Date of Award


Publication Type

Doctoral Thesis

Degree Name





Psychology, Clinical.




Numerous investigators employing a variety of tasks have found that the pupil of the eye can serve as an index of cognitive effort or processing. Specifically, it has been demonstrated that during cognitive task the pupil dilates in response to stimulus presentation and returns to baseline immediately following solution or task termination. Moreover the increase in pupil size during information processing periods has been found to be positively related to the difficulty level of the task employed. Thus more difficult tasks evoke larger pupillary dilation during processing periods. The consistency of findings in this area has led reviewers to comment that the relationship between pupil size and mental effort is "well-established" and that the pupil is "the best single" physiological measure of processing load. Previous research however has concentrated almost exclusively on the use of 'non-continuous' or short-duration stimuli. That is, tasks have employed digit strings, paired-associate learning, tone discrimination, single word imagery and the like. 'Continuous' stimuli, that is stimuli that provide an extended, contextual and grammatically-integrated information set, such as reading material, have been employed in but two studies, only one of which was concerned with the issue of cognitive effort. Interestingly this isolated study failed to support the relationship function typically obtained. The essential purpose of the present study was to provide added information on how the pupil responds when 'continuous' stimuli are employed. As well the influence of differing levels of 'processing ability' was also investigated. The results obtained support the typical within-task findings of previous studies; that is, the pupil size was sensitive to the presence of processing periods. Mean pupil size did not discriminate between tasks of different difficulty levels but such discrimination was obtained when peak pupil size scores were employed. No convincing support was found for the influence of individual differences in processing ability on the pupillary response. Recommendations were made regarding the need for further and more sophisticated research to support and elaborate the findings here obtained. It was also put forward that if the pupil could be brought under voluntary control through instrumental conditioning procedures then strategies of information presentation could be derived so that learning is facilitated by making such presentation contingent on the presence of 'pupillary states' deemed especially conducive to enhanced information integration and retrieval.Dept. of Psychology. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1980 .W456. Source: Dissertation Abstracts International, Volume: 41-03, Section: B, page: 1129. Thesis (Ph.D.)--University of Windsor (Canada), 1980.