The Gulfs of Execution and Evaluation
When people use something they face two gulfs; the designer's job is to help bridge both.
- Gulf of Execution — figuring out how to operate it ("What can I do? How?"). Bridged by Signifiers, constraints, mappings, and a conceptual model — i.e., feedforward.
- Gulf of Evaluation — figuring out what happened and whether the goal was reached ("What state is it in?"). Bridged by feedback and a conceptual model. See Feedback and Feedforward.
Definition detail: the Gulf of Evaluation reflects how much effort the person must spend to interpret the device's state and judge whether intentions were met. The gulf is small when the device presents its state in a form that is easy to get, easy to interpret, and matches how the person thinks about the system.
Illustration: the stuck filing-cabinet drawer (ch.2 opening) — the landlady could bridge the gulfs in normal use (handle signifies pulling) but had no idea what to do once the normal operation failed, and falsely blamed herself.
The gulfs map directly onto the The Seven Stages of Action: execution = plan/specify/perform; evaluation = perceive/interpret/compare. Each gulf is an opportunity for product improvement.
Confidence
1.0 — explicit named concept.
Sources: ["DOET ch.2 'The Gulfs of Execution and Evaluation' p.38-40 (Fig 2.1)"]