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Not to be confused with allusion. For other uses, see Illusion (disambiguation)
"Head on a Platter" exhibit at the Regional Science Centre, Bhopal

An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. Though illusions distort reality, they are generally shared by most people.[1] Illusions may occur with any of the human senses, but visual illusions (optical illusions), are the most well-known and understood. The emphasis on visual illusions occurs because vision often dominates the other senses. For example, individuals watching a ventriloquist will perceive the voice is coming from the dummy since they are able to see the dummy mouth the words.[2] Some illusions are based on general assumptions the brain makes during perception. These assumptions are made using organizational principles (e.g., Gestalt theory), an individual's capacity for depth perception and motion perception, and perceptual constancy. Other illusions occur because of biological sensory structures within the human body or conditions outside of the body within one’s physical environment.


Mimes are known for a repertoire of illusions that are created by physical means. The mime artist creates an illusion of acting upon or being acted upon by an unseen object. These illusions exploit the audience's assumptions about the physical world. Well-known examples include "walls", "climbing stairs", "leaning", "descending ladders", and "pulling and pushing".

Optical illusions[edit]

Main article: Optical illusion

An optical illusion is characterized by visually perceived images that are deceptive or misleading. Therefore, the information gathered by the eye is processed by the brain to give, on the face of it, a percept that does not tally with a physical measurement of the stimulus source. A conventional assumption is that there are physiological illusions that occur naturally and cognitive illusions that can be demonstrated by specific visual tricks that say something more basic about how human perceptual systems work. The human brain constructs a world inside our head based on what it samples from the surrounding environment. However, sometimes it tries to organise this information it thinks best while other times it fills in the gaps.[3][4] This way in which our brain works is the basis of an illusion.

Auditory illusions[edit]

Main article: Auditory illusion


Tactile illusions[edit]

Main article: Tactile illusion


Temporal illusions[edit]

Temporal illusions can occur in many ways.

Other senses[edit]





In an experiment with one patient, electrical stimulation at the left temporoparietal junction lead to an illusion of another person close to her.[12][13]

See also[edit]

Not related to senses (cognitive illusions)


  2. ^ McGurk, Hj.; MacDonald, J. (1976). "Hearing lips and seeing voices". Nature 264: 746–748. doi:10.1038/264746a0. 
  8. ^ Zampini M & Spence C (2004) "The role of auditory cues in modulating the perceived crispness and staleness of potato chips" Journal of Sensory Studies 19, 347-363.
  9. ^ Barnett-Cowan M (2010) "An illusion you can sink your teeth into: Haptic cues modulate the perceived freshness and crispness of pretzels" Perception 39, 1684-1686.
  12. ^ Arzy, S; Seeck, M; Ortigue, S; Spinelli, L; Blanke, O (2006). "Induction of an illusory shadow person". Nature 443: 287. doi:10.1038/443287a. 

External links[edit]