Preattentive equivalence of multicomponent Gabor textures in the central and peripheral visual field.

Similarity ratings were obtained to determine the minimum number of Gabor components that would produce a comparison texture that appeared preattentively similar to a 64-component standard texture. All textures were chosen to be both specifiable by a relatively small number of localized spectral components and sufficiently complex to approximate natural textures. The number of component orientations in the set of comparison textures was found to be a particularly important determinant of texture discrimination in that its effect on rated similarity was largely independent of the total number of components making up the texture. Textures were also presented at 0.75 degree and 20 degrees eccentricity, with the latter magnified by a factor of either 2 or 4. The overall similarity rating did not change with either magnification, whereas the critical number of orientations, defined as the number of orientations above which rated similarity was constant, did change for the higher magnification. The latter finding is consistent with the proposition that higher-order discriminations are mediated by higher cortical areas that integrate information across the visual field. Finally, the phase-bandwidth of a set of coherent textures was also varied in order to determine whether more explicit differences in the spatial structure of stimuli might affect rated similarity. In contrast to the results for component orientation, the ratings, obtained at 0.75 degree and 20 degrees, were different even when the phase-bandwidth stimuli were magnified by a factor of 4.