Motion aftereffect
Encyclopedia
The motion after-effect is a visual illusion experienced after viewing a moving visual stimulus
for a time (seconds 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
adaptation
.
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.
Example movie which produces distortion illusion after one watches it and looks away.
coding a particular movement reduce their responses with time of exposure to a constantly moving stimulus; this is neural adaptation
. 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). 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 downwards movement reduces their baseline activity, tilting the balance in favor of upwards movement.
(approx. 350 B.C.) reported illusory movement after viewing constant movement, but 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 (1888).
Stimulation
Stimulation is the action of various agents on nerves, muscles, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity.The word...
for a time (seconds 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
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
adaptation
Neural adaptation
Neural adaptation or sensory adaptation is a change 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 one rests one's hand on a table, one immediately feels the table's surface on one's skin. Within a...
.
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.
Example movie which produces distortion illusion after one watches it and looks away.
Explanation
NeuronsNeuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
coding a particular movement reduce their responses with time of exposure to a constantly moving stimulus; this is neural adaptation
Neural adaptation
Neural adaptation or sensory adaptation is a change 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 one rests one's hand on a table, one immediately feels the table's surface on one's skin. Within a...
. 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). 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 downwards movement reduces their baseline activity, tilting the balance in favor of upwards movement.
History
AristotleAristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
(approx. 350 B.C.) reported illusory movement after viewing constant movement, but did not specify its direction. The first clear specification of the motion aftereffect was by Jan Evangelista Purkyně
Jan Evangelista Purkyne
Jan Evangelista Purkyně was a Czech anatomist and physiologist. He was one of the best known scientists of his time. His son was the painter Karel 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
Falls of Foyers
The Fall of Foyers is a waterfall on the River Foyers, which feeds Loch Ness, in Highland, Scotland, United Kingdom....
in Scotland. According to Verstraten (1996) the term waterfall illusion was coined by Thompson (1888).
External links
- "Neave Strobe" - an example of this effect (enable javascript to view).
- "Spiral aftereffect" - another example of this effect (requires Adobe FlashAdobe FlashAdobe Flash is a multimedia platform used to add animation, video, and interactivity to web pages. Flash is frequently used for advertisements, games and flash animations for broadcast...
).