Texture Segregation in Chromatic Element-Arrangement Patterns
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We compare the perceived segregation of element-arrangement patterns1 which are composed of two types of squanes arranged in vertical stripes in the top and bottom regions and in a checkerboard in the middle region. The squares in a pattern are either equal in luminance and differing in hue or equal in hue and differing in luminance. Perceived segregation of squares differing in hue is not predicted by their rated similarity, but rather by the square-root of the sum of the squares of the differences in the outputs of the L-M and L+M-S opponent channels. Adaptation to the background luminance affects judgements of perceived segregation but does not affect judgments of perceived similarity. For a given background luminance, perceived segregation is a linear function of cone contrasts. Perceived hue similarity is instead a linear function of cone excitations across the background luminances. High and low luminance backgrounds decrease the perceived segregation of patterns differing in luminance. A high luminance achromatic background decreases the perceived segregation of patterns differing in hue but a low luminance achromatic background does not. The results indicate that the adaptation luminance affects the contribution of luminance differences between the two types of squares to perceived segregation but not the contribution of hue differences. For element-arrangement patterns composed of squares of equal luminance that differ in hue, perceived segregation is associated with differences in the perceived brightness of the hues. The results are consistent with the findings that the perceived segregation in element-arrangement patterns is primarily a function of the early visual mechanisms that encode pattern differences prior to the specification of the forms of the squares and their properties.
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