Research on the use of eye movement indices (such as number of fixations, the average fixation duration, and saccadic movements) as a measure of cognitive processing is reviewed in this paper. Information is provided on the physiology of the eye, computer applications to eye movement study, the influence of stimulus materials and intelligence on eye movement, and the relationship between cognitive processes, visuals, and learning to give a more complete understanding of how the eye and eye movement studies may be used to help design more effective visuals for learning. (MKM)