How can user interface designers determine whether a user interface (element) will cause problems for users?

1. Analyze the interface using "common sense" (?)

• Intuitions can reveal some obvious omissions, confusing and inefficient interaction.
• Many flaws however are not "intuitively" recognizable, even with experience in user interface design.
   

2. Develop a theory of "human cognitive processing", and use it to predict problems that users will have with the interface

• Was only successfull in limited areas so far.

3. Develop a theory of neuronal correlates of HCI concepts ('ease of use', 'usefulness'), and watch the neuronal activity of test users working with the interface

• Emerging research field
• Only very coarse results so far (they refer to the whole interface and do not allow to identify the blamable interface elements).

4. Test the interface with users, and watch whether problems can be observed or are reported by users

•  Tests with 5-8 users already reveal major problems
•  Generalize the findings from (4) and develop guidelines of what should not be done
     "Usability Engineering"
  

How can user interface designers determine whether a user interface (element) will not cause problems for users?