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Jan 20, 2011IAT 3341 IAT 334 Interface Design Cognitive Aspects (Review) Usability Principles ______________________________________________________________________________________.

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Presentation on theme: "Jan 20, 2011IAT 3341 IAT 334 Interface Design Cognitive Aspects (Review) Usability Principles ______________________________________________________________________________________."— Presentation transcript:

1 Jan 20, 2011IAT 3341 IAT 334 Interface Design Cognitive Aspects (Review) Usability Principles ______________________________________________________________________________________ SCHOOL OF INTERACTIVE ARTS + TECHNOLOGY [SIAT] | WWW.SIAT.SFU.CA

2 Jan 20, 2011IAT 3342 Agenda  Cognitive Processes –Implications –Motor system  Usability Principles –Learnability Principles –Flexibility Principles –Robustness Principles

3 Jan 20, 2011IAT 3343 Basic HCI  Model Human Processor –A simple model of human cognition –Card, Moran, Newell 1983  Components: –Senses –Sensory store –Short-term memory –Long-term memory –Cognition

4 Jan 20, 2011IAT 3344 Model Human Processor Basics  Based on Empirical Data  Three interacting subsystems –Perceptual (read-scan) –Cognitive (think) –Motor (respond)

5 Jan 20, 2011IAT 3345 Information Processing  Usually serial action –Respond to buzzer by pressing button  Usually parallel recognition Driving, reading signs, listening to radio

6 Jan 20, 2011IAT 3346 Processes  Four main processes of cognitive system: –Selective Attention –Learning –Problem Solving –Language

7 Jan 20, 2011IAT 3347 Selective Attention  We can focus on one particular thing –Eg cocktail party talk  Salient visual cues can facilitate s.a. –Examples? –Bold, Larger fonts

8 Jan 20, 2011IAT 3348 Learning  Procedural Learning: –How to do something  Declarative Learning: –Facts about something  Involves –Memorization –Understanding concepts & rules –Acquiring motor skills –Automization

9 Jan 20, 2011IAT 3349 Learning  Facilitated –By analogy –By structure & organization –If presented in incremental units –Repetition  Use user’s previous knowledge in interface –Hence, I hate PowerPoint 07!

10 Jan 20, 2011IAT 33410 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

11 Jan 20, 2011IAT 33411 Problem Solving  Storage in LTM, then application  Reasoning –Deductive-If P then Q, P –Inductive-If P then Q, Q –Abductive-Generalization

12 Jan 20, 2011IAT 33412 Observations  People are more heuristic than algorithmic  People often choose suboptimal strategies for low priority problems  People learn better strategies with practice

13 Jan 20, 2011IAT 33413 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

14 Jan 20, 2011IAT 33414 Language  Rule-based –How do you make plurals?  Productive –We make up sentences  Key-word and positional –Patterns  Should systems have natural language interfaces?

15 Jan 20, 2011IAT 33415 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

16 Jan 20, 2011IAT 33416 Recap  I. Senses –A. Sight –B. Sound –C. Touch  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 –C. Motor system

17 Jan 20, 2011IAT 33417 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

18 Jan 20, 2011IAT 33418 Learnability Principles  Predictability  Synthesizability  Familiarity  Generalizability  Consistency

19 Jan 20, 2011IAT 33419 Predictability  I think that this action will do…  Operation visibility - can see avail actions –e.g. menus vs. command shell –grayed menu items

20 Predictable? Jan 20, 2011IAT 33420

21 Jan 20, 2011IAT 33421 Synthesizability  From the resulting system state, My previous action did… –compare in command prompt vs UI –same feedback needed for all users, all apps?

22 Jan 20, 2011IAT 33422 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?

23 Familiarity  What does the blinking green traffic light mean in Ontario? Jan 20, 2011IAT 33423

24 Jan 20, 2011IAT 33424 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

25 Jan 20, 2011IAT 33425 Consistency  Similar ways of doing tasks –interacting –output –screen layout  Is this always desirable for all systems, all users?

26 Jan 20, 2011IAT 33426 Flexibility Principles  Dialog Initiative  Multithreading  Task migratibility  Substitutivity  Customizability

27 Jan 20, 2011IAT 33427 Dialog Initiative  System pre-emptive –system does all prompts, user responds sometimes necessary Eg. Bank machine  User pre-emptive –user initiates actions more flexible

28 Jan 20, 2011IAT 33428 Multithreading  Two types –Concurrent input to multiple tasks simultaneously –Interleaved many tasks, but input to one task at a time

29 Jan 20, 2011IAT 33429 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?

30 Jan 20, 2011IAT 33430 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

31 Jan 20, 2011IAT 33431 Customizability  Ability to modify interface –By user - adaptability –By system - adaptivity

32 Jan 20, 2011IAT 33432 Robustness Principles  Observability  Recoverability  Responsiveness  Task Conformance

33 Jan 20, 2011IAT 33433 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?

34 Jan 20, 2011IAT 33434 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)

35 Jan 20, 2011IAT 33435 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

36 Jan 20, 2011IAT 33436 Task Conformance  Task coverage –can system do all tasks of interest?  Task adequacy –Can user do tasks? –Does system match real-world tasks?

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