Blinking and driving: the influence of saccades and cognitive workload.

PURPOSE The aim of this study was to investigate the joint influence of cognitive demands and large amplitude saccades on spontaneous blink rate. MATERIALS AND METHODS Twenty healthy volunteers were enrolled in the study and instructed to follow a 60-minute real-life driving circuit while a video camera recorded ocular movements and blinking. Five different complexity levels were predefined in terms of driving difficulty and traffic intensity, that is, cognitive workload. Five one-minute segments were selected for each complexity level in each driving trial, whereupon spontaneous blink rate and horizontal saccades were monitored. Saccades were classified according to their amplitude and blink-saccade pairs were recorded. RESULTS Albeit showing a high inter-subject variability, spontaneous blink rate and saccades were consistent within the same complexity level. At different complexity levels, no statistically significant difference in spontaneous blink rate was encountered, with an average of 20.3 ± 1.6 blinks/minute (mean ± SD). The number of large amplitude gaze shifts increased with the level of complexity (F = 15.403; p < 0.001). An average of 87.5% of large amplitude saccades were accompanied by a blink, and this percentage was similar for all complexity levels, that is, the number of blink-saccade pairs increased at higher complexity levels (F = 20.597; p < 0.001). CONCLUSIONS In a complex, dynamic visual setting, spontaneous blinking accompanying large amplitude saccades may help in counteracting the reduction in blink rate associated with high cognitive demands.