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.
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 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.
Real world examples
Photographs of craters, from either the moon or other planets including our own, can exhibit this phenomenon. Craters, in stereo imaging, such as our eyes, should appear to be pit-like structures. However in mono-vision, such as that of photographs, the elimination of our depth perception causes multistable perception to take over, and this can cause the craters to inverse their depth values and instead look like plateaus rather than pits. Sometimes rotating the image so that the photographic direction of the source of light matches a light source in the room can cause the correct perception to suddenly switch.
Multistable perception arises with the theater segments of Mystery Science Theater 3000, as due to the construction of the Crow T. Robot puppet, its head can appear to be facing towards the camera rather than towards the film being shown. This was addressed by the creators of the series, even likening Crow to a Necker Cube. 
- Optical illusion
- Experimental psychology
- Gestalt psychology
- Cognitive neuroscience
- M. C. Escher
- Salvador Dalí
- Op art
- The Spinning Dancer
- Alais, D; Blake, R., ed. (2005). Binocular Rivalry. MIT Press. ISBN 0-262-01212-X.
- Kruse, P.; Stadler, M. (1995). Multistable Cognitive Phenomena. Springer. ISBN 0-387-57082-9.
- Eagleman, D. (2001). "Visual Illusions and Neurobiology" (pdf). Nature Reviews Neuroscience 2 (12): 920–926. doi:10.1038/35104092. PMID 11733799.
- Deutsch, D. (1974). "An Auditory Illusion". Nature 251 (5473): 307–309. doi:10.1038/251307a0. PMID 4427654.
- Zhou, W.; Chen, D. (2009). "Binaral Rivalry Between the Nostrils and in the Cortex". Current Biology 19 (18): 1561–1565. doi:10.1016/j.cub.2009.07.052. PMC 2901510. PMID 19699095.
- Pettigrew, J. D.; Miller, S. M. (1998). "A 'sticky' interhemispheric switch in bipolar disorder?". Proceedings of the Royal Society B: Biological Sciences 265 (1411): 2141–2148. doi:10.1098/rspb.1998.0551. PMC 1689515. PMID 9872002.
- Miller, S. M.; Gynther, B. D.; Heslop, K. R.; Liu G. B.; Mitchell, P. B.; Ngo, T. T.; Pettigrew, J. D.; Geffen, L. B. (2003). "Slow Binocular Rivalry in Bipolar Disorder" (pdf). Psychological Medicine 33 (4): 683–692. doi:10.1017/S0033291703007475. PMID 12785470.
- Trace Beaulieu ... (1996). "The Mystery Science Theater 3000 Amazing Colossal Episode Guide". Bantam: 159. ISBN 0-553-37783-3.
- VisualFunHouse Optical Illusions Multistable perception Optical Illusions
- A collection of visually ambiguous patterns
- Miller, S. M.; Liu, G. B.; Ngo, T. T.; Hooper, G.; Riek, S.; Carson, R. G.; Pettigrew, J. D. (2000). "Interhemispheric Switching Mediates Perceptual Rivalry". Current Biology 10 (7): 383–392. doi:10.1016/S0960-9822(00)00416-4. PMID 10753744.
- Ambiguous figures Ambiguity of spatial perception (fr)