Effect of travel speed on visual control of steering toward a target

Abstract

It has been suggested that travel speed influences the use of visual strategies for the control of self-motion. Here we systematically examined the effect of travel speed on the control of steering toward a target. The display (113°H×89°V) simulated a participant traveling at 2m/s, 8m/s, or 15m/s over a textured ground plane. Participants used a joystick to control the curvature of their travelling path to steer toward a target. Two viewing conditions were tested: in the target fixation condition, the participant's virtual gaze direction was fixed on the target which was placed 10° away from the center of the screen. The target egocentric direction was fixed during steering and was thus unavailable for steering control. In the heading fixation condition, the participant's virtual gaze direction was aligned with heading which was displaced 10° away from the center of the screen. The target egocentric direction changed during steering and was thus available for steering control. Across five participants, mean last second heading error of 10-s steering was similar for the two viewing conditions and decreased significantly from 4.7°±1.5° (mean±SE) to 2.6°±1.0° and 1.7°±0.7° as travel speed increased from 2m/s to 8m/s and 15m/s, respectively. The steering delay was significantly lower at all speeds when target egocentric direction was available for steering. As travel speed increased, observers showed a significant increase in the steering delay when target egocentric cue was available (177±48ms, 210±57ms, and 230±64ms for the three speeds, respectively) but a significant decrease in the steering delay when this cue was unavailable (627±38ms, 557±15ms, and 540±20ms for the three speeds, respectively). We conclude that while high-speed travel does not affect the use of visual strategies for the control of self-motion, people are more accurate and efficient in using optic flow for steering control when travel speed increases.