Transcript Humans and Models - Personal Web Pages

Human Abilities and
Models
Sensory and cognitive abilities and
models, models of human performance
Outline
 Human capabilities and disabilities
 Senses
 Motor systems
 Memory
 Cognitive Processes
 Selective attention, learning, problem solving,
language
 Contextual models
Typical Person
 Do we really have limited memory capacity?
Basic Human Capabilities
 Do not change very rapidly
 Not like Moore’s law!
 Have limits, which are important to understand
 Why do we care?
 Better design!
 Want to improve user performance
 Universal design – designing for all people, including
those with disabilities
But… we’re all disabled
sometimes
 Environment
 Fatigue
 Injury
 Aging
 Changing role of information technology
Usable Senses
The 5 senses (sight, sound, touch, taste and smell) are used by us
every day
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each is important on its own
together, they provide a fuller interaction with the natural world
Computers rarely offer such a rich interaction
Can we use all the available senses?
 ideally, yes
 practically – no
We can use
• sight • sound • touch (sometimes)
We cannot (yet) use
• taste • smell
Vision Fundamentals
 Retina has
6.5 M cones (color
vision), mostly at fovea
(1/3)˚
 About 150,000 cones per
square millimeter
 Fewer blue sensing
cones than red and
green at fovea
 100 M rods (night vision),
spread over retina, none
at fovea
 Adaptation
 Switching between dark
and light causes fatigue

Vision implications (more to come in visual
design)
 Color
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Distinguishable hues
optical illusions
 Acuity
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Determines smallest size we can see
Less for blue and yellow than for red and
green
Color/Intensity Discrimination
 The 9 hues most people can identify are:
Color
Red
Red-O range
Yellow-O range
Green-Yellow
Yellow-Green
Green
Blue-Green
Blue
Violet-Blue
Wavelength
629
596
582
571
538
510
491
481
460
Color Surround Effect
 Our perception of a color is affected by the
surrounding color
Vision Difficulties
 Color blindness
About 9 % of males are red-green colorblind!
 See http://colorlab.wickline.org/colorblind/colorlab/
 Low-vision
 The vast majority of visually disabled people have
some sight
 Blindness
 Rely on other senses to receive information
 Specialized hardware and software
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Screen readers
Braille printers, etc.
Myopia and Hypermetropia
 Myopia
 (short-sighted)
Hypermetropia
(far-sighted)
Macular degeneration
Diabetic retinopathy
Cataracts
Tunnel vision
Accommodating Partial Sight
 Large monitor, high resolution, glare
protection
 Control of color and contrast
 Control of font size everywhere
 Keyboard orientation aids
Accommodating Blind Users
 Screen Readers
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Full-featured
Cursor-tracking, routing
Dialogue focus
View areas
 Auditory or tactile output
http://www.freedomscientific.com/fs_products/software_jaws.asp
http://www.webaim.org/simulations/screenreader
Audition (Hearing)
 Capabilities (best-case scenario)
 pitch - frequency (20 - 20,000 Hz)
 loudness - amplitude (30 - 100dB)
 location (5° source & stream separation)
 timbre - type of sound (lots of instruments)
 Often take for granted how good it is
(disk whirring)
 Implications ?
Hearing uses
 Redundant output

Email beep + icon, IM sound + popup
message, etc.
 Output when screen not available
 Multimedia systems
Hearing problems or deafness
 An increasing problem?
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Population
Phone interfaces
 Various technologies used:
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Communication aids
Automated software (speech to text, etc.)
Touch
 Three main sensations handled
by different types of receptors:
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Pressure (normal)
Intense pressure (heat/pain)
Temperature (hot/cold)
 Where important?
 Mouse, Other I/O, VR, surgery
Motor System
 Capabilities
 Range of movement, reach, speed,
strength, dexterity, accuracy
 Workstation design, device design
 Often cause of errors
 Wrong button
 Double-click vs. single click
 Principles
 Feedback is important
 Minimize eye movement
 See Handbooks for data
Work Station Ergonomics – to
Facilitate I/O
Large Range of Physical
Impairments
Complete lack of function
 absence of a limb
 paralysis – usually due to spinal injury, the
higher the damage the greater the degree of
paralysis
Lack of strength
Tremor/lack of accuracy
Slowness
Implications
 Try to minimize movement and strain
 Alternative input devices
 Keyboard hardware and software
 Speech input
 Other input switches for more severe needs
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Eye gaze, sip and puff, etc.
Acceleration techniques
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Word completion, macros, etc.
