Convenient evaluation of mental stress with pupil diameter.

This study proposes a convenient method of evaluating mental stress. The potential of monitoring changes in pupil diameter as a measure of human reliability while operating human-machine systems was examined experimentally. An experiment was carried out to clarify the relation between changes in pupil diameter and autonomic nervous activity by measuring an electrocardiogram and pupil diameter when 10 subjects completed a time-sensitive task. The electrocardiogram was measured using a multitelemeter system and pupil diameter was measured using an eye-mark recorder. Several relationships between changes in pupil diameter and autonomic nervous activity were revealed and indicated that measurement of pupil diameter was an effective indicator of autonomic nervous activity. Therefore, it may be possible to develop a monitoring system that measures changes in pupil diameter as an indicator of the mental state of workers operating human-machine systems.