The Cheshire Cat effect.

Designing a binocular-rivalry exhibit for the Exploratorium resulted in the observation of some interesting phenomena. Under conditions of binocular rivalry, motion in the field of one eye can trigger suppression of the other visual field as a whole or in parts. This suppression sometimes occurs only in the area of motion. Subparts of a suppressed area often remain in the visual field. Conversely, moving an object into the suppressed area of a visual field can elicit dominance of that object alone, with the rest of the field remaining suppressed. The suppression of partial areas of the visual field of each eye can occur simultaneously.