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Cognitive Aspects (Review) Usability Principles

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Presentation on theme: "Cognitive Aspects (Review) Usability Principles"— Presentation transcript:

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 Jan 20, 2011 IAT 334

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 Jan 20, 2011 IAT 334

4 Model Human Processor Basics
Based on Empirical Data Three interacting subsystems Perceptual (read-scan) Cognitive (think) Motor (respond) Jan 20, 2011 IAT 334

5 Information Processing
Usually serial action Respond to buzzer by pressing button Usually parallel recognition Driving, reading signs, listening to radio Jan 20, 2011 IAT 334

6 Processes Four main processes of cognitive system: Selective Attention
Learning Problem Solving Language Jan 20, 2011 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 Jan 20, 2011 IAT 334

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 Jan 20, 2011 IAT 334

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! Jan 20, 2011 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 Jan 20, 2011 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 Jan 20, 2011 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 Jan 20, 2011 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 Jan 20, 2011 IAT 334

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? Jan 20, 2011 IAT 334

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 Jan 20, 2011 IAT 334

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 Jan 20, 2011 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 Jan 20, 2011 IAT 334

18 Learnability Principles
Predictability Synthesizability Familiarity Generalizability Consistency Jan 20, 2011 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 Jan 20, 2011 IAT 334

20 Predictable? Jan 20, 2011 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? Jan 20, 2011 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? Jan 20, 2011 IAT 334

23 Familiarity What does the blinking green traffic light mean in Ontario? Jan 20, 2011 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 Jan 20, 2011 IAT 334

25 Consistency Similar ways of doing tasks
interacting output screen layout Is this always desirable for all systems, all users? Jan 20, 2011 IAT 334

26 Flexibility Principles
Dialog Initiative Multithreading Task migratibility Substitutivity Customizability Jan 20, 2011 IAT 334

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 Jan 20, 2011 IAT 334

28 Multithreading Two types Concurrent Interleaved
input to multiple tasks simultaneously Interleaved many tasks, but input to one task at a time Jan 20, 2011 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? User in control when human decisions are required Jan 20, 2011 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 Jan 20, 2011 IAT 334

31 Customizability Ability to modify interface By user - adaptability
By system - adaptivity Jan 20, 2011 IAT 334

32 Robustness Principles
Observability Recoverability Responsiveness Task Conformance Jan 20, 2011 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? 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) Jan 20, 2011 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

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