Multistable perception



Multistable perceptual phenomena are a rare form of visual perception, characterized by an unpredictable sequence of spontaneous subjective changes.

Classification
Perceptual multistability can be evoked by a large number of visual patterns that are too ambiguous for the visual system to settle down on a unique interpretation. Famous examples include the Necker cube, Structure from motion, Monocular rivalry and Binocular rivalry, but many more visually ambiguous patterns are known. Because most of these images lead to an alternation between two mutually exclusive perceptual states, they are sometimes also referred to as bistable perception.

Characterization
Transitions from one percept to its alternative are called perceptual reversals. They are spontaneous and stochastic events which cannot be eliminated by intentional efforts (although some control over the alternation process is learnable). Reversal rates vary drastically between stimuli and observers, and has been found to be slower for people with Bipolar Disorder ("sticky" interhemispheric switch in bipolar disorder).

Cultural history
Human interest in these phenomena can be traced back to antiquity. The fascination of multistable perception probably comes from the active nature of endogenous perceptual changes or from the dissociation of dynamic perception from constant sensory stimulation. In the 1980s, multistable visual patterns caught the attention of philosophers, psychologists, and neuroscientists.