Aristotle's illusion

   The eponym Aristotle's illusion refers to the Greek philosopher Aristotle (384-322 BC), who appears to have been the first to describe the concomitant phenomenon in his books On dreams, Metaphysics,andProblems. The expression Aristotle's illusion is used to denote a tactile "illusion or " body schema illusion that occurs when a test person holds an object between the crossed index and middle fingers, in the absence of visual feedback, and tries to determine the number of objects thus held. Due to the perceptual system's inability to recognize the relative positions of the fingers, the single object tends to be interpreted as two objects. As the French philosopher Maurice Merleau-Ponty (1907-1961) wrote, "Aristotle's illusion is primarily a disturbance of the body image. What makes the synthesis of the two tactile perceptions in one single object impossible, is not so much that the position of the fingers is unaccustomed or statistically rare, it is that the right face of the middle finger and the left face of the index cannot combine in a joint exploration of the object." Aristotle's illusion is commonly classified as a "physiological illusion. Incidentally, not all the illusions described by Aristotle have been named after him. Two other illusions which he described have become known as the " Oppel-Kundt illusion and the river illusion (now generally referred to as the " waterfall illusion).

   References

   Aristotle (1984). On dreams.In: The complete works of Aristotle. The revised Oxford translation. Volume 1. Edited by Barnes, J. Princeton, NJ: Princeton University Press.

   Merleau-Ponty, M. (1962). Phenomenology of perception. Translated by Smith, C. London: Routledge.

   Johannsen, D.E. (1971). Early history of perceptual illusions. Journal of the History of the Behavioral Sciences, 7, 127-140.