Abstract
As the ways of studying the nature of consciousness, both crowding and binocular rivalry are commonly used to render visual stimuli invisible. Crowding is the interference of object identification in peripheral vision when an object is flanked by other objects, and binocular rivalry is alternating perception created by presenting two different objects separately to each eye. We investigated whether these two phenomena interacted with each other in orientation discrimination. The task in our experiments was to discriminate the orientation of the target. In Experiment 1, we measured the thresholds of orientation discrimination when the target underwent both binocular rivalry and crowding. Either flankers (surrounding the target to produce crowding) or a competing grating (presented to the same location of the target in the opposite eye to evoke rivalry) increased the thresholds. When both the flankers and the competing grating were present at the same time, the thresholds increased more than the sum of the two effects alone. In Experiment 2, we used flankers undergoing rivalry to examine the effect of rivalry on crowding. The crowding effect with flankers undergoing rivalry was closer to the effect of collinear flankers than that of orthogonal flankers. These results suggest that rivalry does not influence the effectiveness of flankers in crowding, and crowding may occur before or at the site of rivalry. In Experiment 3, we measured mean phase durations to examine the effect of crowding on binocular rivalry. When a collinear grating to flankers was visible, suppression from flankers changed the current percept. However, when an orthogonal grating to flankers was visible, suppression from flankers helped to maintain the current percept. In conclusion, our results suggest that crowding interacts with binocular rivalry and crowding occurs before or at the site of rivalry.
This research was supported by the Converging Research Center Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (2009-0093901).