Assessment of driver's attentional resource allocation to visual, cognitive, and action processing by brain and eye signals

Driving a vehicle is comprised of multiple tasks (e.g., monitoring the environment around the vehicle, planning the trajectory, and controlling the vehicle), and requires the allocation of capacity-limited attentional resources to visual, cognitive, and action processing; otherwise, the quality of task performance will deteriorate, increasing the risk of near-accidents or crashes. The present study proposes that variations in the total amount as well as the individual amounts of attentional resources allocated to visual, cognitive, and action processing depending on the driving situations could be objectively estimated by the combined use of three physiological measures: (1) the duration of eye blinks during driving, (2) the size of eye-fixation-related potentials (EFRPs), i.e., event-related potentials (ERPs) that are time-locked to the offset of saccadic eye-movements during driving, and (3) the size of auditory-evoked potentials (AEPs), i.e., ERPs time-locked to the onset of task-unrelated auditory stimuli discretely presented during driving. We implemented these measures when participants (N = 16) drove a vehicle on a slalom course under four driving conditions defined by a combination of two levels of speed requirement (fast and slow) and two levels of path width (narrow and wide). The findings suggested that, (1) when driving at fast compared to slow speeds, the total amount of resources allocated to overall processing increased, which consisted of an increase in the amount of resources allocated to cognitive (and possibly action) processing and a decrease in the amount of resources allocated to visual processing, and (2) when driving on narrow compared to wide paths, the total amount of resources allocated to overall processing remained almost the same (due to complementary speed reduction), which consisted of an increase in the amount of resources allocated to visual processing, a decrease in the amount of resources allocated to cognitive processing, and almost the same amount of resources allocated to action processing. The driver's resource management strategies indicated by these results as well as the utility and limitations of the proposed method are discussed.