Abstract
Research on optical flow has demonstrated its usefulness for the perception of heading (Warren, Morris, & Kalish, 1988; Warren, Mestre, Blackwell & Morris, 1991). In addition, studies have shown that landmarks are used in controlling steering (Andersen & Enriquez, 2006). The present study investigated age-related differences in the use of optical flow information and landmarks in steering control. Older and younger observers were presented with computer generated displays simulating vehicle motion through a random dot ground plane scene. The horizontal position of the observer was perturbed according a sum of three sinusoidal functions and observers were asked to steer the vehicle to null out the perturbation (compensatory tracking task). When the dots moved out of the observer's view they were recycled at the horizon while remaining their previous positions. In Experiment 1, the independent variables were dots density and the presence of landmark information which was depicted by color coding one of the dots on the ground plane. In Experiment 2, the number of landmarks was manipulated to assess the number of landmarks used to control steering. In Experiment 3, the reappearing positions of the landmarks were shifted horizontally by a certain amount when they were recycled. This was done to further test the use of landmark information in steering control. The results showed that younger observers had reduced steering error compared to older observers. Older observers were more dependent on optical flow information for steering control when there was less landmark information. With increased landmark information, both younger and older observers improved their driving performance. However, older observers had a high degree of error when there were 7 or 10 landmarks presented in the scene.
This work was supported by NIH AG13419-06 and NEI EY18334-01.