Key points are not available for this paper at this time.
The mental procedures used by skilled electronics repair men in their normal working environment have been studied by analysis of verbal protocols. The procedures found are organized as a search through a system which is viewed as a hierarchy of subunits. The general structure of the search can be broken down into a sequence of recurrent search routines. Basically different types of such routines are found with great differences in respect to the number of observations needed and the complexity of the mental data processing involved. They also differ greatly with respect to the depth of knowledge of the internal functioning of the system used by the repair men. The records demonstrate a great ability by the men to conduct the search by general routines mostly depending upon their general professional background, and a preference for rapidstreams of simple decisions giving good or bad judgements regardless of whether observations are informationally redundant or not. Seen from the viewpoint of information economy, the procedures are inefficient, but if the men are supposed to minimize the time spent in the task and the mental load involved, the procedures are very rational. The records indicate that the men have great confidence in the experience that the general routines will ultimately lead them to the fault. In cases where they are unsuccessful, there seems to be a fixation, resulting in a tendency to rely on repetitions, rather than to generate specific procedures based upon reasoning related to the functioning of the specific system.
Rasmussen et al. (Wed,) studied this question.