IAT 334 Interface Design Cognitive Aspects Review Usability

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

Agenda g Cognitive Processes – Implications – Motor system g Usability Principles – Learnability Principles – Flexibility Principles – Robustness Principles Jan 20, 2011 IAT 334 2

Basic HCI g Model Human Processor – A simple model of human cognition – Card, Moran, Newell 1983 g Components: – – – Senses Sensory store Short-term memory Long-term memory Cognition Jan 20, 2011 IAT 334 3

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

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

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

Selective Attention g We can focus on one particular thing – Eg cocktail party talk g Salient visual cues can facilitate s. a. – Examples? – Bold, Larger fonts Jan 20, 2011 IAT 334 7

Learning g Procedural Learning: – How to do something g Declarative Learning: – Facts about something g Involves – Memorization – Understanding concepts & rules – Acquiring motor skills – Automization Jan 20, 2011 IAT 334 8

Learning g Facilitated – By analogy – By structure & organization – If presented in incremental units – Repetition g Use user’s previous knowledge in interface – Hence, I hate Power. Point 07! Jan 20, 2011 IAT 334 9

Observations g Users focus on getting job done, not learning to effectively use system g Users apply analogy even when it doesn’t – Mac Trashcan for disk eject Jan 20, 2011 IAT 334 10

Problem Solving g Storage in LTM, then application g Reasoning – Deductive- If P then Q, P – Inductive- If P then Q, Q – Abductive- Generalization Jan 20, 2011 IAT 334 11

Observations g People are more heuristic than algorithmic g People often choose suboptimal strategies for low priority problems g People learn better strategies with practice Jan 20, 2011 IAT 334 12

Implications g Allow flexible shortcuts – Forcing lengthy, mechanistic plans on user will bore them – Quick Keys! ALT-Q to Quit g Have active rather than passive help – Recognize waste Jan 20, 2011 IAT 334 13

Language g Rule-based – How do you make plurals? g Productive – We make up sentences g Key-word and positional – Patterns g Should systems have natural language interfaces? Jan 20, 2011 IAT 334 14

People g “Good” – Infinite capacity LTM – LTM duration & complexity – High-learning capability – Powerful attention mechanism – Powerful pattern recognition Jan 20, 2011 g “Bad” – Limited capacity STM – Limited duration STM – Unreliable access to LTM – Error-prone processing – Slow processing IAT 334 15

Recap g I. Senses – A. Sight – B. Sound – C. Touch g 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 Jan 20, 2011 IAT 334 16

UI Design Principles g Categories – Learnability • support for learning for users of all levels – Flexibility • support for multiple ways of doing tasks – Robustness • support for recovery g Always Jan 20, 2011 think about exceptions, suitability IAT 334 17

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

Predictability g. I think that this action will do… g Operation visibility - can see avail actions – e. g. menus vs. command shell – grayed menu items Jan 20, 2011 IAT 334 19

Predictable? Jan 20, 2011 IAT 334 20

Synthesizability g 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 21

Familiarity g 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 22

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

Generalizability g Does knowledge of one UI apply to others? – Cut and paste in many apps g Does knowledge of one aspect of a UI apply to rest of the UI? – File browsers in Mac. OS/ Windows g Aid: Jan 20, 2011 UI Developers guidelines IAT 334 24

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

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

Dialog Initiative g System pre-emptive – system does all prompts, user responds • sometimes necessary • Eg. Bank machine g User pre-emptive – user initiates actions • more flexible Jan 20, 2011 IAT 334 27

Multithreading g Two types – Concurrent • input to multiple tasks simultaneously – Interleaved • many tasks, but input to one task at a time Jan 20, 2011 IAT 334 28

Task migratability g Ability to move performance of task to entity (machine or person) that can do it better – Eg. Autopilot – Spellchecking – When is this good? Bad? Jan 20, 2011 IAT 334 29

Substitutivity g 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 30

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

Robustness Principles g Observability g Recoverability g Responsiveness g Task Jan 20, 2011 Conformance IAT 334 32

Observability g 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 33

Recoverability g 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 34

Responsiveness g 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 35

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