interaction
Gulf of execution / evaluation
The two gaps a user has to cross – between what they intend and what the interface lets them do, and between what happened and how well they understand it.
Norman’s model of every interaction as two bridges. The gulf of execution: I know what I want – can I work out how to do it here? The gulf of evaluation: I did something – can I tell what just happened?
Good design narrows both. Clear affordances and signifiers shrink the execution gulf; immediate, proportionate feedback shrinks the evaluation gulf (click a button, see it respond within ~100ms, even before the real result arrives). When you hear a user say “I don’t know what it’s doing”, that’s the evaluation gulf yawning open – and it’s a design defect, not a user failing.