Texture segregation based on two-dimensional relative phase differences in composite sine-wave grating patterns.

Experiments examined the visual processing of relative phase relations between differently oriented components of a textured pattern. The textures were a super position of three 1.3 c/deg sine-wave gratings rotated 60 deg relative to one another. Global orientation and relative phase were varied. Subjects rated the segregation of pairs of textures presented in a figure/ground configuration at 10 deg retinal eccentricity. Both orientation and phase differences were used in making ratings. It was not simply the difference in relative phase that mattered. The results also depended on the values of the relative two-dimensional (2-D) phases in figure and ground. Mirror-image texture pairs (which may have a large relative phase difference) segregated poorly compared to other pairs with similar phase differences. This suggests that the peripheral visual system does not completely encode 2-D relative phase. Secondary issues include spatial frequency effects, the relevance of figure/ground borders, and better performance in the lower visual field.