1. The Design of Everyday Things Darn these hooves! I hit the wrong switch again! Who designs these instrument panels, raccoons?

2. How do you play the CD?

3. Not the “mappings” I would make.

4. Why is this bad?? CD/Tape player –Designed for physical issues rather than usage issues. –Failed to consider logical mappings.

5. The Design of Everyday Things 7 stages of performing an action Conceptual models – the device should explain itself Visibility and Affordances Constraints and Mappings Feedback

6. Seven Stages of Action Goals Evaluation of the interpretations Interpreting the perception Perceiving the state of the world Intention to act Sequence of actions Execution of the action sequence The World

7. Two common places where the process breaks down Goals Evaluation of the interpretations Interpreting the perception Perceiving the state of the world Intention to act Sequence of actions Execution of the action sequence The World GULF OF EXECUTION GULF OF EVALUATION

8. Gulf of Execution Goals Evaluation of the interpretations Interpreting the perception Perceiving the state of the world Intention to act Sequence of actions Execution of the action sequence The World GULF OF EXECUTION

9. The Gulf of Execution Does the system provide actions that correspond to the user’s intentions? The difference between intentions and allowable actions is the Gulf of Execution

10. Gulf of Evaluation Goals Evaluation of the interpretations Interpreting the perception Perceiving the state of the world Intention to act Sequence of actions Execution of the action sequence The World GULF OF EVALUATION

11. The Gulf of Evaluation Does the system provide a physical representation that can be readily perceived and interpreted in terms of the user’s intentions and expectations? The Gulf of Evaluation reflects the amount of effort that the person must exert to interpret the physical state of the system and determine how well the intentions have been met.

12. The Seven Stages as Design aids Determine the function of the system? Tell if the system is in the desired state? Determine a mapping from system state to interpretation Tell what state the system is in? Tell what actions are possible? Determine a mapping from intention to physical action? Perform the action? How easily can the user:

13. Principles for good design Conceptual models Visibility and affordances Mappings Constraints Feedback  Causality Knowledge in the world Standardization Designing for error

14. Conceptual Model People are explanatory creatures – we will come up with models of how things work Rule 1 of interface design – an interface is well designed when it behaves exactly as users think it will Put it another way: the designer’s job is to make it easy for users to create the right model of the system

15. Designer and user models Designer Design Model User User Model System System Image Communication from designer to user is via the system image Goal: user model and design model should be identical So system image must lead user to acquire a user model equal to the design model

16. The notorious case of refrigerator temperature control Two things to control: –Temperature of fresh food compartment –Temperature of freezer compartment

17. Instructions (already a bad sign!) What if I just want to make the freezer warmer?

18. A sensible user model derived from the system image “The Freezer Control controls the freezer temperature and the Fresh Food Control controls the fresh food temperature”

19. But the design model is completely different!

20. And there’s a big problem with feedback, too!

21. So how does a designer help users acquire the right model? Visibility Affordances Constraints Mappings Feedback

22. Visibility Don’t hide controls! –telephones: hold, transfer, 3-way call etc. –VCR programming Make status available –well-designed display (e.g., progress bars) –use sound if needed (click/beep/etc.)

23. Affordances Actual and perceived properties of an object that determine how it could possibly be used –A chair affords sitting –A button affords pushing –A knob affords turning –A slot affords sticking things in

24. Affordances in GUIs? Does a button icon afford clicking? Maybe… but what does the click mean? Meaning is arbitrary, and is assigned by designers Norman: “‘I put an affordance there… I wonder if the object affords clicking…’ affordances this, affordances that. And no data, just opinion. Yikes! What had I unleashed upon the world?” Bottom line – affordances aren’t as useful in GUIs as in physical design

25. Mappings Mappings used to determine relationships –Between actions and results –Controller and controlled Take advantage of physical analogies and cultural standards

26. Which dial controls which burner?

29. Which knob controls which burner?

31. Why don’t all stoves use this design? Is it ugly? More expensive? Less safe? …?

32. Constraints Limit the range of possible actions Physical Constraints –Only some possibilities are physically possible (only one way to put a VCR tape in a player) Semantic Constraints –Only some possibilities make sense Cultural Constraints –Only some possibilities are acceptable Logical Constraints –General principles: e.g., every part should be used

33. Feedback Remember that people will build models –And feedback leads to causal models: “if Y happened after X, then X caused Y” So provide the proper feedback immediately: respond to user actions – don’t hide the results! –Did I press the button? (visual and/or audio feedback) All actions should have effects –Promote exploration

34. Next Steps Next class –If you haven’t done so, finish DOET. Project –Groups should be forming and projects selected –Can’t find others to work with, no ideas interest you, other problems? Talk to me at once –Friday – Initial Proposal due, but we won’t do studio on this until next week.