Transcript Slides for Lecture 14

Lecture 14:
Ergonomics and Human Factors
for Interaction Techniques
Brad Myers
(based on material by
Jeffrey M Rzeszotarski)
05-440/05-640:
Interaction Techniques
Spring, 2016
© 2016 - Brad Myers
Source: Maltron
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Human Factors &
Ergonomics
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Human factors is concerned with the
understanding of interactions among
humans and other elements of a system,
and the profession that applies theory,
principles, data and methods to design in
order to optimize human well-being and
overall system performance.
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Human Factors
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Investigations of disasters / accidents
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see Air Crash Investigation series for a demo of
this process, or this Therac 25 report
Understanding where errors may happen
Designing new products or systems
Physiological, cognitive, behavioral, social,
organizational, cultural, etc.
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Human Factors
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Time and Motion Studies
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Time and Motion Studies
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Taylor, Gilbreth, Ford
Improve worker performance through
scientific practice – Scientific Management
Observe experts, figure out why they
perform well, make others like them
Worker rights
Injury and other human factors
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Time and Motion Studies
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Time-Motion Study: "The Easier Way" 1946
General Motors Corporation, Employee
Cooperation Staff (12:31)
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https://www.youtube.com/watch?v=k9vIhPszb2I
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(pardon the dated, 40s depictions of gender,
home, and society)
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Anthropometry
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Measure populations to understand human
body’s structure
Drive design to incorporate measurement
and compatibility with variety of bodies
Is there such a thing as an ‘average’ person
in a population?
Airplane seats vs. changing populations
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Anthropometry
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Anthropometry
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Physical Factors
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“Ergonomics”
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Work-related injuries
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Musculoskeletal injuries
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OSHA
Repetitive strain injuries (RSI)
Vibration injuries
Fractures, sprains, and breaks
Vision, hearing, or cognitive impairment
Accidents
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Computer
Posture
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Seating position
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Erect posture
Back supported
Feet flat on ground
Eyes forward
90 degree elbow
Wrist straightened
Adjustable chair
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RSI
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Repetitive strain injuries
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Repetition of many
physical actions over time,
performed in an unsafe manner
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Muscles in tension or nerves compressed
No sudden onset – may take 5 years
Permanent, irreversible damage
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Pointing Device Injuries
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Pointing Device Injuries
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“Gorilla-arm” Syndrome
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Text Entry Injuries
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“Blackberry thumb” RSI
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Research: Attempt to
reduce RSI for text entry
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Jen Mankoff, Greg Abowd, “Cirrin: a word-level unistroke
keyboard for pen input”, UIST’98.
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No need to lift stylus
from surface
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Other Physical Issues
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Displays
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Eye focus problems
Lighting vs. screen – flicker and flashing
Brightness & sleep
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Cognitive (Mental) / Behavioral
Factors
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Human Decision Making
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Delayed gratification
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Bias towards immediate gains
Framing - cost vs. gain
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Losses ‘worse’ than equal gains
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Eye Movements
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Eye does not make smooth movements
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Saccades – jumps from region to region
Area of attention is not necessarily the precise
center of eye focus
Often a top-down process
Eye Tracking studies
Why might eye tracking
be hard to use as a pointing
device?
What about scrolling using
eye tracking?
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“Midas problem”
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Perception
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Stimuli are encoded in their simplest form
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Memory
Working Memory
Procedural Memory
Declarative Memory
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Working Memory
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4-7 units of information
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Chunking – we ‘package’ information rather
than store as-is
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Working Memory
N C I U F B S R S IASAIA
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Working Memory
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Working Memory
C IA N SA I R S F B I U SA
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Working Memory
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Working Memory
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Did you store those differently?
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Experts chunk information differently
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Chess masters can look more moves ahead
because they store more efficiently
Memory experts use advanced chunking
techniques to memorize hundreds of digits
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Working Memory
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You can help users chunk information in
interfaces
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(412) 286-2000
Menu hierarchies
Other examples?
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Procedural Memory
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How to accomplish a task
Subconscious
Experienced driving, touch-typing, using
keyboard accelerators
Acquired during expertise development
Process called “automatization”
Automatized tasks don’t require much attention
to perform
Can interfere if tasks are similar
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Switching from QWERTY to Dvorak
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Interference
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Attention
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Finite pool of attention resources
Multitasking divides the pool
Overload –
Insufficient
resources
cause
mistakes or
poor
performance
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