Usability

When errors occur in the use of a product, people shouldn’t blame themselves, but should instead put the fault on the design and the designer. The designer, in turn, should take this responsibility for error seriously.

A user relies on the system image of a product to form an understanding of how to use it, so the designer’s conceptual model needs to be carefully and thoughtfully mapped to the system image.

The Gulf of Evaluation describes the potential issues that arise from the discrepancy between the current state of the system and the user’s perceptions of it. Designers can narrow the gap through the use of natural mapping and clear feedback.

The Gulf of Execution describes the potential issues that arise from the discrepancy between the user’s intention and the possible actions they can take. Designers can narrow the gap with visible affordances and considered constraints.

Enjoyable experiences carry a common set of attributes, including a challenge matched against a person’s skill, clear goals and feedback, a sense of control, and a complete absorption of attention.