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AVI/Psych 358/IE 340: Human
Factors
Cognition
September 12-17 2008
Admin
• HW 1 (Due next Friday)
• Re-organized groups (check your groups)
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Overview
• What is cognition?
• What are users good and bad at?
• Describe how cognition has been applied to
interaction design
• Theories of cognition
– Mental models
– Theory of action, evaluation (action cycle)
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Cognition: What goes on in the
mind?
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Why do we need to understand users?
• Interaction requires cognition
– Need to understand cognitive abilities and limitations of users
– Provide support in situations of cognitive limitations
• Develop better interactive products by understanding
cognitive processes of users
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Core cognitive aspects
• Attention
• Perception and recognition
• Memory
• Reading, speaking and listening
• Problem-solving, planning, reasoning and decision-making, learning
• Most relevant to interaction design are attention, perception and
recognition, and memory
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Attention
• Selecting things to concentrate on at a point
in time from the mass of stimuli around us
• Allows us to focus on information that is
relevant to what we are doing
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Attention
• Could involve audio and/or visual senses
• Examples of interface components to support
human attention: color, boundaries, flashing,
grouping (e.g. drop down menus)
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Activity: Find the price of a double room at the Holiday
Inn in Bradley
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Activity: Find the price for a double room at the Quality
Inn in Columbia
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What catches your eye?
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London Underground RR
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Design guidelines for attention
• Make information salient when it needs attending to
• Use techniques that make things stand out like color, ordering,
spacing, underlining, sequencing and animation
• Avoid cluttering the interface - follow the google.com example of
crisp, simple design
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What attention design guidelines
are implemented on Google?
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Perception and recognition
• How information is acquired from the world via the
different sense organs (vision, sound, touch etc)
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Perception and recognition
• Obvious implication is to design representations that are
readily perceivable, e.g.
– Structuring information
– Text should be legible
– Icons should be easy to distinguish and understand
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Which is easiest to read and
why?
What is the time?
What is the time?
What is the time?
What is the time?
What is the time?
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flom
vask
dute
geng
cruke
stoff
lonnup meby
froo
nite
heem aremp racan
tane
niddo
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yellow purple
blue
red
green
purple green
red
blue
purple
brown
blue
orange
red
green
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Design Guidelines
• Representations of information need to be designed to
be perceptible and recognizable
– E.g. clearly delineated boundaries, color etc
• Icons and graphical representations to enable users to
readily distinguish their meaning
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Design Guidelines
• Bordering and spacing to effectively group
information
• Use of sounds
• Text should be legible and distinguishable from
the background
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Perception
• Constructing meaning through perception
• Organizing visual sensory data
• Grouping units together (perception of
rows, columns, figures, relationships etc)
• Design goal: support the perceptual
process
– Layout and organization, avoid ambiguity
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Ambiguity in Perception
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Gestalt Principles
a
b
proximity
c
d
continuity
closure
similarity
symmetry
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Examples from UI
Proximity
Similarity
Closure
Symmetry
Continuity
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Examples from UI (Cont’d)
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Computer Vendor Activity
Analyze www.apple.com and www.dell.com with respect to their
perceptual aspects: (1) gestalt, (2) virtual affordances and (3)
other perceptual elements
Proximity
Similarity
Closure
Symmetry
Continuity
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Memory
• Involves first encoding and then retrieving
knowledge
• We don’t remember everything - involves filtering
and processing what is attended to
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Memory
• Context is important in affecting our memory (i.e.,
where, when)
• Well known fact that we recognize things much
better than being able to recall things
– Better at remembering images than words
– Why interfaces are largely visual
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Processing in memory
• Encoding is first stage of memory
– determines which information is attended to in the environment
and how it is interpreted
• Higher the attention paid to something, better the recall
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Processing in memory
• And the more it is processed in terms of thinking about it
and comparing it with other knowledge
• Repetition is another way of reinforcing memory (e.g.
repeated use of a software system)
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Miller’s theory
• George Miller’s theory of how much information people
can remember
• People’s immediate memory capacity is very limited
• Many designers have been led to believe that this is
useful finding
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Magic Number‘72’
• People can remember 7+/- 2 ‘chunks’ of
information
• For example: read a list of numbers and try to
repeat it without looking at them
• ‘Chunks’ – are logical combinations that can be
derived (e.g. related words – microwave oven;
referee-umpire)
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What some designers get up to…
•
•
•
•
•
Present only 7 options on a menu
Display only 7 icons on a tool bar
Have no more than 7 bullets in a list
Place only 7 items on a pull down menu
Place only 7 tabs on the top of a website page
– But this is wrong? Why?
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Why?
• Inappropriate application of the theory
• People can scan lists of bullets, tabs, menu items till they
see the one they want
• They don’t have to recall them from memory having only
briefly heard or seen them
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Recap
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Cognition
• Perception – forming consciousness
• Working memory – temporal storage
• Long-term memory – information retrieval
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Attention
• Attention Resources, a pool of attention
or mental effort
– Limited availability
– Can be allocated to processes as required
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Selective Attention-Salience
• Attentional capture
–
–
–
–
–
Captures attention automatically
Distinct color
Unique rhythm
Sudden vibration
Abrupt onset of a flash
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HF guidelines in Perception
• Maximize bottom-up processing
– Legibility, contrast, bigger fonts, etc.
• Maximize automaticity and unitization
– Familiar perceptual representations
• Maximize top-down processing
– Past experiences
– Associations, e.g. green for go, red for no-go
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Working memory
• Is limited
• 7±2
• Chunking
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HF guidelines in Working memory
•
•
•
•
Minimize working memory load
Exploit chunking
Minimize confusability
Consider working memory limits in
instructions
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Long term memory
• Storing information and retrieving it at
later times
• Semantic memory – facts or procedures
• Event memory – specific events
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Long term memory
• Frequency and recency of its use
– A password used everyday vs. occasionally
– A newly learned skill used the next day or 3
months later
• Association
– How one item may be linked with other items
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Long term memory - Forgetting
• Why do we forget things?
– Weak strength due to low frequency or
recency
– Weak associations
– Interfering associations
• Learning & Training
• Recall vs. recognition
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Long term memory – Implications for
design
• Increase frequency and recency
• Standardize controls, displays, symbols,
operating procedures, etc.
• Use memory aids
• Add meaningfulness
• Support mental model
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