Manifestations of tactile disorders are disorders of the ability to detect internal sources of irritation, sensations of temperature, pain, pressure, humidity, the inaccuracy of distinguishing external signs of familiar objects and objects, illusory sensations and tactile hallucinations, imaginary perception of the body scheme.
One of the most ancient examples of tactile illusion known to all psychologists was presented by Aristotle (Aristotle’s “illusion”). If you cross two fingers and roll a pea or some small object between them, then the person will appear to be double.
The most successful and correct from the point of view of anatomy explanation for this phenomenon was given by Robertson. He explained this effect by the fact that when the object touches one by one with the index and middle finger, the points of contact are in different levels of space.
Therefore, an imaginary sensation (tactile illusion) arises that the point of touching the index finger is higher, although the finger is in reality lower, and vice versa – the point of touching the middle finger is lower, while in fact the finger is higher.
The sides of the fingers involved in this experiment are not located in a normal position in the space, and usually do not touch one object, so the consciousness perceives one object to which they are unaccustomed to touch, which is simultaneously in two places, that is, the consciousness of ” treats “it as two different subjects.
Not every distortion of the process of sensations and perceptions is considered by experts to be a sign of a mental disorder. Tactile illusions can arise in a healthy person under the influence of certain (“wrong”) conditions – with temporary functional disorders of the central nervous system (deep fatigue, absent-mindedness and against it is not the concentration of perception).
вра Physicians consider only the disorders of sensations and perceptions, which lead to a sharp and prolonged disruption in the identification of the surrounding and to the persistent formation of severe mental disorders, by pathological disturbances.
Psychologists distinguish a person with a tactile canal that is responsible for his bodily and tactile sensations – increasing or lowering the temperature and pressure, painful effects.
It is peculiar for a person to fix his unusual and unpleasant mental state on the grounds of changing his sensations in the physical sense. In other words, a person recognizes his fright (“registers”) in the “cold in the back” and “trembling in the knees,” excitement and delight determines by rapid heartbeat.
In general, manifestations of tactile illusions and hallucinations are expressed in the form of erroneous sensations of cold or heat (thermal illusions), touches to the body, tweaks (haptic illusions), the appearance of “goose bumps”, crawling of insects.
More recently, scientists from three academic institutions – the Massachusetts Institute of Technology, Harvard University and McGill University, have made an amazing discovery. They proved that it is quite possible to create tactile illusions similar to visual illusory effects.
According to one of the discoverers Christopher Moore, the brain (consciousness) interprets what is seen or tested to the touch, depending on the “context”, for a very simple reason – because the person subconsciously wants (tuned to this “wave”) and seeks to get an unexplored sensation.
He also explained the meaning of the work of a group of scientists, the desire to understand the general mechanisms of illusions (most of the imaginary perception is related to vision), and to make sure that in the field of touch can also artificially create an illusion.
To confirm their theory about the possibility of creating a tactile illusion by analogy with visual distortion, scientists conducted an experiment. They created a version of the tactile illusion according to the illusion of sight well known to all specialists – the illusion of a moving quartet.
Two large black points located in opposite corners of an imaginary geometric figure – a square, move at a high speed according to a certain scheme – “upper left + lower right corner – upper right + lower left”.
During this movement, the person begins to feel that the points are in horizontal or vertical motion (forward-backward, up-down). But, this is not the whole version of the illusion.
With prolonged observation of movement, a person discovers that moving up and down changes the movement from right to left and vice versa. Sometimes consciousness “offers” movement in a circle, in any direction. Scientists say that by effort of will you can change the direction of movement.
As this experiment confirms the possibility of creating an illusion – deceptive perception by the consciousness of a real action, it means that the same illusion can be created in the field of tactile sensations. Scientists used their device, originally created as a braille display (for people with damaged or weak eyesight) to conduct their experiment.
Each of the participants at the end of the experiment said that he felt with the fingers the same movements that he had previously seen on the screen, that is, the tactile perception turned out to be the same with the visual, including the created illusion.
Scientists from the center of intellectual machines of the Canadian University McGill (supervisor Vincent Hayward) created a special series of Braille displays that transmitted a visual image to the human skin receptors. This product served as Moore, and his colleagues an instrument for recreating tactile illusions.
Gradually complicating the conditions of the experiment by complicating the moving picture, scientists received an unexpected result – with increasing the movement of points and their number, the power of illusion increases. From what scientists have concluded that the brain somehow rearranges the received signals, and changes the perception of what is happening, the mechanism of perception is still unclear.
But, the main conclusion of the experimenters was that “games of consciousness” are possible for tactile perception, and, therefore, the mechanism of manifestation of illusions is common to all sense organs (and not just for visual perception), including for tactile sphere.
Another experiment based on the moving quartet was that all its participants moved their eyes at the request of scientists, repeating the perception of the movement of points on the Braille display (horizontally, vertically).
And it turned out that the imaginary movements under the fingers coincided with the actual movement of the eyes, and when the head of the experiment was tilted by 90 degrees, the direction of the movement of the points also changed in tactile illusion. This proves the presence of a direct connection between visual and tactile perceptions, as well as motor skills.
And more recently, another group of scientists has identified and proven that the sense of touch sharpens the eyesight, that is, the concept of “contact vision” actually exists, and the perception of the subject by the touch, helps him to see better.
The mechanism of tactile illusions is the same with visual illusory phenomena, which means that the human brain “independently” is able to process sensations of different senses, and combine it for themselves in the overall picture.