The Mind
 And now on to memory and cognition…
The “Model Human Processor”
 A true classic - see Card, Moran and Newell, The
Psychology of Human-Computer Interaction,
Erlbaum, 1983
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Microprocessor-human analogue using results from
experimental psychology
Provides a view of the human that fits much
experimental data
But is a partial model
 Focus is on a single user interacting with some entity
(computer, environment, tool)
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Neglects effect of other people
Memory
 Perceptual “buffers”
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Brief impressions
 Short-term (working) memory
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Conscious thought, calculations
 Long-term memory
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Permanent, remember everything that ever
happened to us
LONG-TERM MEMORY
R = Semantic
D = Infinite
S = Infinite
SHORT-TERM (WORKING) MEMORY
VISUAL IMAGE
STORE
R = Visual
D = 200 [70-1000] ms
S = 17 [7-17] letters
AUDITORY IMAGE
STORE
R = Acoustic
D = 1.5 [0.9-3.5] s
S = 5 [4.4-6.2] letters
R= Acoustic or Visual
D (one chunk) = 73 [73-226] s
D (3 chunks) = 7 [5-34] s
S = 7 [5-9] chunks
PERCEPTUAL
PROCESSOR
COGNITIVE
PROCESSOR
MOTOR
PROCESSOR
C = 100 [5-200] ms
C = 70 [27-170] ms
C = 70 [30-100] MS
R = Representation
D = Decay Time
S = Size
C = Cycle Time
Eye movement (Saccade) = 230 [70-700] ms
Sensory Stores
 Very brief, but accurate representation of what was
perceived
 Physically encoded
 Details decay quickly (70 - 1000 ms visual; 0.9 - 3.5 sec
auditory)
 Limited capacity
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Iconic – visual
 7 - 17 letters; 70 - 1000 ms decay
Echoic – auditory
 4 - 6 auditory; 0.9 - 3.5 sec auditory
Haptic - touch
 Attention filters information into short term memory and
beyond for more processing
Short Term Memory
 Symbolic, nonphysical acoustic or visual
coding
 Decay 5-226 sec, rehearsal prevents decay
 Another task prevents rehearsal –
interference
 Use “chunks”: 7 +- 2 units of information
About Chunks
 A chunk is a meaningful grouping of
information – allows assistance from LTM
 4793619049 vs. 704 687 8376
 NSAFBICIANASA vs. NSA FBI CIA NASA
 My chunk may not be your chunk
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User and task dependent
Long-Term Memory
 Seemingly permanent & unlimited
 Access is harder, slower
 -> Activity helps (we have a cache)
 Retrieval depends on network of associations
 How information is perceived, understood and
encoded determines likelihood of retrieval
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Effected by emotion, previous memory
File system full
LT Memory Structure
 Episodic memory
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Events & experiences in serial form
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Helps us recall what occurred
 Semantic memory
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Structured record of facts, concepts & skills
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Semantic network theory
Or theory of frames & scripts (like record structs)
Memory Characteristics
 Things move from STM to LTM by rehearsal &
practice and by use in context
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Do we ever lose memory? Or just lose the link?
What are effects of lack of use?
 We forget things due to decay and interference
 Similar gets in the way
Recognition over Recall
 We recognize information easier than we can
recall information
 Examples?
 Implications?
Processes
 Four main processes of cognitive system:
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Selective Attention
Learning
Problem Solving
Language
Selective Attention
 We can focus on one particular thing
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Cocktail party chit-chat
 Salient visual cues can facilitate selective
attention
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Examples?
Learning
 Two types:
 Procedural – How to do something
 Declarative – Facts about something
 Involves
 Understanding concepts & rules
 Memorization
 Acquiring motor skills
 Automatization
 Tennis
 Driving to work
 Even when don’t want to
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Swimming, Bike riding, Typing, Writing
Learning
 Facilitated
 By structure & organization
 By similar knowledge, as in consistency in UI design
 By analogy
 If presented in incremental units
 Repetition
 Hindered
 By previous knowledge
 Try moving from Mac to Windows
=> Consider user’s previous knowledge in your
interface design
Observations
 Users focus on getting job done, not learning
to effectively use system
 Users apply analogy even when it doesn’t
apply

Or extend it too far - which is a design problem
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Dragging floppy disk icon to Mac’s trash can does
NOT erase the disk, it ejects disk!
Problem Solving
 Storage in LTM, then application
 Reasoning
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Deductive - If A, then B
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Inductive - Generalizing from previous
cases to learn about new ones
 Abductive Reasons from a fact to the
action or state that caused it
 Goal in UI design - facilitate problem solving!
