Figure 1. Illustration of the stimuli and raw data.

(A) The apparent motion (AM) stimulus was created by presenting a red/green grating on alternate frames to a luminance-defined yellow grating, with gratings displaced by a quarter of a cycle in each frame (see Method Section). When viewed through red/green glasses, observers experience binocular rivalry between the red, rightward and green, leftward apparent motions. (B) The drifting (DM) and stationary (ST) gratings were matched with the apparent motion gratings for mean luminance and spatial frequency. During monocular (M) presentation, stimuli were exogenously switched upon each cue, so that one eye received a drifting grating and the other a blank field. (C) This segment of raw data illustrates voluntary control over binocular rivalry between the apparent motion gratings. The solid red and green bars represent auditory commands to switch to the red, leftward and green, rightward stimuli respectively. The red and green shadings illustrate subjective reports of leftward and rightward perception and the black trace illustrates corresponding switches in the direction of optokinetic nystagmus (OKN), our objective measure of perceptual state.