Where does our "I" end and the world around us begin? Why do we feel that our body belongs to us and we are able to control it? Can a foreign object be mistaken for a part of yourself? For those who find the answers to these questions simple and obvious, we will try to offer food for thought.
The sense of self is the result of a very complex interaction between the brain and the human nervous system and depends on the "input" supplied by the senses. If the brain or nervous system begins to malfunction, amazing, though not joyful things happen to our personality. For example, damage to the parietal lobe can result in a disorder called somatoparaphrenia. In this case, the patient ceases to feel his left arm or left leg as part of himself. He may even feel that someone else is controlling his own limbs. Another disease - unilateral spatial agnosia - leads to the fact that the patient simply ignores half of his body, as if it simply does not exist. For example, a woman applying makeup will apply powder, eye shadow or mascara only on one half of her face,leaving the other completely intact. In another case, a person suffering from a similar disease will eat exactly half of the dish from his plate, being in complete confidence that everything has been eaten. If the plate is turned 90 °, the patient as if nothing had happened eats up the second half of the porridge or salad.
Rubber hand
However, games with the minds of completely healthy people can also lead to unexpected results. There is an amazing experiment carried out by a group of scientists from the Department of Neuropsychology at the Carolingian Institute (Stockholm), led by Dr. Henrik Ersson. The experiment demonstrates the so-called "rubber hand illusion". The subject sits down and places his palm on the table surface. The hand is fenced off by a small screen, so that the participant of the experiment does not see it, however, a rubber dummy of a human hand is laid out directly in front of him on the same table. Now a member of the research team takes the brushes in his hands and begins to simultaneously stroke the subject's hand and the rubber dummy in the same places. A small miracle happens: after a while, visual information "clogs" the natural feeling of owning your own hand. The participant in the experiment begins to feel that the sensation of stroking with a brush comes from a piece of rubber.
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In other words, a person is able not only to “believe” that a part of the body does not belong to him, but also to feel completely “his own” a foreign object. The illusion is born in the so-called premotor region of the cerebral cortex, where neurons are located that receive both tactile and visual information and integrate data from both sources. It is this part of our “gray matter” that is largely responsible for the feeling of having our own body, drawing the line between “I” and “not I”. And now, as the studies of Swedish scientists have shown, in the matter of deceiving your own brain, you can go much further and not only recognize the rubber hand as "your", but also … feel yourself outside your own body. This is clearly demonstrated by the experiments of Henrik Hersson and his colleague Valeria Petkova.
First person
One of the main factors that allow us to feel the possession of our own body is the position of the eyes fixed in relation to the head, torso and limbs, that is, what we call "first-person vision." Examining ourselves, we always find all parts of our body oriented in a known way relative to each other. If, with the help of rather simple tricks and adaptations, change the "picture", the subject may have an illusion not only of being in another point of space, different from the real one, but also of moving his "I". In the course of the experiments, their participants felt themselves in the body of another person and even met with the "real self" face to face, shaking hands with him. All this time, the illusion persisted.
One of the simplest experiments, during which the illusion of movement into another body was noted, was carried out using a dummy. A helmet was put on the head of a mannequin standing upright, to which two electronic video cameras were attached. The body of a mannequin turned out to be in their field of vision - this is how we see our body from the first person, slightly tilting our head. In this position, with his head bowed forward, the subject stood opposite the dummy. He was wearing video glasses, on each of the screens of which a "picture" from video cameras on the mannequin's helmet was fed. It turned out that the participant in the experiment, looking at his own body, saw the body of a mannequin wearing glasses.
Next, a laboratory employee took two sticks and began to perform synchronous movements, lightly stroking the lower abdomen of both the subject and the dummy. For control and comparison, in some experiments, the stroking series were out of sync. After the end of the experiment, the subjects were asked to fill out a questionnaire in which they had to rate each of the probable sensations on a seven-point scale. As it was found out, illusions began to arise with synchronous stroking, and with asynchronous stroking they disappeared completely or appeared insignificantly. The most powerful sensations were the following: the participants in the experiment felt a touch to the body of the dummy; they also felt that the mannequin was their own body. Some of the subjects felt that their bodies had become plastic or that they had two bodies.
