Abstract
Objects in a visual scene are not usually isolated and their surroundings may alter their perceived attributes. The speed of a moving background, for instance, can affect the perceived shape of an object moving in front of the background (Zhong & Braunstein, 2004). The present study investigated the effect of the spatial frequency content of a stationary background on the perceived shape of a moving object. The background was a frontally oriented horizontal or vertical sinusoidal grating with a spatial frequency of 0.6, 1.2 or 3.5 cycles/degree. A horizontally or vertically oriented cylinder rotated in front of the background. The texture pattern on the cylinder was also a sinusoidal grating with one of these three spatial frequencies. The observer's task was to adjust the length of a line presented on a separate monitor to match the perceived distance between the most convex part of the cylinder and the plane of the background. The perceived width of the cylinder was estimated in separate blocks of trials. We found a significant effect of the spatial frequency of the background on the perceived depth of the cylinder, with judged depth increasing with a decrease in spatial frequency. Judged width of the object did not vary significantly with the spatial frequency of the background. An increase in the spatial frequency of the texture grating on the cylinder resulted in an increase in judged depth and width, although this effect was less consistent across observers than the effect of the background. These effects may be due to changes in the perceived distance of the cylinder and background, associated with the spatial frequencies of the textures and the resulting variations in edge rate as the cylinder rotates.
Supported by NIH Grants EY-12437 and TW-05753.