Dyslexic and normal readers' eye movements.

Dyslexic and normal readers' eye movements were compared while tracking a moving fixation point and in reading.Contrary to previous reports, the dyslexic and normal readers did not differ in their number of saccades, percentage of regressions, or stability of fixations in the tracking task.Thus, defective oculomotor control was not associated with or a causal factor in dyslexia, and the dyslexics' abnormal eye movements in reading must be related to differences in higher cognitive processes.However, individual differences in oculmotor efficiency, independent of reading ability, were found within both the dyslexic and normal groups, and these differences were correlated in reading and tracking tasks. As part of an analytic approachto the study of reading processes, increasing attention is being directed toward developmental and individual differences (Baron & Strawson, 1976; LaBerge & Samuels, 1974; Perfetti, in press; Stanovich, 1982; Vellutino, 1983).Dyslexia is an extreme expression of individual differences in reading skill wherein children and adults are substantially retarded in reading, in spite of their normal IQ and education.The present study asks whether the abnormal eye movements commonly observed during reading in dyslexics are a cause of their reading problems because of general difficulties in oculomotor control or whether they arise from difficulties in verbal processes and are only observed during reading.This question has a long history, and the different answers have centered around different theories regarding the etiology of dyslexia.Dyslexia has been variously ascribed to difficulties in visual processes or verbal pro-