Object continuity in apparent motion and attention.

Recent theories of attention have emphasized the role of object-based representations in visual selection. One defining property of any object is spatiotemporal continuity. The present experiments show that the continuity property may underlie two seemingly unrelated perceptual phenomena: attentional capture by abrupt visual onset and the appearance of bistable apparent motion displays. In Experiment 1, observers carried out two visual tasks. In the first task, they reported the appearance of a bistable apparent-motion (or Ternus) display. Whether group or element motion was perceived depended on the duration of the blank interval between successive frames. In the second task, subjects engaged in visual search for a prespecified target, and one each trial one element was briefly flickered off and back on. The degree to which that element captured attention also depended on the duration of the temporal gap. The time course of the gap duration effect in the visual search task was very similar to that for the Ternus display. In Experiment 2, we ruled out the possibility that the presence of an abrupt offset caused the results of Experiment 1. It is argued that the apparent motion and attentional capture phenomena examined here may reflect the operation of the same underlying mechanism: in both cases, a sufficiently long temporal gap disrupts spatiotemporal continuity, thereby fundamentally changing the perceived organization of the display.