Human Abilities Part 1 of 3

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Human Abilities - Part 1 of 3

• Understanding the user Introduction, the
  Senses, the Motor System

This material has been developed by Georgia Tech
HCI faculty, and continues to evolve.
Contributors include Gregory Abowd, Jim Foley,
Diane Gromala, Elizabeth Mynatt, Jeff Pierce,
Colin Potts, Chris Shaw, John Stasko, and Bruce
Walker. Comments directed to foley_at_cc.gatech.edu
are encouraged. Permission is granted to use with
acknowledgement for non-profit purposes. Last
revision January 2004.
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Outline

• Human capabilities
• Senses
• Motor systems
• Information processing
• Memory
• Cognitive Processes
• Selective attention, learning, problem solving,
  language
• Simple predictive models

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Typical Person )

• Do we really have limited memory capacity?
• Stay tuned

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Basic Human Capabilities

• Do not change very rapidly
• Not like Moores law!
• Have limits, which are important to understand
• Our understanding of human capabilities does
  change, ie
• Cognitive neuroscience
• Theories of color perception
• Effect of groups and situation on how we act and
  react

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Human Capabilities

• Why do we care?
• Better design!
• Want to improve user performance
• Knowing the user informs the design
• Senses
• Information processing systems
• Physical responding

Time and effort expendedto complete tasks
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Overview
I. Senses A. Vision B. Hearing C. Touch
D. Smell
III. Motor system A. Hand movement B.
Workstation Layout
II. Information processing A. Perceptual B.
Cognitive 1. Memory a. Short
term b. Medium term c. Long
term 2. Processes a. Selective
attention b. Learning c.
Problem solving d. Language
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Senses (Our Input System)

• Sight, hearing, touch important for current HCI
• Smell, taste ???
• Abilities and limitations affect design

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Key concepts for Senses

• Just noticeable difference (jnd)
• How much of a change in stimulus is needed before
  can be sensed
• Tends to be logarithmic - Webers Law
• Magnitude of physical stimulus versus perceived
  magnitude
• (Doubling number of photons does not double
  perceived intensity)

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Vision (Covered in greater detail in section on
visual design)

• Visual System
• Eye
• Retina
• Neural pathway
• 80 of brains operation

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Color JND
JND, mm
Color, from 400 to 700 mm V I B G Y
O R
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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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Auditory JND

• Pitch
• Loudness
• Location
• Temporal variation (eg, songs) is another
  dimension

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Touch

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

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Touch JND

• Spatial - relevant for reading braille
• Pressure
• Temperature

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Smell

• Joseph Kaye, Making scents aromatic output for
  HCI ACM interactions Volume 10, Number 1 (2004),
  Pages 48-61

Solenoid-controlled scent bottles
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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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End Part 1