This paper reports on a study concerned with rapid mental operations of the central processor as it performs tasks such as the comparison of rotated figures, mental arithmetic, sentence verification, and memory scanning. The central processor is the site of most of the symbol manipulation that takes place in the human information processing system. One of the goals of the study is to demonstrate that the locus, duration and sequence of eye fixations are all closely tied to the activity of the central processor. The research is intended to discover how eye fixations are related to cognitive processes, the aim being to construct a theory of that relationship that generalizes across a number of task environments. The second goal of the research is to examine how the eye fixation data reveals the fine structure of the processor's activity in performing a number of cognitive tasks. (Author/CLK)