Donald Norman's Gulf of Execution and Evaluation Model

The gulf of execution and evaluation, or cognitive gulf, was described by usability expert Donald Norman in his 1988 book The Design of Everyday Things. Norman referred to it as the difference between people's intentions and their ability to execute their intentions. 

Gaps like this are usually a result of failure on the part of products to have clear directions on how to use them or their lack of quality feedback mechanisms. It is recommended to be used in stakeholders performance domain and delivery performance domain.

What is Gulf of Execution?

In his ground-breaking book, The Design of Everyday Things, Donald Norman wrote about the gulfs of execution and evaluation. The gulfs refer to the distance between a user's current state and the state in which they wish to be. The gulf of execution is the gap between what the user desires to do and how they carry out that intent. When a person performs an action, he or she may have in mind certain expectations for that action. If those expectations are not met, then there is a gulf of execution.  For example, a person might think that because he has pressed a button on a remote control that the TV will turn off. But if the remote control does not work because of technical problems with the TV itself, there is still a gulf of execution. Conversely, if pressing the button on the remote control were enough to turn off the TV without any other steps being required on behalf of the user (for example, waiting for several seconds), then there would be no gulf of execution.

What is Gulf of Evaluation?

The gulf of evaluation is the gap between an external stimulus and a person's interpretation of it. In simple words, the gulf of evaluation is the difficulty of judging the state of the system and how well the artifact aids the discovery and interpretation of that state.  If, for instance, you are using a TV remote control with an on/off button, the gulf of evaluation is very small because with just one switch, the user will know immediately whether their action was successful or not.