Abstract
The visual mechanism of grouping colors to segregate a figure from its background has not been fully understood. The visual system can detect a figure on a multi colored background by grouping some colored patches into a single figure. The colors of the figure patches should be distributed in a different region in color space from those of the background so that they appear similar. We investigated here what properties of color distributions of the figure and background influenced figure segregation by grouping colors.
The stimulus used in the present study consisted of small color patches with different colors. The color patch was separated from surrounding patches with a narrow gap. This texture stimulus was of the figure and the background area. The patch colors of these areas were selected from two sphere color distributions in the OSA uniform color space. These distribution spheres had the same radius, but their center positions were shifted. The observer judged whether two figures on a background were the same with 2AFC procedure. Thresholds of the distance between the distribution centers were measured.
We found that the thresholds were not equal for all directions of the shift between the figure and the background color distributions. The differences in thresholds were larger when the gap distance between the patches was smaller. Our results indicate that there seems to be a color grouping mechanism heterotropic in the color space with smaller gap distance, but becomes isotropic with larger gap distance.