Gulfs of Execution and Evaluation
Two gaps break interfaces: not knowing how to do the thing, and not knowing whether it worked.
Definition
From Norman's seven stages of action. The gulf of execution is the gap between a user's goal and the actions the system makes available. The gulf of evaluation is the gap between the system's state and the user's ability to interpret it.
Expert heuristic. A review criterion developed by practitioners. Useful and widely taught, but evaluated by judgement rather than measurement.
On this page
A diagnostic, not a rule
The value of this model is in diagnosis. When a user fails, ask which gulf they fell into. If they did not know what to do, it is execution, and the fix is signifiers, labels, discoverability and mapping. If they did the right thing and could not tell whether it worked, it is evaluation, and the fix is feedback, status and clearer state representation.
Teams routinely apply the wrong fix. Adding a tour to an evaluation problem, or better confirmation messages to an execution problem, leaves the failure in place.
Norman's seven stages, in short
- 1
Goal
The user forms an intention about the world, not about the interface.
- 2
Plan
They decide on a sequence of actions.
- 3
Specify
They translate the plan into specific operations the system offers.
- 4
Perform
They execute the operations. Stages two to four are the gulf of execution.
- 5
Perceive
They notice the system's response.
- 6
Interpret
They work out what the response means.
- 7
Compare
They judge the result against the goal. Stages five to seven are the gulf of evaluation.
In practice
Silent save
EditorsUsers pressing save repeatedly is an evaluation failure. They performed the correct action and the system gave them nothing to interpret.
Invisible bulk selection
ListsUsers deleting items one at a time when a bulk action exists is an execution failure. Better confirmation messages would not touch it.
Sources
Where a source establishes something narrower than the popular reading of it, the note says so.
The Design of Everyday Things
D. A. Norman, Basic Books, 1988, revised 2013
User Centered System Design
D. A. Norman and S. W. Draper, Lawrence Erlbaum, 1986
Where the gulfs were first set out.
Continue from here
Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.
Applied through
Where this shows up as a concrete interface decision.
- Heuristic EvaluationResearch method
- Usability TestingResearch method
Related concept
Connected closely enough to change how you apply this.
- Visibility of System StatusHeuristic
- Affordances and SignifiersPrinciple
- DiscoverabilityPrinciple
- FeedbackPrinciple