Exercise 6.1

Compare and contrast the following two concept pairs.

• Computers vs. Humans
• Developers vs. Users

Exercise 6.2

Identify one good interface and one bad interface and be prepared to explain your choices.

What principles determine whether an interface is good or bad?

6.2.a. Seven Stages of Action

Consider these seven stages of user task execution (D. Norman):

1. Execution
   1. Identifying the goal
   2. Forming the intention to act
   3. Specifying the required system actions
   4. Executing the actions on the system
2. Evaluation
   1. Perceiving the state of the system
   2. Interpreting the state of the system
   3. Determining if the goal is achieved

Where are the problems likely to be? What could we do to make things easier?

6.2.b. A UI Design Model

Exercise 6.3

Human performance exercises

• Memory
• Motor skills
• Reasoning
• Attention

Consider the implications of human performance on the following experiments for UI design.

Exercise 6.3.1

How many chunks of information can a typical human remember?

Exercise 6.3.2

What are the five easiest points on a standard desktop machine to acquire (with the mouse)?

Does this finding apply to mobile phones as well?

Exercise 6.3.3

Exercise 6.3.4

Try this attention experiment.

Exercise 6.4

What are the elements of discount usability?

Are they compatible with agile development methods? If so, how would you combine them; if not, explain why not?