Abstract
Motion perception is one of the most fundamental aspects of visual perception and, as a result, the mechanisms underlying it have long been of interest. In the studies of motion perception, when moving dots are used as stimuli, their trajectories are, in most cases, set to be straight. In such cases, it is therefore logical to assume that they will be perceived as moving in straight lines. While the assumption seems to be valid in most cases, here we report a novel and robust visual illusion on motion trajectory, with which random dots moving in straight trajectories perceived wriggling. The illusion is observed when hundreds of dots move in straight trajectories and random directions without colliding with each other. In such a condition, the perceived trajectories are wriggling rather than straight. A total of twenty-one observers evaluated this "wriggling motion trajectory illusion" under various conditions. The illusion was most pronounced when there were a large number of dots moving at high speeds (Experiment 1). The illusion was independent of both the distance covered (Experiment 2) and the observer’s eye movements (Experiment 3). What causes the wriggling motion trajectory illusion? If hundreds of dots are randomly placed and all are moving in random directions along straight trajectories, it is very likely that many of them will collide somewhere along their paths. However, our stimuli do not contain any collision at all, and the observers did not see the collisions they expected. When the expectation is betrayed, one of the natural interpretations would be that the dots are avoiding each other by changing their paths. Such cognitive reasoning may explain the wriggling motion trajectory illusion. We propose that this "wriggling motion trajectory illusion" illustrates of how perception of motion can be modulated by high-level cognitive processing.
Meeting abstract presented at VSS 2012