Fear lives in the skin
In another experiment, it was decided to use not only the subjective feelings of the subjects, but also objective indicators associated with changes in the electrochemical properties of the skin to confirm the "relocation" to another body. It is a measure of the skin conductance response that changes when a person experiences fear or danger. The beginning of the experiment completely coincided with the previous one, but after a series of synchronous strokes, the subject saw in his video glasses how a knife appeared next to the mannequin's belly, which cuts the "skin". For control and comparison, in some cases, the initial strokes were out of sync. In other experiments of the series, the dummy's stomach was “threatened” by a metal object similar in size, but not so formidable - a tablespoon. As a result, the greatest increase in the index of the skin conductance response in the subject was noted precisely when, after a series of synchronous stroking, the dummy received an incision with a knife. But even with asynchronous strokes, the knife still excelled over the spoon, which clearly less frightened the subject, who thought that he had become a dummy.
And in fact, is it so fundamentally important for the appearance of an illusion that the subject contemplates a model of the human body through his video glasses? Yes, the habit of seeing "from the first person" is the body that plays a key role in the effect. Special experiments, in which the dummy was replaced by a rectangular object that did not have anthropomorphic outlines, showed that the illusion of a feeling of belonging to a foreign object usually does not arise in this case.
However, oddly enough, gender plays almost no role in the illusion. In the experiments of Swedish researchers, a mannequin was used that uniquely reproduces the features of a male body. Moreover, both women and men were among the subjects. When the dummy's abdomen was threatened with a knife, the skin conduction response showed almost the same performance for both sexes. So for the illusion of transmigration to someone else's body, it is not required that it be similar to yours. It is enough that it is human.
Deceptive handshake
The topic of the exchange of bodies between two “I” formed the basis of the plots of many films and science fiction novels, but it is rather difficult to imagine such a thing in reality. It is much easier to make a person believe at least for a while that this is possible, and not in a cinema, but in a scientific laboratory.
The experiment with "body exchange" was organized as follows. A block of two video cameras was installed on the experimenter's head, which captured reality as the scientist's eyes saw it. Exactly on the contrary, in the field of view of the cameras, there was a subject wearing video glasses. As you might guess, the first-person image was broadcast on the video glasses, the way the experimenter's eyes perceived it. In this case, the participant in the experiment saw himself in glasses from about head to knees. The subject was asked to extend his right hand forward and shake the experimenter's hand. Then the experimenter and the subject had to squeeze and unclench their hands several times for two minutes. At first, the shakes were carried out simultaneously, and then asynchronously.
Subsequent interviews with the subject showed that in the course of the experiment a strong illusion arose of transmigration into a foreign body. The subject began to perceive the experimenter's hand as his own, since he saw his own body behind it. Moreover, it seems that the situation was that the tactile sensations that arose during the handshake went to the subject's brain precisely from the experimenter's hand, and not from his own, visible hand in front of him.
It was decided to complicate the experience with the introduction of an additional, "threatening" factor. At the moment of handshaking, the laboratory assistant held a knife along the wrist of the experimenter, then the subject. Of course, the skin was protected by tapes of a dense plaster, so there were no traumatic consequences of contact with cold weapons in reality. However, when measuring the conductance reaction of the subject's skin, it turned out that this indicator was noticeably higher then, the knife “threatened” the experimenter's wrist. The alien hand clearly seemed to the brain "closer to the body."
World of illusion
An illusion in psychology is called an incorrect, distorted interpretation of the signals from the senses by the brain. Illusion should not be confused with hallucination, since hallucination can occur in the absence of any effect on the receptors and is a consequence of painful changes in consciousness. Illusions, on the other hand, can be felt by completely healthy people.
