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Imagine taking a short vacation from yourself.
A neuroscientist working in Britain has found a way to induce an out-of-body experience, a technique that makes people feel as if they are standing behind themselves, watching their own backs.
The work could lead to a new generation of virtual-reality video games that would create the sensation that players really are somewhere else.
It may also help scientists understand what happens in the brains of patients who have reported feeling as if they were floating above their bodies during a stroke, seizure or migraine.
Surveys suggest as many as one in 10 people have a similar experience, often after a traumatic event such as a car accident, or after using hallucinogenic drugs. People who feel they've been outside their bodies sometimes say that paranormal or supernatural forces have been at work.
Scientists seeking to understand what is really going on have been hampered by the difficulty of studying out-of-body experiences in the lab.
Now Henrik Ehrsson, working at University College London, has found a way to deliberately induce the sensation.
In his experiments, reported in Thursday's edition of the journal Science, volunteers sat in a chair and put on video-display goggles with a separate small screen for each eye.
Two cameras were set up two metres behind the chair, about the same distance apart as two eyes in a face. The image from the left video camera was fed into the left eye display; the one from the right went to the right. The participants see one 3-D image of themselves.
Then, the researcher touched the volunteer's chest with a plastic rod at the same time as he moved an identical rod toward the two cameras, aiming for chest level as well.
Eighteen of the 19 volunteers reported that they felt they were sitting behind their own bodies.
In a second experiment, when the researcher swung a hammer to the area just below the video cameras, the volunteers began to sweat, as if the hammer was heading toward their own necks.
“This was a bizarre, fascinating experience for the participants – it felt absolutely real for them,” Dr. Ehrsson says.
“This is essentially a means of projecting yourself, a form of teleportation. If we can project people into a virtual version of themselves, just imagine the implications. The experience of playing video games could reach a whole new level.”
But he didn't have video games in mind when he began the research. Dr. Ehrsson wanted to know why it is that we feel we are located inside our bodies. “I am interested in how the brain recognizes our own body,” he says.
Our eyes clearly play an important role in collecting indirect information about where we are located in space. In fact, Dr. Ehrsson compares his experiments to virtual eye surgery.
“If you can take someone's eyes, and move them to a different part of the room, would they feel as if they had moved to where their eyes are?”
The answer, according to his experiments, is yes. He is now planning follow-up work to see if he can induce an out-of-body experience in which people feel as if they are seeing themselves from above or from the side.
But is it the same as a spontaneous out-of-body experience? Dr. Ehrsson isn't sure it is as profound or dramatic, but says it appears to be a similar sensation.
He is not the only researcher working on out-of-body experiences. In Thursday's edition of Science, members of a Swiss team describe a similar set of experiments.
Bigna Lenggenhager, Olaf Blanke and his colleagues at the Swiss Federal Institute of Technology in Lausanne asked people to stand in front of a camera while wearing video-display goggles. They were shown three-dimensional images of their own backs.
A researcher then stroked their backs with a pen, at the same time as they looked at images of their body being stroked with the same instrument.
They reported that they felt as if their “virtual” back was their real back. The volunteers said they felt “weird” but didn't report the same kind of disembodiment as in a classic out-of-body experience.
In previous work, Dr. Blanke and his colleagues unintentionally induced out-of-body experiences in patients with epilepsy. They were implanting electrodes in the brains of the patients, who were conscious at the time.
