Multistable Perception

Multistable perception, also called bistable perception, is a perceptual phenomenon in which an observer experiences an unpredictable sequence of spontaneous subjective changes in how a single, unchanging stimulus is interpreted. The phenomenon is most commonly discussed in the context of vision and optical illusions, but it can also occur with auditory and olfactory percepts, not only visual ones. Classic visual examples of the phenomenon include the Necker cube and Schroeder stairs, both ambiguous figures whose actual image never changes but whose perceived interpretation spontaneously flips back and forth between two or more alternatives while the viewer looks at them.