Human Abilities

1
Human Abilities

• Sensory, motor, and cognitive capabilities

2
Outline

• Human capabilities
• Senses
• Motor systems
• Information processing
• Memory
• Cognitive Processes
• Selective attention, learning, problem solving,
  language
• Predictive Models -gt next lecture

3
Typical Person

• Do we really have limited memory capacity?

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Basic Human Capabilities

• Do not change very rapidly
• Not like Moores law!
• Have limits, which are important to understand
• Our abilities to not change, but our
  understanding of them does
• Why do we care?
• Better design!
• Want to improve user performance
• Universal design design for everyone, including
  those with disabilities
• Well come back to this later in the semester

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Usable Senses

• The 5 senses (sight, sound, touch, taste and
  smell) are used by us every day
• 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

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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

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Vision implications (more to come in visual
design)

• Color
• Distinguishable hues, optical illusions
• About 9 of males are red-green colorblind!
• See http//colorlab.wickline.org/colorblind/colorl
  ab/
• Acuity
• Determines smallest size we can see
• Less for blue and yellow than for red and green

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Color/Intensity Discrimination

• The 9 hues most people can identify are
• Color Wavelength
• Red 629
• Red-Orange 596
• Yellow-Orange 582
• Green-Yellow 571
• Yellow-Green 538
• Green 510
• Blue-Green 491
• Blue 481
• Violet-Blue 460

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Color Surround Effect

• Our perception of a color is affected by the
  surrounding color

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Effect of Colored Text on Colored Background
Black text on white Gray text on white Yellow
text on white Light yellow text on white Green
text on white Light green text on white Blue text
on white Pale blue text on white Dark red text on
white Red text on white Rose text on white
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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 ?

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Touch

• Three main sensations handled by different types
  of receptors
• Pressure (normal)
• Intense pressure (heat/pain)
• Temperature (hot/cold)
• Where important?
• Mouse, Other I/O, VR, surgery

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Motor System (Our Output 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

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Work Station Ergonomics to Facilitate I/O
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The Mind

• And now on to memory and cognition

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The Model Human Processor

• A true classic - see Card, Moran and Newell, The
  Psychology of Human-Computer Interaction,
  Erlbaum, 1983
• 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)
• Neglects effect of other people

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Memory

• Perceptual buffers
• Brief impressions
• Short-term (working) memory
• Conscious thought, calculations
• Long-term memory
• Permanent, remember everything that ever happened
  to us

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LONG-TERM MEMORY
R Semantic D Infinite S Infinite
SHORT-TERM (WORKING) MEMORY
AUDITORY IMAGE STORE
VISUAL IMAGE STORE
R Acoustic or Visual D (one chunk) 73 73-226
s D (3 chunks) 7 5-34 s S 7 5-9 chunks
R Acoustic D 1.5 0.9-3.5 s S 5 4.4-6.2
letters
R Visual D 200 70-1000 ms S 17 7-17
letters
PERCEPTUAL PROCESSOR C 100 5-200 ms
COGNITIVE PROCESSOR C 70 27-170 ms
MOTOR PROCESSOR C 70 30-100 MS
R Representation D Decay Time S Size C
Cycle Time
Eye movement (Saccade) 230 70-700 ms
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Sensory Stores

• Very brief, but accurate representation
• Physically encoded
• Limited capacity
• Iconic 7-17 letters
• Echoic 4-6
• Haptic ??
• Rapid Decay
• Iconic 70-1000 ms
• Echoic 0.9 3.5 sec
• Attention filters information into short term
  memory and beyond for more processing
• Perceptual Processor interpret signal into
  semantically meaningful
• Pattern recognition, language, etc.

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Short Term Memory

• Symbolic, nonphysical acoustic or visual coding
• Somewhat limited capacity
• 7 - 2 chunks of information
• Slower decay
• 5-226 sec
• rehearsal prevents decay
• Another task prevents rehearsal - interference

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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
• User and task dependent

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Implications?

• Which is an implication of 7 - 2?
• Use 5-9 items on a menu
• Display 5-9 icons on a task bar
• No more than 7 tabs on a window
• 5-9 items in a list

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Long-Term Memory

• Semantic storage
• Seemingly permanent unlimited
• Access is harder, slower
• -gt Activity helps (we have a cache)
• Retrieval depends on network of associations
• How information is perceived, understood and
  encoded determines likelihood of retrieval

File system full
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LT Memory Structure

• Episodic memory
• Events experiences in serial form
• Helps us recall what occurred
• Semantic memory
• Structured record of facts, concepts skills
• One theory says its like a network
• Another uses frames scripts (like record
  structs)

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Memory Characteristics

• Things move from STM to LTM by rehearsal
  practice and by use in context
• 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

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Recognition over Recall

• We recognize information easier than we can
  recall information
• Examples?
• Implications?

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Processes

• Four main processes of cognitive system
• Selective Attention
• Learning
• Problem Solving
• Language

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Selective Attention

• We can focus on one particular thing
• Cocktail party chit-chat
• Salient visual cues can facilitate selective
  attention
• Examples?

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Learning

• Two types
• Procedural How to do something
• Declarative Facts about something
• Involves
• Understanding concepts rules
• Memorization
• Acquiring motor skills
• Automotization
• Tennis
• Driving to work
• Even when dont want to
• Swimming, Bike riding, Typing, Writing

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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
• gt Consider users previous knowledge in your
  interface design

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Observations

• Users focus on getting job done, not learning to
  effectively use system
• Users apply analogy even when it doesnt apply
• Or extend it too far - which is a design problem
• Dragging floppy disk icon to Macs trash can does
  NOT erase the disk, it ejects disk!

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Problem Solving

• Storage in LTM, then application
• Reasoning
• Deductive If A then B
• Inductive - Generalizing from previouscases to
  learn about new ones
• Abductive - Reasons from a fact to theaction or
  state that caused it
• Goal in UI design - facilitate problem solving!
• How??

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Observations

• We are more heuristic than algorithmic
• We try a few quick shots rather than plan
• Resources simply not available
• We often choose suboptimal strategies for low
  priority problems
• We learn better strategies with practice

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Implications

• Allow flexible shortcuts
• Forcing plans will bore user
• Have active rather than passive help
• Recognize waste

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Language

• Rule-based
• How do you make plurals?
• Productive
• We make up sentences
• Key-word and positional
• Patterns
• Should systems have natural language interfaces?
• Stay tuned

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Recap
II. Information processing A. Perceptual B.
Cognitive 1. Memory a. Short
term b. Long term 2. Processes
a. Selective attention b.
Learning c. Problem solving
d. Language
I. Senses A. Sight B. Sound C. Touch
D. Smell
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People

• Bad
• aaa
• bbb
• ccc

• Good
• xxx
• yyy
• zzz

Fill in the columns - what are people good at and
what are people bad at?
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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

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Class DiscussionModel Human Processor

• How good is the model?
• What kinds of assumptions are they making?

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Assignment Scenarios

• Make sure it is a story with
• Actors (at least one person)
• Actions (not just the context)
• Good focus on the negative
• Try to follow through with what the person does

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Next Assignment HTA

• Current activity that relates to your project
  topic
• Either create diagram and upload the file to the
  Swiki
• Or use the numbered outline approach
• Dont forget those plans!