ILLUSORY MOTION OF TEXTURE BOUNDARIES

We have measured the perceived direction of motion of rigid patterns containing texture boundaries at various orientations. Texture boundaries are defined here as the locus of 180-degrees phase shifts in a square-wave grating. When these patterns are moved parallel to the orientation of the grating, the perceived direction of motion in foveal viewing differs by as much as 45-degrees from the true direction of rigid motion as defined by the intersection of constraints (IOC) construction. At 8.0-degrees in the periphery the perceived direction was closer to the true direction of rigid motion. Thus, the peripheral visual system analyzes motion of these stimuli more accurately than does the fovea. These results are consistent with a current model of motion analysis that combines responses of Fourier and non-Fourier motion pathways using a vector sum operation.