Two teams of neuroscientists have made a breakthrough in the study of "out-of-body experiences," according to this week's issue of Science. About one in 10 people report having had the strange sensation of floating away from their bodies at some point in their lives. According to the new studies, it's now possible to induce that feeling of astral projection in the lab.
There have been similar claims in the past: At Laurentian University in Canada, Michael Persinger has used a helmet studded with magnets to create quasi-mystical experiences, including—for some subjects, at least—the sensation of drifting outside the body. But the authors of the new research manage the feat without any neural poking or zapping. Instead, they use little more than a pair of virtual-reality goggles.
The new approach seems to work as advertised—test subjects said the experiment made them feel like they were outside of their own bodies. But that's where the story ends. The out-of-body VR setup does a great job of mimicking the superficial aspects of the out-of-body experience. But it teaches us very little about how or why it happens in real life.
The first of these studies, titled "The Experimental Induction of Out-of-Body Experiences" and conducted by Henrik Ehrsson, shows that you can create something like an OBE using special effects. First, you sit in a chair and don a pair of virtual-reality goggles that are connected to a 3-D camera that's pointed at the back of your head. Looking through these goggles already makes you feel, at least to some extent, as though you're where the camera is, sitting a few feet behind your own body. (It's possible to create a similar feeling of displacement without looking at your own head: If the goggles were showing a three-dimensional video feed of the bathroom, you might feel a bit like you were in the bathroom.)
Now, Ehrsson tries to make the effect more realistic. He starts rubbing your chest, while at the same time reaching a hand toward the camera that's providing the video feed. As you feel the touch on your chest, you're also seeing an arm reach below your video "eyes." This combination, it turns out, makes you feel even more like you're sitting behind yourself. (Likewise, if you were watching a video feed of the bathroom and the experimenter flushed a toilet, it would make you feel even more like you were in the bathroom.)
To measure the strength of this illusion, Ehrsson conducts one more test. About a minute into the experiment, he suddenly picks up a hammer and swings it toward the empty space just below your camera "eyes." At the same time, he measures your emotional arousal using skin conductance electrodes: The more realistic the experience, the more charged up you'll get at the sight of the hammer coming toward your virtual nose.
The study confirmed that synchronized touching makes the illusion more vivid. ("Wow!" giggled one subject. "I felt as though I was outside my body and looking at myself from the back!") If you saw Ehrsson rub your imaginary chest at the same time that you felt it happening, you'd be more startled when he swung the hammer. In fact, this "multisensory correlation" of vision and touch helps you figure out your position in space—and decide whether you're in body or out of body. (The second paper, by Bigna Lenggenhager and Olaf Blanke, uses a different setup to arrive at the same conclusion; click here for more details.)
This result seems to corroborate previous work on out-of-body experiences. In 2004, Blanke's group showed that damage to the brain's temporo-parietal junction can make patients feel like they're floating above themselves and looking down. That patch of cortex is thought to be important for combining different kinds of sensory input, like vision and touch. If your temporo-parietal junction malfunctions, you might lose your ability to correlate your senses and forget where you are.
But the new studies don't provide much new insight into how a brain malfunction might create the out-of-body experience. The correlation of multiple senses improves all sorts of illusions—not just the mystical, floaty ones. Let's say I showed you a photograph of a poisonous snake baring its fangs. You'd know it's not going to bite you, but your skin conductance response might show a modest increase in arousal. A movie of a rattlesnake shaking its tail or snapping its jaws would elicit a more pronounced response, and a three-dimensional projection complete with hissing sound effects would be scarier still. And if you could also feel the snake slithering against your legs, you'd be terrified—after all, better feedback always makes for a more realistic experience. (This is why vibrating controllers make video games more fun: You connect the jolt in your hand with the image on the screen.)
There's no out-of-body experience in our snake example, just the illusion of a dangerous animal. Multisensory correlation—i.e., seeing, hearing, feeling—still enriches the effect. By that token, Ehrsson could have written a paper called "The Experimental Induction of Snake Hallucinations" and concluded that multisensory correlation underlies the perception of reptiles. But it's more tempting, and more interesting, to explain out-of-body experiences than reptile mirages. By pointing the cameras at the subjects' own heads, the researchers can create a nifty illusion while appealing to grandiose existential questions about consciousness: How do our brains combine our senses to decide where and what we are?
Those questions have been studied extensively on a smaller scale. The "rubber hand illusion," for example, can trick you into losing track of a single body part. Someone strokes a rubber hand in front of you while at the same time stroking your real hand out of view. After a while, you start to think the rubber hand is your own. You can also induce a simple out-of-hand experience for yourself with the "crossed-hand illusion." Our susceptibility to these sorts of illusions turns out to be very useful. When you're wielding a hammer, your brain can extend your body image to include the tool. It may even take a mild sort of out-of-hand illusion to use a computer mouse or trackpad—the cursor becomes a proxy for your hand or fingertip.
The new studies in Science show that these hand and limb illusions can be extended to the whole person—they've replaced the rubber hand with a rubber body. By creating vivid multisensory feedback, the experimenters show that you can make someone feel like they've been shifted in space, from head to toe. That's interesting on its own terms, and it could lead to improved virtual-reality interfaces (not to mention awesome video games).
But it's not clear how the full-body illusions relate to the out-of-body experiences that occur by accident, the ones we're inclined to associate with celestial lights, silver cords, and other mystical phenomena. After all, Ehrsson has created an illusion to match a definition; for him, an out-of-body experience is one in which "a person who is awake sees his or her body from a location outside the physical body." If that's all there is to it, then all you need is a mirror! Watching a video of the back of your head may give you an uncanny feeling of being disembodied, but it doesn't get at the bigger question of how a mental hiccup can cause this experience in the real world. The lab-induced sensation might tweak a totally different part of the brain. We're not any closer, in the end, to answering the most interesting question of all: When I float above my bed and drift into the stars above, what the hell is going on?