Abstract
A stationary Gaussian envelope of a Gabor patch that contains a moving carrier is perceptually shifted in the direction of the motion, referred to as motion-induced position shift (MIPS). When such motion patches are arranged to comprise a diamond-shaped constellation with a physical aspect ratio of 1:1 and moved according to a particular deformation vector field, the MIPSs produced in these patches make the diamond as a whole appear to be distorted vertically or horizontally. Previously it has been reported that adaptation to such perceptually distorted diamonds consisting of many motion patches produces a figural aftereffect (FAE), suggesting that the process responsible for our shape perception about aspect ratio utilizes positional cues coming from motion processing. To clarify the contributing factors for the above phenomenon, here we investigated whether the FAE requires a specific constellation, motion patches, or a motion vector field. In an experiment, we removed the diamond constellation so that motion patches were randomly arranged in space, losing a diamond shape, whilst keeping the occurrence of MIPS and a deformation vector field to induce perceptually vertical or horizontal distortion. In another experiment, we removed both the diamond constellation and patchy configuration, whilst keeping only a random-dot pattern moved according to a deformation vector field. The results indicated that the constellation distorted by the MIPS produced in motion patches and the deformation vector field were needed for the FAE to occur. Our studies are the first to show relationships between a deformation vector field in motion processing and the shape processing about aspect ratio perception. We will discuss the effects of motion processing on shape processing, especially focusing on how position representation affected by motion processing is utilized in shape processing and how the computation based on a vector field in motion processing changes aspect ratio processing.