December 02, 2008

Swapping Bodies: Researchers Fool Brains to Think They're In Mannequins

Swedish researchers Henrik Ehrsson and Valeria Petkova have used technology to fool the brains of subjects into thinking that they're in mannequins instead of their usual bodies. It's pretty trippy stuff.

Cognitive neuroscientists at the Swedish medical university Karolinska Institutet (KI) have succeeded in making subjects perceive the bodies of mannequins and other people as their own. The findings are published in the online, open-access journal PLoS ONE, December 3.

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...

The strength of the illusion was confirmed by the subjects' exhibiting stress reactions when a knife was held to the camera wearer's arm but not when it was held to their own.

The illusion also worked even when the two people differed in appearance or were of different sexes. However, it was not possible to fool the self into identifying with a non-humanoid object, such as a chair or a large block...

— Source: EurekAlert! Press Release

The paper, If I Were You: Perceptual Illusion of Body Swapping, goes into great detail about how and why all this works. For me, the takeaway message is that we can be fooled about things about which we are normally quite certain if we rely on our senses alone. If we can be tricked into thinking that we're not in our own body but within an inanimate, albeit anthropoid, object, we can be tricked into just about anything if some unbiased intermediate observer or technology isn't used to make sure that seeing is truly worth believing.

I'm led to wonder, too, about the so-called "out of body experience" reported by some people who have come near death. If the changes that cause the apparent projection of consciousness into a dummy (no cracks about Dubya, now!) can be induced by the application of cameras, and that experience is fundamentally electrochemical, then surely a similar effect might occur as a result of the illness or trauma that leads to a near-death experience.

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