Scientists Report Mental 'Body-Swapping'

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Tuesday, December 2, 2008; 12:00 AM

TUESDAY, Dec. 2 (HealthDay News) -- The illusion of body-swapping -- making people perceive the bodies of mannequins and other people as their own -- has been achieved by Swedish neuroscientists.

In one experiment, the team fitted the head of a mannequin with two cameras connected to two small screens placed in front of volunteers' eyes, so that they had the same view as the mannequin.

When the mannequin's camera eyes and a participant's head were directed downwards, the participant saw the mannequin's body where the person would normally have seen their own body.

The researchers created the illusion of body-swapping by touching the stomach of both the mannequin and the volunteer with sticks. The person saw the mannequin's stomach being touched while feeling (but not seeing) a similar sensation on their own stomach. As a result, the person developed a strong belief that the mannequin's body was actually their own.

"This shows how easy it is to change the brain's perception of the physical self. By manipulating sensory impressions, it's possible to fool the self not only out of its body but into other bodies, too," project leader Henrik Ehrsson, of the Karolinska Institute in Stockholm, said in a news release.

In another experiment, a camera was mounted on one person's head and screens were mounted in front of another person's eyes. When the person with the camera and the person with the screens turned towards each other to shake hands, the person with the screens perceived the camera-wearer's body as his/her own.

"The subjects see themselves shaking hands from the outside, but experience it as another person. The sensory impression from the handshake is perceived as though coming from the new body, rather than the subject's own," study co-author Valeria Petkova said in the news release.

This illusion worked even when two people looked different or were of different sexes. It did not work when a non-humanoid object -- such as a chair or large block -- was used.

The research, published online Wednesday in the journal PLoS One, could prove useful in virtual reality applications and in robot technology, the team said.

More information

There's more on how the brain works at McGill University.

SOURCE: Public Library of Science, news release, Dec. 2, 2008



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