Visual system responds to rotational and size-change components of complex proximal motion patterns.

Abstract

The qualitative and quantitative characteristics of rotation, contraction, and motion-in-depth motion aftereffects (MAEs) produced by rotating Archimedes spirals were compared for spirals differing in arm length (90°, 270°, and 720°). There were three test stimuli. The spokes and rings test stimuli were figures whose contours were orthogonal to the direction of motion of the MAEs produced by the rotational and radial components of the spiral’s motion, respectively. The floating disk test stimulus was used to test for a motion-in-depth MAE. In Experiment 1, naive subjects viewed the spirals for 30 sec and 3 min. The MAE components reported corresponded to the rotational and radial components of motion in the proximal stimulus. In Experiment 2, experienced subjects were used to measure decay time constants (DTCs) after 15 min of adaptation. The rotation MAE had a DTC that was shorter than the other two DTCs. Results support the hypothesis that the complex stimulus produced by rotating Archimedes spirals is resolved into rotational and radial components by structures in the visual system that are specifically sensitive to rotational and size-change relative motion patterns (Regan, 1986). They also support Hershenson’s (1982) suggestion that the spiral aftereffect is produced by the same perceptual structures that mediate the perception of rigid object motion in depth.