Excites and inhibits nodes
z
z
j
a
activation
Word node, activated from Visual or auditory
stimulus
jazz
224
Conclusions
225
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.

226
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

227
Key point 3
  • PERCEPTION involves a set of active processes
    that impose
  • STRUCTURE,
  • STABILITY,
  • and MEANING
  • on the world

Slide 228
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