We are familiar with optical illusions since childhood: who of us has not looked at static drawings that suddenly begin to move, dark specks at the intersection of absolutely white lines separating black squares from each other, or equal lengths in which the eye does not want to recognize equality. Auditory and tactile illusions are much less known, although some of them exhibit rather unusual properties of the brain-nervous system ligament.
The illusion of two balls was discovered by Aristotle. If you cross two fingers, index and middle, and roll a small glass ball with the tips of these fingers, while closing your eyes, it will seem that there are two balls. Roughly the same thing happens if one of the crossed fingers touch the tip of the nose, and the other - its side. If you choose the right position of the fingers, while also closing the eyes, then there will be a feeling of two noses.
Another interesting tactile illusion is associated with the nerve receptors in the skin of the wrist and elbow. If you consistently conduct a series of light tapping, first in the wrist area, and then in the elbow area, then without any physical impact, alternating jolts will be felt in the elbow area, then in the wrist area, as if someone is jumping back and forth. This illusion is often called the rabbit illusion.
Due to the fact that the density of receptors that respond to pressure in different parts of the body is different, an interesting converging compass effect occurs. If the subject, who closed his eyes, slightly tingles the skin on the outside of the hand with the divorced legs of the compass, and then, slowly bringing them together, repeat the injection, then at a certain distance between them the subject will cease to feel the touch of two legs and will feel only one injection.
Temperature receptors slightly trick the brain when we put one hand, taken out of a basin of hot water, and the other hand, taken from a basin of ice-cold water, into a third basin - with warm water. In this case, warm water will seem hot to one hand, and cool to the other. The mechanisms of tactile illusions are very diverse, but memory often plays a significant role in their occurrence.
Why, when touching the nose or the glass ball with crossed fingers, a person feels two objects instead of one? Yes, because in this way we bring together receptors, which in ordinary life almost never touch the same object. As a result, the object is bifurcated. In the decision-making process, to the information coming directly from the receptors, the brain adds some primary knowledge acquired during life. In most cases, this leads to the fact that decisions are made more accurately and faster, but sometimes this can be used in order to mislead the "gray matter".
The same mechanism works in the illusion of body exchange, which Henrik Ersson and Valeria Petkova were able to reproduce. Indeed, for the correct orientation of one's own body in space and for the feeling of belonging to one's own “I” of the body and limbs, the leading role is played by the view of oneself “from the first person”. Finding a way to substitute this view, the researchers destroyed the seemingly unbreakable connection between the body and individual consciousness.
It is important to note that the “first-person” look at oneself from the outside is something completely different from recognizing oneself in a mirror, on a screen or in a photograph. The thing is that life experience tells us that the “I” in the mirror is not “I”, that is, we are dealing with a view from the outside, “from the third person”.
For robots and theologians
Swedish researchers are interested in more than just playing with the human mind. In their opinion, these experiments will be of great importance for science, medicine, and industry. For example, data obtained from "body exchange" can help to better understand the nature of somatopsychic disorders, such as those mentioned at the beginning of this article, as well as identity problems in social psychology.
The experiments of the Swedes also have direct access to the problems associated with the design of remotely controlled robots and virtual reality systems, in which a person often controls his electronic alter ego in the first person.
And finally, it cannot be ruled out that the reports of neuropsychologists from Stockholm on how to make a person feel like a mannequin with the help of a simple device will become the starting point of a debate of an ideological, and maybe even a religious nature. Theologians have long argued about what connects the soul and body, and representatives of European schools of irrationalist philosophy have repeatedly tried to answer in their writings the question of what separates the "I" from the surrounding world, where is the thin border between "to be" and "to have" … Not that the answers to the questions of theologians and philosophers have finally been found, but it might be worth speculating on this topic again, taking into account the data of modern science.
Oleg Makarov
