The effects of age on the contributions of head and eye movements to scanning behavior at intersections.

The current study was aimed at evaluating the effects of age on the contributions of head and eye movements to scanning behavior at intersections. When approaching intersections, a wide area has to be scanned requiring large lateral head rotations as well as eye movements. Prior research suggests older drivers scan less extensively. However, due to the wide-ranging differences in methodologies and measures used in prior research, the extent to which age-related changes in eye or head movements contribute to these deficits is unclear. Eleven older (mean 67 years) and 18 younger (mean 27 years) current drivers drove in a simulator while their head and eye movements were tracked. Scans, analyzed for 15 four-way intersections in city drives, were split into two categories: eye-only (consisting only of eye movements) and head+eye (containing both head and eye movements). Older drivers made smaller head+eye scans than younger drivers (46.6° vs. 53°), as well as smaller eye-only scans (9.2° vs. 10.1°), resulting in overall smaller all- gaze scans. For head+eye scans, older drivers had both a smaller head and a smaller eye movement component. Older drivers made more eye-only scans than younger drivers (7 vs. 6) but fewer head+eye scans (2.1 vs. 2.7). This resulted in no age effects when considering all-gaze scans. Our results clarify the contributions of eye and head movements to age-related deficits in scanning at intersections, highlight the importance of analyzing both eye and head movements, and suggest the need for older driver training programs that emphasize the importance of making large scans before entering intersections.