Keep Interaction Results the Same
As mentioned above, consistency in interface behavior is very important. If users experience different
results from the same action, they tend to question their own behavior rather than the product’s
behavior. This leads to users developing superstitious behavior, that is, they think they must do things
in just exactly a certain way for the desired result to happen; otherwise they are not sure of the results.
Sequences of steps and actions should also be consistent throughout a product. I’ve seen products
where users had to logon multiple times to access different parts of the program. This was bad enough,
but it was made worse because the logon process was different each time. Navigation sequences must
also be consistent—don’t use Esc to back up one step in one window and then use Exit in another
window to do the same action.
Standard interface elements must behave the same way. For example, menu bar choices must always
display a drop-down menu when selected. Don’t surprise users by performing actions directly from the
menu bar. Don’t incinerate a discarded object when it is dropped in a waste basket!
Key Idea! If by design, different results might happen than users expect, inform
users before the action is performed. Give them a choice to perform the action,
cancel the operation, or perhaps choose another action to perform.