Wednesday, December 03, 2008

Scientist research "body swap" illusion

Have you ever wondered about waking up in someone else's body? If you're like me you have read all kinds of stories on this subject - from brain transplants to robot bodies which most often go awry because the "human" part can not come to terms with not being in their "own" body. Or something weird like Heinlein's I will fear no Evil.

I first started hearing about an odd illusion when Swedish researches found that a subject could be "fooled" into believing that someone elses hand or an artificial hand was their own. This was done by concealing the subject's hand and displaying the false limb. The subjects hand was touched exactly at the same time as the fake hand was. The test subjects report feeling as though the false hand was in fact theirs.

In a more recent study. Cognitive neuroscientists at the Swedish medical university Karolinska Institutet have succeeded in making subjects perceive the bodies of mannequins and other people as their own.

In the first experiment, the head of a shop dummy was fitted with two cameras connected to two small screens placed in front of the subjects' eyes, so that they saw what the dummy "saw." When the dummy's camera eyes and a subject's head were directed downwards, the subject saw the dummy's body where he/she would normally have seen his/her own.

The illusion of body-swapping was created when the scientist touched the stomach of both with two sticks. The subject could then see that the mannequin's stomach was being touched while feeling (but not seeing) a similar sensation on his/her own stomach. As a result, the subject developed a powerful sensation that the mannequin's body was his/her own.

In another experiment, the camera was mounted onto another person's head. When this person and the subject turned towards each other to shake hands, the subject perceived the camera-wearer's body as his/her own.

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