1. Cognitive Aspects (Review) Usability Principles
IAT 334 Interface Design
Cognitive Aspects (Review)
Usability Principles
______________________________________________________________________________________ SCHOOL OF INTERACTIVE ARTS + TECHNOLOGY [SIAT] |
Jan 20, 2011
IAT 334

2. Agenda Cognitive Processes Usability Principles Implications
Motor system
Usability Principles
Learnability Principles
Flexibility Principles
Robustness Principles
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3. Basic HCI Model Human Processor Components:
A simple model of human cognition
Card, Moran, Newell 1983
Components:
Senses
Sensory store
Short-term memory
Long-term memory
Cognition
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4. Model Human Processor Basics
Based on Empirical Data
Three interacting subsystems
Perceptual (read-scan)
Cognitive (think)
Motor (respond)
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5. Information Processing
Usually serial action
Respond to buzzer by pressing button
Usually parallel recognition
Driving, reading signs, listening to radio
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6. Processes Four main processes of cognitive system: Selective Attention
Learning
Problem Solving
Language
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7. Selective Attention We can focus on one particular thing
Eg cocktail party talk
Salient visual cues can facilitate s.a.
Examples?
Bold, Larger fonts
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8. Learning Procedural Learning: Declarative Learning: Involves
How to do something
Declarative Learning:
Facts about something
Involves
Memorization
Understanding concepts & rules
Acquiring motor skills
Automization
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9. Learning Facilitated Use user’s previous knowledge in interface
By analogy
By structure & organization
If presented in incremental units
Repetition
Use user’s previous knowledge in interface
Hence, I hate PowerPoint 07!
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10. Observations
Users focus on getting job done, not learning to effectively use system
Users apply analogy even when it doesn’t apply
Mac Trashcan for disk eject
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11. Problem Solving Storage in LTM, then application Reasoning
Deductive- If P then Q, P
Inductive- If P then Q, Q
Abductive- Generalization
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12. Observations People are more heuristic than algorithmic
People often choose suboptimal strategies for low priority problems
People learn better strategies with practice
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13. Implications Allow flexible shortcuts
Forcing lengthy, mechanistic plans on user will bore them
Quick Keys! ALT-Q to Quit
Have active rather than passive help
Recognize waste
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14. Language Rule-based Productive Key-word and positional
How do you make plurals?
Productive
We make up sentences
Key-word and positional
Patterns
Should systems have natural language interfaces?
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15. People “Good” “Bad” Infinite capacity LTM Limited capacity STM
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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16. Recap I. Senses II. Information processing A. Sight B. Sound C. Touch
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
C. Motor system
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IAT 334

17. UI Design Principles Categories
Learnability
support for learning for users of all levels
Flexibility
support for multiple ways of doing tasks
Robustness
support for recovery
Always think about exceptions, suitability
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IAT 334

18. Learnability Principles
Predictability
Synthesizability
Familiarity
Generalizability
Consistency
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19. Predictability I think that this action will do…
Operation visibility - can see avail actions
e.g. menus vs. command shell
grayed menu items
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20. Predictable?
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21. Synthesizability
From the resulting system state, My previous action did…
compare in command prompt vs UI
same feedback needed for all users, all apps?
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22. Familiarity Does UI task relate real-world task or domain knowledge?
to anything user is familiar with?
Use of metaphors
pitfalls
Are there limitations on familiarity?
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23. Familiarity
What does the blinking green traffic light mean in Ontario?
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24. Generalizability Does knowledge of one UI apply to others?
Cut and paste in many apps
Does knowledge of one aspect of a UI apply to rest of the UI?
File browsers in MacOS/ Windows
Aid: UI Developers guidelines
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25. Consistency Similar ways of doing tasks
interacting
output
screen layout
Is this always desirable for all systems, all users?
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26. Flexibility Principles
Dialog Initiative
Multithreading
Task migratibility
Substitutivity
Customizability
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27. Dialog Initiative System pre-emptive User pre-emptive
system does all prompts, user responds
sometimes necessary
Eg. Bank machine
User pre-emptive
user initiates actions
more flexible
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28. Multithreading Two types Concurrent Interleaved
input to multiple tasks simultaneously
Interleaved
many tasks, but input to one task at a time
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29. Task migratability
Ability to move performance of task to entity (machine or person) that can do it better
Eg. Autopilot
Spellchecking
When is this good? Bad?
User in control when human decisions are required
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30. Substitutivity Flexibility in details of operations
Allow user to choose suitable interaction methods
Allow different ways to
perform actions
specify data
configure
Allow different ways of presenting output
to suit task, user
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31. Customizability Ability to modify interface By user - adaptability
By system - adaptivity
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32. Robustness Principles
Observability
Recoverability
Responsiveness
Task Conformance
Jan 20, 2011
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33. Observability
Can user determine internal state of system from observable state?
Browsability
explore current state (without changing it)
Reachability
navigate through observable states
Persistence
how long does observable state persist?
Jan 20, 2011
IAT 334

34. Recoverability Ability to continue to a goal after recognizing error
Difficulty of Recovery procedure should relate to difficulty of original task
Forward Recoverability
ability to fix when we can’t undo?
Backward Recoverability
undo previous error(s)
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IAT 334

35. Responsiveness Rate of communication between user and system
Response time
time for system to respond in some way to user action(s)
Stability principle
response time, rate should be consistent
As computers have gotten better, required computer response has gotten shorter
Jan 20, 2011
IAT 334

36. Task Conformance Task coverage Task adequacy
can system do all tasks of interest?
Task adequacy
Can user do tasks?
Does system match real-world tasks?
Jan 20, 2011
IAT 334