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The Out-of-Body ElectricCan scientists make your soul fly away?

By Daniel Engber
Posted Thursday, Aug. 23, 2007, at 6:01 PM ET

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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?

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Daniel Engber is an associate editor at Slate. He can be reached at .
Photograph of an out-of-body-experience experiment courtesy Henrik Ehrsson.
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Remarks from the Fray:

Favoring the premise that the simplest explanation is the best one, I suspect that most of these experiences are dreams. Though dreams are not my area of interest, I am a clinician and researcher in sleep disorders. I have had a few patients describe out of body experiences to me, and they invariably occur while the patient is sleeping, never while they are awake. But I admit I've only had a handful of patients tell me about them, so I'm no expert.

I suspect the OBE is a specific subtype of Lucid Dream - a dream in which the subjects have some awareness of being in the dream, and retain their own personality and memories (which are usually lost or distorted in normal dreams). Some of my patients have even volunteered that the OBEs most frequently occur in the twilight state between wakefulness and sleep (i.e. "half-asleep") and that also happens to be prime territory for lucid dreams.

--mnemon

(To reply, click here.)

Don't know whether the phrase has been coined yet, but I'd call this phenomenon "sensory consonance", meaning that multiple senses are stimulated in a consistent way to generate a realistic feeling. Sensory consonance is what we experience all the time every day. The experimenters took advantage of sensory consonance to induce a real feeling of an unreal situation.

"Sensory dissonance" happens if different senses give you conflicting information. This happened when the hammer was swung in the experiment. Your eyes say you've been hit, but your nose says otherwise.

This conflict can induce an uneasy, even sickening feeling. If you've ever been to an IMAX movie, you've probably experienced it. The movie screen fills your whole field of vision, and it tells you that you're swooping through the Grand Canyon, or something equally engaging. But the seat of your pants tells you you're sitting still. Depending on your constitution, you can get serious motion sickness during those swooping scenes.

I work in Iowa City, home of the National Advanced Driving Simulator. The "advanced" simulator has a 360-degree screen and a sophisticated motion base. The video and motion respond very realistically to your driving inputs, accelerating and turning through a virtual landscape. An earlier, "pre-advanced" simulator had the video, but not the motion base. The video responded realistically to your inputs, but the "car" did not move. I drove this old simulator once. During gentle maneuvers, it felt OK. But during the more evasive maneuvers I felt some serious motion sickness.

And heaven help you if the software isn't working right on the advanced simulator, because the steering wheel/gas pedal, the video, and the seat of your pants can be telling you three different things.

--alewbail

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Both Persinger and Erhsson miss the point of true out of body experiences. They've crafted methods of creating an as-if experience, but what they describe is a hallucination. The experimental results are to a real out of body experience as Wilder Penfield's brain-stimulation hallucinations are to real music and images.

As anyone who's had an OBE can tell you, you see things you really can't have seen any other way. The top of your own head, for example. The position of others around you from above, and the location of landmarks you can't possibly have seen from the ground. Simulating that sense of floating behind yourself with a camera may feel like the real thing, as may stimulating the angular gyrus with an electrode. But it doesn't prove or disprove the reality of OBE. I'm not saying OBE is a supernatural or spiritual experience, I'm just saying that it's not imaginary either. When you have a surgeon relating his personal experience with it to Oliver Sacks (in a recent New Yorker), it gets harder to dismiss every incident as wishful thinking or brain damage.

--Isonomist

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