Touch illusion
Encyclopedia
Tactile illusions are illusion
s that exploit the sense
of touch. Some touch illusions require active touch (e.g., movement of the fingers or hands), whereas others can be evoked passively (e.g., with external stimuli that press against the skin).
Illusion
An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people....
s that exploit the sense
Sense
Senses are physiological capacities of organisms that provide inputs for perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception...
of touch. Some touch illusions require active touch (e.g., movement of the fingers or hands), whereas others can be evoked passively (e.g., with external stimuli that press against the skin).
Examples
- One of the best known passive tactile illusions is the cutaneous rabbit illusionCutaneous rabbit illusionThe cutaneous rabbit illusion is a tactile illusion evoked by tapping two separate regions of the skin. Many experiments demonstrating the effect have been carried out on the forearm...
, in which a sequence of taps at two separated skin locations results in the perception that intervening skin regions were also tapped.
- If a person exposes their forearm and closes their eyes or turns their head in the opposite direction while a second person slowly traces a finger from the wrist upward to the crook of the elbow, many people are unable to say when the crease of their elbow is being touched.
- If one hand is immersed in cold water and the other in hot for a minute or so, and then both hands are placed in lukewarm water, the lukewarm water will feel hot to the hand previously immersed in cold water, and cold to the hand previously immersed in hot water.
- An example of an active touch illusion is the contingent after-effect. When the thumb and forefinger are slid repeatedly along the edge of a wedge, a rectangular block then handled in the same manner will feel deformed.
- Moving the crossed index and middle finger along an edge evokes the perception of two parallel edges. Similarly, if a person crosses their index and middle finger and then rolls a marble between the tips of the fingers, two marbles are perceived.
- If a person wears a baseball capBaseball capA baseball cap is a type of soft cap with a rounded stiff brim. The front of the cap typically contains designs or logos of sports teams ,...
for a long period of time and then takes it off, it may still be felt.
- If a person turns their tongue upside down, and runs their finger along the front, it will feel like the finger is moving in the opposite direction.
- If a person pushes outwards with their hands against something for a while, then stops, it will feel as if there is something stopping the person's hands from closing together. Similarly, if a person pulls outwards with their arms, for example pulling their pants outwards, then stops, it will feel as if something is keeping their hands from staying at their sides.
- If a person is lying on his/her stomach with arms stretched in front and another person raises his/her arms about 2 feet off the ground and holds them there for approximately one minute, with the person on the ground having his/her eyes closed and head hanging, then slowly lowers the arms to the ground, it will feel as if the arms are going below the level of the rest of the body.
- When touching paradoxical objects, you can feel a hole when actually you are touching a bump (Robles-De-La-Torre & Hayward 2001). These "illusory" objects can be used to create tactile "virtual objects" (see the MIT Technology Review article The Cutting Edge of Haptics).
- After exercising on a treadmill or walking on a moving sidewalk for extended periods, a person will often feel 'pulled forward' when they step off onto stationary ground.
- If two people join their opposite hands and one slides his index and thumb over two joined fingers he will feel the other finger like it was one of his.
External links
- Paradoxical objects. Touch illusions created with virtual reality technology.
- The Cutting Edge of Haptics Using touch illusions to create virtual objects with sharp borders. An article in MIT's Technology review by Duncan Graham-Rowe.