A study of the use of the half-split method of locating trouble sources in malfunctioning equipment. Found that where the system relationships are easily mastered this method is an aid to efficiency. In complex systems, however, S needs either relatively high ability or instructional aid to overcome the load put on his capacities. Concluded that deductive ability is a prerequisite for the application of this method and may play a major role at each stage of a trouble-shooting task. (PsycINFO Database Record (c) 2006 APA, all rights reserved)