The motion aftereffect (MAE) is a

visual illusion In visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual perception, percept that arguably appears to differ from reality. Illusions come in a wide varie ...

experienced after viewing a moving visual stimulus for a time (tens of milliseconds to minutes) with stationary eyes, and then fixating a stationary stimulus. The stationary stimulus appears to move in the opposite direction to the original (physically moving) stimulus. The motion aftereffect is believed to be the result of

motion In physics, motion is when an object changes its position with respect to a reference point in a given time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed, and frame of reference to an o ...

adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the p ...

. For example, if one looks at a waterfall for about a minute and then looks at the stationary rocks at the side of the waterfall, these rocks appear to be moving upwards slightly. The illusory upwards movement is the motion aftereffect. This particular motion aftereffect is also known as the ''waterfall illusion''. Another example can be seen when one looks at the center of a rotating spiral for several seconds. The spiral can exhibit outward or inward motion. When one then looks at any stationary pattern, it appears to be moving in the opposite direction. This form of the motion aftereffect is known as the ''spiral aftereffect''.

Explanation

Neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

s coding a particular movement reduce their responses with time of exposure to a constantly moving stimulus; this is

neural adaptation Neural adaptation or sensory adaptation is a gradual decrease over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if a hand is rested on a table, the t ...

. Neural adaptation also reduces the spontaneous, baseline activity of these same neurons when responding to a stationary stimulus (see, for example, Barlow & Hill, 1963; Srinivasan & Dvorak, 1979; Glasser, Tsui, Pack, & Tadin, 2011). One theory is that perception of stationary objects—for example, rocks beside a waterfall—is coded as the balance among the baseline responses of neurons coding all possible directions of motion. Neural adaptation of neurons stimulated by downward movement reduces their baseline activity, tilting the balance in favor of upward movement.

History

Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...

(approx. 350 B.C.) reported illusory movement after viewing constant movement, but he did not specify its direction. The first clear specification of the motion aftereffect was by Jan Evangelista Purkyně (1820), who observed it after looking at a cavalry parade. Robert Addams (1834) reported the waterfall illusion after observing it at the Falls of Foyers in Scotland. According to Verstraten (1996), the term waterfall illusion was coined by Thompson (1880). According to Wade, Thompson, and Morgan, (2014), the most comprehensive single article on the phenomenon is by Gustav Adolf Wohlgemuth (1911).

References

Sources

*Addams, R. (1834). An account of a peculiar optical phenomenon seen after having looked at a moving body. ''London and Edinburgh Philosophical Magazine and Journal of Science, 5,'' 373–374 *Aristotle (approx. 350 B.C.) '' Parva Naturalia.'' *Barlow, H.B., & Hill, R.M. (1963). Evidence for a physiological explanation of the waterfall illusion. ''Nature, 200,'' 1345-1347. *Glasser, D. M., Tsui, J. M., Pack, C. C., & Tadin, D. (2011). Perceptual and neural consequences of rapid motion adaptation. ''PNAS Plus, 108''(45), E1080–E1088. *Petersen, S. E., Baker, J. F., & Allman, J. M. (1985). Direction-specific adaptation in area MT of the owl monkey, ''Brain Research, 346'', 146-150. *Purkinje, J. E. (1820) Beiträge zur näheren Kenntniss des Schwindels aus heautognostischen Daten. ''Medicinische Jahrbücher des kaiserlich-königlichen österreichischen Staates, 6,'' 79–125. *Srinivasan, M. V., & Dvorak, D. R. (1979). The waterfall illusion in an insect visual system. ''Vision Research, 19'', 1435-1437. *Thompson, P. (1880). Optical illusions of motion. ''Brain, 3,'' 289-298. *Tootell, R. B., Reppas, J. B., Dale, A. M., Look, R. B., Sereno, M. I., Malach, R., Brady, T. J., & Rosen, B. R. (1995), ''Visual motion aftereffect in human cortical area MT revealed by functional magnetic resonance imaging'', Nature, 375", 139-141. *Verstraten, F. A. J. (1996). On the ancient history of the direction of the motion aftereffect. ''Perception, 25,'' 1177-1188. *Wade, N. J., Thompson, P., & Morgan, M. (2014). The after-effect of Adolf Wohlgemuth’s seen motion. ''Perception, 43'', 229-234. doi: 10.1068/p4304ed *Wohlgemuth, A. (1911). On the after-effect of seen movement. ''British Journal of Psychology Monograph Supplement'', 1-117.

Bibliography

*Mather, G., Verstraten, F., & Anstis, S. (1998). ''The motion aftereffect: A modern perspective.'' Cambridge, Mass: MIT Press

External links