Good Design

2. Good Design • Visibility is key to interaction design • Take advantage of affordances/constraints • Provide a good conceptual model for the user

3. Mental models • People form mental models of things they interact with Design model User’s model Designer User System System image

4. Mental models • People form mental models of things they interact with • When the number of possible actions exceeds the number of controls, there will be difficulty • Added functions mean added difficulty

5. Mental models • People form mental models of things they interact with • When the number of possible actions exceeds the number of controls, there will be difficulty • Added functions mean added difficultyQUICK! How do you take a screenshot on an iPhone?

6. Natural mappings • Natural mappings are made of win • Spacial • Cultural/biological • Following principles of perception • Additive dimensions:amount, loudness, weight, line length, brightness • Substitutive dimensions:pitch, taste, colour, location

7. Seven stages of action • Forming the goal • Forming the intention • Specifying an action • Executing the action • Perceiving the state of the world • Interpreting the state of the world • Evaluating the outcome Execution Evaluation

8. Errors • Everyone makes mistakes – designers make the mistake of not taking errors into account

9. Errors Types of error: • Mistakes: when you form the wrong goal • Slips: when you form an appropriate goal but mess up the performance • Types of slips:capture errors, description errors, data-driven errors, associative activation errors, loss-of-activation errors, mode errors

10. Errors Why we make mistakes: • Human thought is based on past experiences • Decision trees: width + depth = difficulty • Ice-cream menu = wide and shallow • Cookbook recipe = deep and narrow • Chess = oh God oh God oh God oh God oh God (Width and depth are often found in games)

11. Errors • Designers should make errors as cost-free as possible • Errors should be easy to detect, have minimal consequences, and be reversible

12. Errors Forcing functions are made of win • Interlocks force proper sequence • Lockins keep an operation active • Lockouts keep people out of danger Forcing functions can be a right nuisance though

13. Psychology We have two kinds of knowledge • Knowledge of (declarative):Facts and rules, easy to write and teach • Knowledge how (procedural):Best learned by practice

14. Psychology We have three different types of memory • For arbitrary info • For meaningful relationships • For memory through explanation Rule of thumb If a design depends upon labels, it may be faulty.

15. Psychology Precise behaviour can emerge from imprecise knowledge if: • The necessary information is in the world • Precision is not required • Natural constraints are in effect • Cultural constraints are in effect Knowledge in the head can be more efficient, but it requires learning, which can be hard 

16. Constraints There are four classes of constraints: • Physical • Semantic • Cultural • Logical

17. Questions that guide our interactions: • Which parts move? • What part is to be manipulated? • What movement is possible? • What are the relevant physical characteristics of the movement?(How hard, how far...) • What parts are supporting surfaces? How much size and weight will it support?

18. Problems of design • Once it works, refinement may be counterproductive • Users are often experts at the task, designers are experts at the device • There is no such thing as the average person – design for flexibility/adjustability • Account for handicaps, old age, physique, etc.

19. Problems of design • Don’t focus on either satefy, usability, aesthetics, or manufacturability to the exclusion of the others • Avoid feature creep by cutting features or by organising and modularising them • Don’t worship false idols complexity

20. Explorable systems • User must readily see and be able to do the allowable actions in each system state • The effect of each action must be both visible and easy to interpret • Actions should be without cost

21. Computer systems • Two modes of computer usage: • Third person: issue commands • First person: direct manipulation • Make the computer system invisible

22. Left-over points • Simplifying the structure of tasks: • Provide mental aids • Use technology to make visible what would be invisible, improving feedback • Automate but keep tasks the same • Change the nature of the task • When automating, don’t take away control • Some things should be difficult • Difficulty and challenge ≠ frustration and error