Pupil dilation as indicative of cognitive workload while driving a car: effects of cell phone use and driver experience in young adults

BACKGROUND: Cognitive workload resulting from drivers’ engagement in concomitant tasks while driving, such as talking on a cell phone, affects the availability of attentional resources for the various stages of information processing, which can interfere with the selection of relevant traffic information, leading to poor performance and higher risk of accidents.

AIM: The purpose of this study was to test the adaptation and application of the method of fixation-aligned pupillary response averaging to the car driving context, and, if successful, to determine effects of talking on a cell phone while driving, in both handheld and hands-free situations, and effects of driving experience on pupillary responses of young adult drivers, as indicative of cognitive workload.

METHOD: Ten novice and ten experienced drivers had pupil diameter measured while driving in a car simulator under velocity of 80-120 km/h, daylight, linear trajectory and low traffic level. Data analysis was based on the method of fixation-aligned pupillary response averaging.

RESULTS: Noise curves were around baseline (zero) values while pupil dilation curves clearly stood out from noise magnitude, in all conditions for both groups. Greater pupil dilation peak during talking on the cell phone (handheld and hands-free conditions) while driving occurred only for the novice group.

CONCLUSION: Adaptation and application of the method of fixation-aligned pupillary response averaging to the car driving context succeed. Cognitive workload imposed by the dual task of talking on a cell phone increased pupil dilation for novice drivers, which may alter acquisition of visual information and impair driving behavior.