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Traveling outside your own body is as easy as a video illusion, according to new research. Simply sit in front of two cameras filming your back. Place a special headset over your eyes; it will display the images from the left camera to your left eye and the right camera to your right eye. Then enlist a friend to simultaneously stroke your chest and perform a similar motion just below the cameras' fields of view. Within a minute, you will suddenly be overcome by the strange sensation that you are sitting where the cameras are rather than in your own body.
For a quicker, less powerful jaunt outside your bodily confines, try the double-mirror trick: Position two mirrors facing each other and then lean toward one so that two thirds of your face is reflected in it. Scratch your cheek and stare deep into the hall of mirrors you have created, past your original reflection, past the image of your back, and settle on the third reflection—your own face but slightly obscured. Within seconds, you won't recognize that reflection as you, says neuroscientist Eric Altschuler of the University of Medicine & Dentistry of New Jersey in Newark, who reported the phenomenon in the April issue of Perception.
Admittedly, neither of these illusions precisely match the classic example of the out-of-body experiences reported by patients near death who say they floated out of their bodies but were able to continue observing scenes from above or elsewhere in the room. But two studies published this week in Science show how the self and body can be disconnected, using video cameras.
"We found a method to change the perceived location of the body in space even if that means that one is located outside the physical body," cognitive neuroscientist Henrik Ehrsson of the Karolinska Institute in Stockholm says. "They see themselves sitting in the middle of the room, but they feel themselves sitting in a corner of the room."
He tested seven men and 11 women using the headset and camera method. All of the subjects reported feeling whisked across the room when stroked. "I felt as though I was outside my body and looking at myself from the back," one volunteer offered; others spontaneously giggled or otherwise expressed amusement when subjected to the odd effect.
In an attempt to test the strength of the illusion, Ehrsson threatened the illusory bodies of eight men and four women with a hammer. All of the subjects flinched or winced in alarm and the electrical currents in their skin jumped even though Ehrsson had explicitly promised not to hurt any of them at the beginning of the session. " You can't think [the illusion] away, it's not a high-level cognitive thing," he says. "It's a perceptual illusion and you don't have ulterior [(intellectual)] control."
In similar work, Olaf Blanke of the Brain Mind Institute at the Swiss Federal Institute of Technology in Lausanne and his colleagues persuaded subjects that they were not standing where they really were by simultaneously stroking their backs and projecting a virtual reality image into headgear of them standing two meters (2.2 yards) in front of their true location.
The nine women and five men were moved from their original spot and, when asked to return to it, moved toward the virtual location by an average of 24 centimeters (9.4 inches). [see video] Other subjects shown a mannequin of a blonde woman (instead of virtual images of themselves) also drifted in her direction and even those fed an image of a simple metal block moved slightly toward it. "We believe that the almost [statistically] significant drift in the object condition is actually a relevant result and needs to be tested in further experiments," Blanke says.