Abstract
Previous studies have found that observers used tau-dot to regulate braking (Yilmaz & Warren, 1995; Fajen, 2005). Braking performance was also affected by other sources of visual information, such as global optical flow and edge rate (Fajen, 2005). In the current study we examined age-related differences in the use of visual information in regulating braking. Twelve younger (mean age = 21.2) and twelve older observers (mean age = 71.6) participated in the study. On each trial, observers viewed computer generated 3-D scenes (visual angle = 106.4° × 73.9°) simulating driving on a roadway towards three stop signs at a constant speed. The roadway had either no texture or black-and-white checkerboard texture with various densities. During the first 10 seconds, the observers did not have control over the brake. Ten seconds later, observers heard a warning tone indicating the control input was allowed. Their task was to apply smooth and continuous braking and stop as close as possible to the stop signs. The initial time-to-contact (3s, 3.5s, or 4.0s), initial distance from the stop signs (40m, 45m, or 50m), and the texture density on the ground (no texture, 32×16, 32×32, or 32×64) were manipulated. The texture density was blocked and counterbalanced across observers in each age group. The mean stop distance relative to the stop signs, the standard deviation of stop distance, crash rate and distribution of tau-dot were collected. We found that older observers had larger mean stop distances and lower crash rates than younger observers. In addition, older observers, as compared to younger observers, tended to regulate tau-dot more frequently at values larger than -0.5 and less frequently at values smaller than -0.5. These results, taken together, suggest that older observers may use a more conservative strategy to control braking in order to avoid collisions.
Meeting abstract presented at VSS 2013