IAT 334 Interface Design

1. IAT 334Interface Design Cognitive Aspects (Review) Usability Principles ______________________________________________________________________________________SCHOOL OF INTERACTIVE ARTS + TECHNOLOGY [SIAT] | WWW.SIAT.SFU.CA IAT 334

2. Agenda • Cognitive Processes • Implications • Motor system • Usability Principles • Learnability Principles • Flexibility Principles • Robustness Principles IAT 334

3. 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 IAT 334

4. Model Human Processor Basics • Based on Empirical Data • Three interacting subsystems • Perceptual (read-scan) • Cognitive (think) • Motor (respond) IAT 334

5. Information Processing • Usually serial action • Respond to buzzer by pressing button • Usually parallel recognition • Driving, reading signs, listening to radio IAT 334

6. Processes • Four main processes of cognitive system: • Selective Attention • Learning • Problem Solving • Language IAT 334

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 IAT 334

8. Learning • Procedural Learning: • How to do something • Declarative Learning: • Facts about something • Involves • Memorization • Understanding concepts & rules • Acquiring motor skills • Automization IAT 334

9. 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! IAT 334

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 IAT 334

11. Problem Solving • Storage in LTM, then application • Reasoning • Deductive- If P then Q, P • Inductive- If P then Q, Q • Abductive- Generalization IAT 334

12. Observations • People are more heuristic than algorithmic • People often choose suboptimal strategies for low priority problems • People learn better strategies with practice IAT 334

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 IAT 334

14. Language • Rule-based • How do you make plurals? • Productive • We make up sentences • Key-word and positional • Patterns • Should systems have natural language interfaces? IAT 334

15. “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 People IAT 334

16. 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 Recap 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 IAT 334

18. Learnability Principles • Predictability • Synthesizability • Familiarity • Generalizability • Consistency IAT 334

19. Predictability • I think that this action will do… • Operation visibility - can see avail actions • e.g. menus vs. command shell • grayed menu items IAT 334

20. Predictable? IAT 334

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? IAT 334

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? IAT 334

23. Familiarity • What does the blinking green traffic light mean in Ontario? IAT 334

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 IAT 334

25. Consistency • Similar ways of doing tasks • interacting • output • screen layout • Is this always desirable for all systems, all users? IAT 334

26. Flexibility Principles • Dialog Initiative • Multithreading • Task migratibility • Substitutivity • Customizability IAT 334

27. Dialog Initiative • System pre-emptive • system does all prompts, user responds • sometimes necessary • Eg. Bank machine • User pre-emptive • user initiates actions • more flexible IAT 334

28. Multithreading • Two types • Concurrent • input to multiple tasks simultaneously • Interleaved • many tasks, but input to one task at a time IAT 334

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? IAT 334

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 IAT 334

31. Customizability • Ability to modify interface • By user - adaptability • By system - adaptivity IAT 334

32. Robustness Principles • Observability • Recoverability • Responsiveness • Task Conformance IAT 334

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? 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) 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 IAT 334

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