Comparison between Figure Discrimination and Color Discrimination by Hue Differences of Multi-colored Regions with Saturation Distributions

Abstract

The visual system can segregate a figure from the background by grouping similar colors. Chromatic characteristics of figure segregation have not been fully investigated as compared with those of uniform color discrimination. In this study, we investigated differences in chromatic characteristics between figure segregation and color discrimination. The stimulus was a multi-colored texture composed of random shape pieces. It was divided into two regions, the test region and the background region. The chromaticities of the test and background regions distributed on isoluminant lines, which started at the origin in the DKL color space. These isoluminant lines varied in hue direction. The chromaticity distributions of the test and the background regions were the same in saturation. We measured hue difference thresholds between the test and background regions for figure segregation and for color discrimination. In threshold measurement for figure segregation, the observer judged whether two test region figures were identical. In the results, both thresholds of figure segregation and color discrimination for all color directions increased as the saturation distribution increased. These results suggest that figure segregation and color discrimination were not conducted performed by the cone-opponent mechanisms. Properties in hue difference for figure segregation and color discrimination thresholds were found different in the similar manner between observers. These hue property differences imply that there exist some factors effective in hue in a certain level from color discrimination to figure segregation.