Abstract
Previous research has found that the perceived distance between two points is affected by certain characteristics of the surface on which the points are located, such as discontinuities in the surface texture (e.g., Feria, Braunstein, & Andersen, Perception, in press; Sinai, Ooi, & He, Nature, 1998). The present study investigated whether perceived distance across a surface is affected by changes in the curvature of the surface. Observers viewed displays of a scene consisting of a textured ground surface that was translating horizontally and judged the distance across a horizontal interval marked by two poles. The surface was either entirely planar, or was planar except for a curved region within the horizontal interval. The curved region was either a convexity (hill) or a concavity (valley) and had one of two amplitudes. In Experiment 1, observers were presented with pairs of surfaces (planar vs. small and large convexity and small and large concavity, small vs. large convexity, and small vs. large concavity), with the same simulated distance interval in both surfaces in a pair. The two surfaces in a pair were presented sequentially for 8 sec each. The observers indicated which of the surface displays contained the larger interval. In Experiment 2, a third pole was added behind one of the horizontally separated poles and observers adjusted the separation between that pole and the pole in front of it to match the distance between the two horizontally separated poles. In both experiments, more distance was judged across planar regions than across regions containing changes in curvature. These results indicate that the perceived distance between two points depends on the curvature of the ground surface on which the points are located. The relationship of these results to the effects of texture discontinuities on judged distance will be discussed.
Supported by NIH Grant 1R01EY12437.