PERIPHERAL AND FOVEAL SEGMENTATION OF ANGLE TEXTURES

Studies of the effects of retinal eccentricity on the visual segmentation of textures are presented. The textures used in these studies were composed of angle elements. These were presented tachistoscopically to college students in three different experiments. Results showed that there were different relationships between segmentation performance and eccentricity, depending on the width of the angles used in the background and target texture. One major difference was that peak performance was found in the fovea in some conditions, and in peripheral areas in other conditions. Performance in the fovea and the periphery seemed to be determined by qualitatively different features. It was assumed that an appropriate explanation is that the system-internal representation of a specific stimulus within the early visual system differs as a function of the retinal location at which it is projected. Thus, the critical features discriminating between target and background texture have to be sought in the system-internal representation of the stimulus instead of in the stimulus itself. The data show that a relatively exact system-internal representation of the stimulus is present in the fovea, where performance is determined by angle width. In the periphery, in contrast, angles seem to be represented as ''blobs,'' and performance is determined by the orientation of the blobs' main axes.