Abstract
A distribution of vertical disparity in the visual field contributes to stereoscopic depth perception. Vertical size disparity (VSD), one of the vertical disparity distribution patterns, causes slant-in-depth perception of a surface. When two groups of visual elements have different VSDs, their VSDs are pooled over large region in the visual field with linear weighting by the relative density of the elements. However, very little is known about other properties of VSD pooling. In this study, we investigated the effect of luminance contrast on VSD pooling and found that the perceived slant from the pooled VSD is highly dependent on the contrast difference between the element groups.
In the experiment 1, we used random-dot stereogram consisted of two groups of dots on a black background. The groups had the same density and were uniformly intermingled on a large screen. The groups had different VSDs, and the dot luminance in each group was complementarily manipulated. The result indicated that the VSDs were pooled across the two groups even when the luminance was greatly different. Furthermore, the perceived slant was highly dependent on the luminance difference.
In the experiment 2, we manipulated the luminance contrast of the dot groups relative to a gray background. The perceived slant was highly dependent on the contrast difference between the groups, not the luminance itself.
These results indicate that the process of extracting signals from vertical disparities is mediated by non-linear weighting of the luminance contrast in the image.