Abstract
Visual systems of humans and animals seem to extract critical information for object perception from the changing visual stimulation produced by object and observer motion. Although objects in ordinary scenes are often partially occluded, observers routinely perceive the shape of objects despite the occlusion and motion. This ability depends on interpolation processes that connect fragments across gaps in space and time to represent dynamically-occluded objects. Palmer, Kellman, and Shipley (2006, JEP:G) proposed that spatiotemporal interpolation depends on a Dynamic Visual Icon (DVI) which represents and positionally updates previously visible fragments. Little research, however, has explored the range of motions that support interpolation or the ecological validity of transformations that may be important to object interpolation in ordinary environments. In the present study, the effect of velocity gradients on interpolation of objects expanding or contracting behind occluding surface was examined. Six participants observed the shapes of interpolated objects through multiple apertures and made two-alternative forced choice of objects. Three conditions of velocity gradients were compared using correct response rate as a measure of object interpolation: (1) acceleration condition where local speeds of visual edges increased linearly towards periphery, (2) negative-acceleration condition where speeds of edges decreased linearly towards periphery, and (3) constant-speed condition where local speeds were held constant. The results showed that effects of velocity gradients were significant, and that observers perceived interpolated objects with higher probability in acceleration condition than in negative-acceleration or in constant-speed condition. These results suggest that direction and velocity gradients of moving edges which may represent approaching and receding objects have critical effects on visual interpolation of moving objects.