Verbal protocol accuracy in fault diagnosis.

The study examined whether concurrent and retrospective verbal protocols possess the potential to provide a non-reactive and valid account of the cognitive processes involved in fault diagnosis. With this goal in mind, a group of subjects performed a fault diagnosis task under concurrent and retrospective verbalization and in a silent control condition as well. In the task, concurrent verbalization led to a considerable increase in time to completion, but exerted no effect on overall accuracy and the adopted strategy. Retrospective verbalization did not have any effect on performance. The strategy-related data obtained under concurrent verbalization proved to be more valid than those obtained under retrospective verbalization. On the basis of the results it is suggested that, where possible, concurrent verbal reports should be collected when trying to get a better understanding of the nature of the fault diagnostic process.