Attentional modulation in perception of visual motion events

Identical visual targets moving across each other with equal and constant s peed can be perceived either to bounce off or to stream through each other. This bistable motion perception has been studied mostly in the context of motion integration. Since the perception of most ambiguous motion is affect ed by attention, there is the possibility of attentional modulation occurri ng in this case as well. We investigated whether distraction of attention f rom the moving targets would alter the relative frequency of each percept. During the observation of the streaming/bouncing motion event in the periph eral visual field, visual attention was disrupted by an abrupt presentation of a visual distracter at various timings and locations (experiment 1; exo genous distraction of attention) or by the demand of an additional discrimi nation task (experiments 2 and 3; endogenous distraction of attention). Bot h types of distractions of attention increased the frequency of the bouncin g percept and decreased that of the streaming percept. These results sugges t that attention may facilitate the perception of object motion as continui ng in the same direction as in the past.