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Scientists who study the brain have managed to fool some people into believing that they were inside the body of another person or on a plastic mannequin.
The out-of-body experience - surprisingly easy to induce - will help researchers understand how the human brain builds a physical sense of itself. The research may also lead to practical applications such as a more intuitive remote control for robots, treatments for phantom limb pain in amputee patients, and possible treatments for anorexia.
The research is a continuation of a related study, carried out by the same group last year, in which scientists managed to convince volunteers that they had had an out-of-body experience. It was the first time it was done in a laboratory and it showed, among other things, that the highly spiritual experiences that patients sometimes have on the operating table can have a scientific explanation.
“We are interested in how normal perception works; how we recognize our own body. And we investigated it by studying these perceptual illusions, ”said Dr. Henrik Ehrsson of the Karolinska Institute in Sweden. "Fundamentally it depends on the visual perspective and the so-called multisensory integration or combination of visual and tactile signals."
In the new study, Ehrsson and her colleague, Valeria Petkova, attached two cameras to the head of a mannequin. These were connected to two small screens placed in front of the subjects' eyes, creating the illusion that the person was seeing through the eyes of the mannequin. That way, for example, when they looked down they saw the body of the mannequin instead of their own.
To create the illusion of occupying the mannequin's body, the team struck the subject's abdomen and the manikin's abdomen at the same time, while the subject viewed the movement of the blow through cameras attached to the manikin's head. As a result, the subjects reported experiencing a strong feeling that the dummy's body was theirs. The technique is similar to the "rubber hand illusion", in which it is possible to convince a subject that a rubber hand is theirs, but this is the first time that the illusion has spread to the entire body. .
The illusion was so convincing that when the researchers threatened the mannequin with a knife, they recorded an increase in the subject's skin conductance, the indicator of stress on which lie detection polygraphs work. "This shows how easy it is to change the brain's perception of the physical self," said Ehrsson, who led the project.
"By manipulating sensory impressions, it is possible to deceive the self not only to believe it is outside its body, but also inside other bodies."
It got even stranger when researchers replaced the mannequin with someone else. After carrying out the same double attack routine, the subjects were convinced that they were occupying the body of another person. The illusion remained even when the other person turned and shook the subject's hand, feeling that he was shaking hands with himself.
Source: The Guardian Science