Vertical anisotropy in stream/bounce perception of refracted motion trajectory

[摘要] When two identical objects moving toward each other coincide at the center and then pass through, observer perceives either of two motion events: streaming or bouncing (stream/bounce perception). In this study, we examined whether motion direction and trajectory refraction at the coincidence affect the stream/bounce perception. In Experiment 1, two identical black circles moved downward from the upper visual field (downward condition) or upward from the lower visual field (upward condition) at an angle of 45°. They coincided at the center of the display, and then their motion trajectory refracted up or down in the range of 0° to 15°. The velocity of the moving object was 6.21°/s. The results showed that a bouncing rate was significantly higher in the upward condition than in the downward condition, and significantly higher in the up 12° and 15° refraction conditions than in the 0° (i.e., no refraction) condition. In Experiment 2, we investigated the effect of the stimulus velocity on this phenomenon by manipulating the velocity to 2.07°/s (slow condition) or 10.35°/s (fast condition). The results indicated that the fast condition elicited a significantly higher bouncing rate than the slow condition although the effects of the direction and refraction on stream/bounce perception were not varied by the velocity of moving objects. In Experiment 3, we manipulated the duration of post-coincidence motion within the range of 150 ms to 600 ms. The results again showed the similar effect regardless of the post-coincidence duration, indicating that relatively short trailing motion is sufficient for this phenomenon. These results suggest that the mechanisms to detect motion information of vertical direction, refraction after coincidence, and velocity of moving objects underlie the stream/bounce perception maybe independently.

[学科分类] 眼科学