Figure 1.

Binocular rivalry paradigm. a, Experimental setup. Two images, each randomly selected from a bank of standard objects, were presented on the horizontal meridian of an LCD screen, surrounded by a black circle (radius: 4.95°) and a tinted square (width: 3.5°; red or green). A mirror stereoscope reflected the left and right sides of the screen to the participants' left and right eyes (respectively), so that each eye viewed a unique image. This presentation is known to induce binocular rivalry, in which the two incongruous monocular inputs “rival” for perceptual awareness, so that only one input dominates perceptual experience at any given instant. b, A sample sequence of binocular rivalry alternations. Throughout a run, participants were instructed to continuously report their perceived image (red, green, intermediate) through button press (right, left, up). The end of an episode of perceptual dominance was labeled a “transition.” Transitions were retrospectively divided into switches (e.g., R-Up-L) and reversions (e.g., L-Up-L).