Dissociating Eye Movements and Workload on Lateral Lane Position Variability

Recent research suggests that performing a secondary, non-visual task while driving may lead to a reduction in lateral vehicle movement. A plausible explanation for this counterintuitive pattern involves the joint findings that (1) increased cognitive load disrupts eye movements, and (2) eye movements often precipitate steering input. However, a partial dissociation of these factors by Cooper et al. (2009) found that increases in workload and eye movements (at a constant eccentricity) both reduce lateral lane variability. This follow-up study examines the contribution of eye movement eccentricity, under varying workload, on lateral lane position variability. Thirty-two participants drove nine, five minute scenarios in a fixed based driving simulator under varying eye movement and workload conditions. Consistent with previous finding, increased workload led to a decrease in lateral vehicle movement. Interestingly, an effect of visual eccentricity on eye movements was only observed in one of the driving measures. This research suggests that the impact of eye movements on lateral vehicle movement is much smaller than previously hypothesized and that impact of workload is much greater even after accounting for lateral shifts in eye movements.