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How??
Observations
 We are more heuristic than algorithmic
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We try a few quick shots rather than plan
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Resources simply not available
 We often choose suboptimal strategies for
low priority problems
 We learn better strategies with practice
People
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Good
1.
2.
3.
xxx
yyy
zzz
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Bad
1.
2.
3.
aaa
bbb
ccc
Fill in the columns what are people good at
and what are people
bad at?
People
 Good
 Infinite capacity LTM
 LTM duration &
complexity
 High-learning capability
 Powerful attention
mechanism
 Powerful pattern
recognition
 Bad
 Limited capacity STM
 Limited duration STM
 Unreliable access to
LTM
 Error-prone processing
 Slow processing
Models
 Translating empirical evidence into theories and
models that influence design.
 Performance measures
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Quantitative
Time prediction
Working memory constraints
 Competence measures
 Focus on certain details, others obscured
 More on predictive models in March
Context and Cognition
 Human information processor models all
involve unaided individual
 In reality, people work with other people and
other artifacts
 Other models of human cognition
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Situation action
Activity theory
Distributed cognition
How theories get used
 Descriptive power – conceptual framework for
describing the world
 Rhetorical power – name important
conceptual structures we can relate to the
world
 Inferential power – help make inferences
(maybe about new change or design…)
 Application – informing and guiding system
design
Distributed Cognition (DCog)
 HCI Proponent: Ed Hutchins
 Distributed collection of interacting people
and artifacts, and the communication and
coordination between them
Distributed Cognition
 Cognitive System – the people, artifacts and
environments
 Communicative pathways – the information
channels
 Describes information flow in terms of
propagation across representational state
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Information is transformed through different
media (computers, displays, paper, heads)
What’s involved
 The distributed problem-solving that takes
place
 The role of verbal and non-verbal behavior
 The various coordinating mechanisms that
are used (e.g., rules, procedures)
 The communication that takes place as the
collaborative activity progresses
 How knowledge is shared and accessed
Activity Theory
 Long history from cognitive science
 HCI proponent: Bonnie Nardi
 Explains human behavior in terms of our practical
activity with the world
 Provides a framework that focuses analysis around
the concept of an ‘activity’ and helps to identify
tensions between the different elements of the
system
 Two key models: one outlines what constitutes an
‘activity’; one models the mediating role of artifacts
Activity Theory
 Unit of analysis is an activity
 Components:
subject, object, actions, operations
Noun
Held by subject, Goal-directed
motivates activity processes
“object of game” “tasks”
How action
is carried out
Individual model
A.T. Principles
 Key idea: Notion of mediation by artifacts
 Our work is a computer-mediated activity
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Starring role goes to activity
In “regular” HCI, stars are person and machine
 Context is not “out there”. It is generated by
people in activities
Example: call center
 DCog:
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Examine how information is transformed as it
goes from caller, to employee, into the system
for information, back to employee and then
caller…
 Activity Theory
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Examine tensions between parts of the system
such as community, tools, rules, etc.
Situated Action
 Noted proponent: Lucy Suchman
 Much of the theory that underlies
ethnography
 Structuring of an activity grows out of
immediacy of the situation
 People engage in opportunistic, flexible ways
to solve problems
Situated Action
 Studies situated activity or practice
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Activity grows out of the particulars of a
situation
Improvisation is important
 Basic unit of analysis is “the activity of
persons acting in a setting”
Example
 Need 3/4 of 2/3 of cup of cottage cheese
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Just has a simple measuring cup available
 Person solves problem by
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Measuring 2/3 cup
Pouring out into a circle
Divide into quadrants
Take away one
 One time solution to one time problem
Other comments on S.A.
 Emergent property of moment-by-moment
interactions
 Improvisation
 Detailed temporal accounts
 De-emphasizes rigid plans and rational
problem solving
Comparing Models
 The role of goals or intentions
 S.A.: “retrospective reconstructions”
 A.T. & D.C: central
 Persistent structures
 S.A.: emphasize emergent/ contingent/ improvisatory
over routine/predictable
 A.T.: our activity assimilates experience of humanity
 D.C.: much focus on transformation of artifacts over
time
Comparing Models
 People and things
 MHP: model each as a “machine”, study the
diad of H-C
 S.A.: qualitatively different, but mostly reactive
 A.T.: individual at center
 D.C.: both are agents, study multi-agent
system
Some Commentary
 Take the reading with a grain of salt.
 How does this influence design?