Perceptual organization of apparent motion in the Ternus display

A typical Ternus display has three sequentially presented frames, in which frame 1 consists of three motion tokens, frame 2 (blank) defines the inters timulus interval, and frame 3 has similar motion tokens with their relative positions shifted to the right. Interestingly what appears to be a seeming ly simple arrangement of stimuli can induce one of two distinct apparent-mo tion percepts in the observer. The first is an element-motion perception wh ere the left-end token is seen to jump over its two neighboring tokens (inn er tokens) to the right end of the display. The second is a group-motion pe rception where the entire display of the three tokens is seen to move to th e right. How does the visual system choose between these two apparent-motio n perceptions? It is hypothesized that the choice of motion perception is d etermined in part by the perceptual organization of the motion tokens. Spec ifically, a group-motion perception is experienced when a strong grouping t endency exists among the motion tokens belonging to the same frame. Convers ely, an element-motion perception is experienced when a strong grouping ten dency exists between the inner motion tokens in frames 1 and 3 (ie the two tokens that overlap in space between frames). We tested this hypothesis by varying the perceptual organization of the motion tokens. Both spatial (for m similarity, 3-D proximity, common surface/common region, and occlusion) a nd temporal (motion priming) factors of perceptual organization were tested . We found that the apparent-motion percept of the Ternus display can be pr edictably affected, in a manner consistent with the perceptual organization hypothesis.