Abstract
Tilt illusion is the phenomenon that the perceived orientation of center grating is altered by the presence of surround grating with a different orientation. The main purpose of this study is to test whether interocularly separated surrounds can induce tilt illusion during binocular rivalry. In both eyes, the stimulus was presented in three concentric areas; rivalrous orthogonal gratings were presented in the center area of each eye. In the adjacent repulsion condition, grating with 15° and grating with 75° were presented in the near-surround and in the far-surround, respectively. In the adjacent attraction condition, 75° and 15° were respectively presented. The task of participants was to respond whether the orientation of center was tilted toward clockwise or counterclockwise from horizontal or vertical. In the experiment 1, participants were asked to respond only when they perceived a whole stimulus without any piecemeal patches. As expected, a repulsive effect was found in the adjacent repulsion condition. Interestingly, however, in adjacent attraction condition a repulsive effect was found. These results can be interpreted at least two different ways; the influence from the visible far-surround in the same eye or from the invisible near-surround in the opposite eye. In experiment 2, it was examined whether the results of experiment 1 were induced from the invisible near-surround in the opposite eye. The same stimulus presented to left or right eye in experiment 1 was presented to both eyes. The repulsive effect from adjacent attraction condition was smaller than that in experiment 1 under binocular rivalry. The repulsive effect from adjacent repulsion condition was bigger than that in experiment 1 under binocular rivalry. These findings suggest that both repulsive and attractive effect could be induced from invisible rivalrous surroundings in the opposite eye and interocular grouping might be occurred without awareness.
Meeting abstract presented at VSS 2018