Timing and Apparent Motion Path Choice With Human Body Photographs

In demonstrations of apparent motion, observers typically report seeing motion along the shortest possible path between two sequentially presented objects. Recent work has demonstrated that violations of this shortest path rule occur with realistic photographs of a human body displayed for sufficiently long temporal intervals when a longer path is more anatomically plausible than the shortest path. The current set of experiments investigated the mechanisms by which information about biomechanical motion constrains apparent motion perception. In Experiment I, we demonstrated, first, that the availability of extra processing time does not simply—in and of itself—result in the perception of longer paths of apparent motion. Second, we rejected the hypothesis that the perception of biomechanically correct paths of apparent motion depends on biologically appropriate velocities. In Experiment 2, we discovered that the longer the motion path required to satisfy the biomechanical movement limitations of the stimulus, the longer the time needed to construct and therefore perceive that path. These findings together suggest that additional processing time is necessary, but not sufficient, for interpolations of longer paths.