Pupillary changes during encoding, storage, and retrieval of information.

6 subjects were each auditorily presented six lists of 7-digit numbers for retention intervals of 0, 5, and 10 sec. Pupil size was recorded during stimulus presentation, retention, interval, and recall of items. Results indicated that pupil dilation occurred during encoding and retrieval of stimulus items. Pupillary constriction was found during the retention interval when rehearsal was presumed to occur.