Multistable perception

Multistable perceptual phenomena are a form of perceptual phenomena in which there are unpredictable sequences of spontaneous subjective changes. While usually associated with visual perception, such phenomena can be found for auditory and olfactory percepts.

Perceptual multistability can be evoked by visual patterns that are too ambiguous for the human visual system to recognise with one unique interpretation. Famous examples include the Necker cube, Schroeder staircase, structure from motion, monocular rivalry and binocular rivalry, but many more visually ambiguous patterns are known. Since most of these images lead to an alternation between two mutually exclusive perceptual states, they are sometimes also referred to as bistable perception.

Auditory and olfactory examples can occur when there are conflicting and so rivaling inputs into the two ears or two nostrils.

Transitions from one percept to its alternative are called perceptual reversals. They are spontaneous and 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 have been found to be slower for people with bipolar disorder.

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. Multistable perception was a common feature in the artwork of the Dutch lithographer M. C. Escher, who was strongly influenced by mathematical physicists such as Roger Penrose.

...
Wikipedia