When people use something, they face two gulfs: the Gulf of Exe- cution, where they try to figure out how it operates, and the Gulf of Evaluation, where they try to figure out what happened (Fig- ure 2.1). The role of the designer is to help people bridge the two gulfs.
In the case of the filing cabinet, there were visible elements that helped bridge the Gulf of Execution when everything was work- ing perfectly. The drawer handle clearly signified that it should be pulled and the slider on the handle indicated how to release the catch that normally held the drawer in place. But when these oper- ations failed, there then loomed a big gulf: what other operations could be done to open the drawer?
The seven-stage action cycle is simplified, but it provides a use- ful framework for understanding human action and for guiding design. It has proven to be helpful in designing interaction. Not all of the activity in the stages is conscious. Goals tend to be, but even they may be subconscious. We can do many actions, repeatedly cycling through the stages while being blissfully unaware that we are doing so. It is only when we come across something new or reach some impasse, some problem that disrupts the normal flow of activity, that conscious attention is required.
Most behavior does not require going through all stages in se- quence; however, most activities will not be satisfied by single ac- tions. There must be numerous sequences, and the whole activity may last hours or even days. There are multiple feedback loops in which the results of one activity are used to direct further ones, in which goals lead to subgoals, and plans lead to subplans. There are activities in which goals are forgotten, discarded, or reformulated.