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Body swapping

Extract from Chapter 12: The Space Element

Andrew, an American student who has volunteered to participate in a psychology study, walks into Dr. Henrik Ehrsson’s laboratory in the Karolinska Institute in Stockholm and stands opposite a plastic mannequin. Ehrsson’s colleague, doctoral student Valeria Petkova, attaches electrodes to the middle and index fingers of Andrew’s left hand, and then slips a video headset over his eyes. Through the headset, Andrew sees the images generated by two video cameras that are fixed to the mannequin’s head and pointed down at its feet.

Andrew is now seeing what the mannequin sees, so when he tilts his head forward and matches the mannequin’s downward gaze, he immediately starts to have a sense that the mannequin is “him.” That feeling becomes even more convincing when Petkova takes a marker and simultaneously strokes Andrew’s belly and that of the mannequin. Andrew can see only the mannequin’s abdomen being touched, but he can feel the pen brushing against his own body. The moment that the touch happens, Andrew, with a kind of jolt, feels that he’s actually inside the mannequin’s body. His sense of identification with his own body “snapped,” he said later. Next, Petkova pulls the blade of a sharp knife across the belly of the mannequin. Although he knows the researchers wouldn’t harm him, Andrew still feels the desire to pull away, and the electrodes on his fingertips register increased electrical activity—a clear indication of anxiety.

In a later experiment, Andrew stands opposite Petkova herself. She’s now wearing the mannequin’s video cameras, so that Andrew sees himself from her perspective. As before, he quickly begins to feel that he is in another body—her body—seeing himself from the outside. The two hold hands, and Andrew experiences Petkova’s grip as his own. She squeezes his hand, and he feels that he’s doing the squeezing. The fact that the two people are of different genders has no effect on the illusion, Ehrsson and Petkova have found. A man can easily identify with a female body and vice versa. Typically, it only takes 10 to 12 seconds for a volunteer to abandon his or her body and to identify with that of their partner or a mannequin, and 70 to 80 percent of volunteers experience the illusion very strongly.

The Space Element brings together the first four element, with the internal element representing the human body as a whole—the shape, form, or appearance that we identify with. Although we undoubtedly cling to our bodies, the identification we have with them turns out to be surprisingly flexible.

It’s even possible to persuade people that they are outside of their bodies altogether. In another experiment, Ehrsson filmed the backs of volunteers with stereo video cameras. As in the experiment above, the volunteers wore headsets that allowed them to see themselves. They reported that they felt as if they were outside and about two meters behind their bodies. When Ehrsson swung a hammer in the direction of the cameras, which were safely behind the participants’ actual bodies, the volunteers experienced anxiety and showed measurable signs of emotional and physiological stress.

Electrical stimulation to specific spots in the brain can also produce out-of-body-experiences. A Swiss team at the Federal Institute of Technology in Lausanne, led by Bigna Lenggenhager, found with one woman that stimulation to a brain region called the temporal parietal junction resulted in a sensation that she was hanging from the ceiling, looking down at her body. The woman had a normal psychiatric history and was reportedly stunned by the bizarre nature of her experience.63

At first sight it seems extraordinary that our sense of self can be so easily manipulated. With only ten to twelve seconds of seeing our own body from the outside, or a tiny jolt of electricity to the brain, we can be induced to abandon our life-long sense of inhabiting the body we have grown up with. Then again, perhaps this isn’t so surprising. Imagine yourself as a newborn baby. You have to learn to coordinate the movements of your body. You have to learn what arms, hands, and legs are for, how to move them in a coordinated way, and how to keep track of where they are. But most fundamentally, you have to learn that these are your body parts. We’ve all been through the stage of having to learn to initially identify something as our bodies. And that process of identification is ongoing—we have to continually adjust our sense of what the body is, because the body changes. As we grow, the size, proportions, and strength of the body change, meaning that we continually undergo a shift in our sense of what constitutes the physical self. If we couldn’t make rapid adjustments to our sense of what our body is and how it functions, it would be hard to adapt our style of walking when we’d injured a foot, or adjust the amount of effort we make when carrying something heavy upstairs, never mind to adapt to dramatic changes to the body such as losing a limb.