As a test of the hypothesis that pupil dilation during performance is partially due to a task related anxiety component, pupillary patterns were measured while subjects (Ss) processed digit strings of various lengths for immediate recall. Information overload resulted in a leveling of the dilation pattern which suggested a momentary suspension of processing effort. In addition, significant correlations were observed between individual differences in pupil size and recall performance.

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A study was conducted to assess pupil constriction as a reflection of fatigue in an industrial environment. Subjects were telephone operators who were participating in a trial of an automated retrieval and display device (microfilm) for directory assistance operation. Eleven subjects were tested before and after working on the traditional telephone book as well as on the mechanical device. The testing consisted of photographing the subjects' pupil at a rate of two frames per second for three minutes. A significant difference was found in the mean pupil diameter between pre-and postwork measures across work conditions. Results indicated that the technique may be useful for determining relative fatigue levels.

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