Ascertaining changes in cognitive correlates of learning as students advanced through hierarchical instruction, 24 individual difference measures were obtained from 166 Navy trainees who had completed a computer-managed mastery course in electricity and electronics. Three types of cognitive characteristic measures were used in the study--tests of cognitive styles, abilities, and aptitudes. The instructional treatment consisted of the first 11 modules of the Basic Electricity/Electronics School curriculum. This involved computer managed instruction (CMI) to implement the mastery learning of the subject matter of the modules. The students self-studied and self-paced themselves through lesson modules off-line. From the tests of cognitive characteristics, principal component analysis and varimax rotation were computed, producing factor scores which were used in multiple regression analyses to predict achievement in the 11 modules of instruction. Results indicated that considerable changes occurred in the cognitive predictors of achievement as students progressed through the modules. During the acquisition of course content, the cognitive components sampled shifted noticeably in importance throughout the curriculum. These results seemed to imply that it is not only the content of instruction which matters, but also the task demanded of the students as they progress through the course that determine the nature of the relationship of cognitive style to achievement. The results have implications for research on transition from novice to expert, crystallized and fluid intelligence, task demands of instruction, and computer-managed mastery learning. (Author/KC)