MECHANISMS UNDERLYING SEGMENTATION OF COLORED TEXTURES

This paper examines the nature of the post-receptoral chromatic and ac hromatic mechanisms involved in a texture segmentation task Observers viewed a 64 x 64 square-element texture in which the chromaticity and brightness of each element was drawn from a one-dimensional Gaussian d istribution of values centered at a white point in color space. The or ientation in color space and variance of this distribution defined the noise in the stimulus. The mean chromaticity and/or brightness of a c entral 32 x 32 element area (the target) was shifted away from the whi te point along the same direction as the noise or along a different di rection. We measured target thresholds as a function of noise amplitud e. The steepness of this relationship defined the effectiveness of the noise. Within planes spanned by the achromatic axis and one of the tw o cardinal chromatic axes, we found selective effects of noise along e ach of the two cardinal axes. Within the purely chromatic (isoluminant ) plane, we found selective effects of noise along four lines-the two cardinal chromatic axes and two intermediate ones, We describe a simpl e model to account for our results. Copyright (C) 1996 Elsevier Scienc e Ltd.