It’s not your fault.
Design Principles – Conceptual models, feedback, constraints, affordances, mapping, visibility
Power of observationDesign is communicationFalse causality
Principles of design for understandability and usability – conceptual model & visibilityMental model, designer’s model, system image, users model
The paradox of technology Naive physics and psychology might be wrong but are often sensible
Learned helplessnessTaught helplessness
7 stages of action – goal, intention, action sequence, execution, perception, interpretation, evaluationOpportunistic vs planned actions
The gulf of executionThe gulf of evaluation
Knowledge resides partly in the head, the world and the constraints of the world., cultural constraints Discrepancy in precision of behavior and imprecision of knowledgePrecise behavior from imprecise knowledgeDeclarative knowledge and procedural knowledge
Memory usage – memory for arbitrary things, memory for meaningful relationships, memory through explanation
Wherever labels are necessary, consider another design
Tradeoff between knowledge in the world and head – retrievability, learning, efficiency of use, ease of first time use, aestheticsConstraints – physical, semantic, cultural, logical
If a door handle needs a sign, then its design is probably faulty
Switches – grouping problem, mapping problem
Sounds must reflect the natural relationships when providing feedback
Errors – Slips (mess up action sequence) & mistakes (form wrong goal)
Types of slips – capture error, description error, data driven error, associative activation error, loss of activation error, mode error
Detection of slips – need feedback, also need to know error level
Design lessons from study of slips – Prevention., CorrectionIf you build an error tolerant system, people will rely on it, so it needs to be reliable.
Mistakes:
Models of human thought – files, schema theory, connectionism/neural models-common memory & a discrepant. Tend to remember the latter, former is bunched together to form an average
Structure of tasks:Wide and deep structure (Chess)Shallow structure (food menu)Narrow structure (starting a car)
Everyday activities must minimize planningGames, puzzles, novels use wide and deep structures to make it more engaging
Conscious and subconscious behaviorConscious thought has limited short term memory. It can be overcome by providing it an organizational structure that makes use of our subconscious pattern matching memory
It is a lot easier to determine the obvious after the mistake has happened. Mistakes happen often when we misinterpret a situation. We explain away errors with logical explanation once it has occurred.
Social pressure & mistakesCannot discount the effect of social pressures on decisions that are mistakes.
Designing for errorNormal behavior is not always accurate and therefore you must design for error. Do not punish people for.making error. Design the system to allow for errors. Nderstamd the caues of error and design to minimize it. Allow actions to be undone if error occurs or if not possible make those actions hard to do. Make error discovery and error correction easier.
Warning signals that can’t distinguish between deliberate and erroneous actions is poor design. Forcing functions – physical constraints on actions – failure in one stage prevents next stage from happening. But it isn’t easy to force unwanted behavior on users. FF – specialized methods for preventing accidents – interlocks(forces action to take place in a proper sequence), lockin(keeps operation active, & stops anyone from prematurely stopping it) , lockout (prevents an event from occurring or someone from entering a place that is dangerous)
Natural evolution of design – hill climbingForces working against evolutionary design:- new models are in the design process before the old ones are released- no feedback mechanisms- pressure to be distinctive- curse of the designers individuality
Why designers go astray- putting aesthetics first- designers are not typical users (repeated use of product results in the knowledge in the head whereas first time users rely on knowledge in the world) – designer’s clients may not be users – designing for special people- selective attention (problem of focus)
Design is the successive application of constraints until a unique product is left.
Designer must balance different constraints – market, cost, aesthetics, usability etc
Physical anthropometry – measurement of the human individual
Two deadly temptations for the designer :- creeping featurism: tendency to add features beyond reason. Two ways to deal with it… avoidance /restraint and organization /modularization- worshipping of false images
Explorable systems must have 3 requirements :- visibility of allowable actions- effect of action must be visible & easy to interpret- actions should be without cost
Make the computer system invisible when doing a task
User centered design:
Design should make sure that (1) user can figure out what to do (2) user can tell what is going on
7 principles for transforming difficult tasks to simple ones :
- Use knowledge in the world and in the head3 conceptual models – designer’s, user’s, system image.designer and user communicate through system.image.
- Simplify structure of tasksUsing tech – keep task the same but provide mental aids – to make invisible visible, improving feedback & ability to keep control (computer graphics) – automate but keep nature of task same. (Car auto transmission) – change nature of task if itnis complex (shoelace to Velcro for kids & elderly) – don’t take away control (over automation can be a problem – overreliance, system failure, takes away control)
First 2 act as reminders keeping the task the same
Technology can transform deep, wide structures into narrower and shallower ones.
Task simplification by itself, is not necessarily a virtue.
- Make things visible : bridge gaps between execution and evaluation
Enable user to determine relationships :- between intentions & possible actions- b/w actions and its effects- b/w actual system state & what is the perceived system state- b/w perc. state & intentions, needs, expectations
- Get the mappings right5. Exploit the power of constraints – natural & artificial6. Design for error7. If all else fails, standardize.Standardization is another aspect of cultural constraints
Deliberately making things difficult through design for safety, security etc :- hide critical components (make things invisible) – unnatural mappings for execution and evaluation- make actions physically difficult to do- require precise timing & physical manipulation- no feedback
Easy looking is not necessarily easy to use
Complexity of appearance = no of controlsDifficulty of use = difficulty of finding controls + difficulty of executing functions
For ease to use, match no of controls to no of functions and organize panel acc to function For looking easy to use, minimize no of controls. Hide controls not being used at the moment.
We are surrounded by objects of desire, not objects of use.
