Undergraduate viewers, in 2 experiments, judged heading from displays simulating locomotion through tree-filled environments, with gaze off to the side. They marked their heading with a computer-mouse-controlled probe at 3 different depths. When simulated eye or head rotation generally exceeded 0.5 deg/sec, there was reliable curvature in perceived paths towards the fixated object. This curvature, however, was slight even with rotation rates as great as 2.6 deg/sec. Best-fit paths to circular arcs had radii of 1.8 km or more. In a 3rd experiment, pedestrians walked with matched gaze to the side. Measured curvature in the direction of gaze corresponded to a circular radius of ~1.3 km. Thus, at a minimum, vision scientists need not be concerned about perceived path curvature in this situation; real path curvatures are about the same. However, presently, no claim can be made that the same mechanisms govern both results.
Abstract