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
Jan 20, 2011IAT 3344 Model Human Processor Basics Based on Empirical Data Three interacting subsystems –Perceptual (read-scan) –Cognitive (think) –Motor (respond)
Jan 20, 2011IAT 3345 Information Processing Usually serial action –Respond to buzzer by pressing button Usually parallel recognition Driving, reading signs, listening to radio
Jan 20, 2011IAT 3346 Processes Four main processes of cognitive system: –Selective Attention –Learning –Problem Solving –Language
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
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
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!
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
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
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
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
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?
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
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
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
Predictable? Jan 20, 2011IAT 33420
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?
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?
Familiarity What does the blinking green traffic light mean in Ontario? Jan 20, 2011IAT 33423
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
Jan 20, 2011IAT 33425 Consistency Similar ways of doing tasks –interacting –output –screen layout Is this always desirable for all systems, all users?
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
Jan 20, 2011IAT 33428 Multithreading Two types –Concurrent input to multiple tasks simultaneously –Interleaved many tasks, but input to one task at a time
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?
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
Jan 20, 2011IAT 33431 Customizability Ability to modify interface –By user - adaptability –By system - adaptivity
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?
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)
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
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?