Local and global segmentation of rotating shapes viewed through multiple slits.

Rotating outline squares and circles were viewed through a sunburst pattern of stationary radial slits. At slow rotation rates the (dotted) square was perceived globally as a single rotating shape, and at higher rates, as a set of independent local dots moving in and out radially. An eccentrically rotating circle was seen as a dotted circle; the dots comprising the circle actually moved in and out along straight radial paths, but observers could never see this. Instead, they saw the dots as running around the rim of the circle. The common motions were rejected, perhaps by subtracting the mean motion of all points from each point. Only relative motion could be seen, and absolute dot motions were not available to consciousness. Thus the visual motion system parsed patterns of absolute motion vectors into patterns of relative motion vectors.