The Man Who Wasn't There: Investigations into the Strange New Science of the Self (26 page)

But Brugger never actually performed the experiment in a rigorous laboratory setting and so never published the results, though it did get
mentioned in an article in
Science
.

He credits American psychologist George Malcolm Stratton (1865–1957) as the inspiration for this experiment. Stratton had spent a good part of his career at the University of California, Berkeley. He is best known for “
perhaps the most famous experiment in the whole of experimental psychology.” Stratton fashioned a contraption that allowed him to see upside down. He walked around with this device on his right eye. He blacked out the left eye, because seeing upside down with both eyes was extremely disorienting. For three days and a total of 21.5 hours, he did nothing but use this device. When he went to bed, he strapped his eyes shut. While the primary motivation for the experiment was to understand visual perception, Stratton experienced other subtle changes in bodily perception. For instance, if he stretched out his hand to touch something, because he was seeing everything upside down, the hand would enter the visual field from above rather than below. Soon, “
parts of my body . . . were seen to be in another position.”

Stratton realized that he was onto something. In 1899, he
published another paper, in which he described a crazier experiment, this time with mirrors. He built a frame that he affixed to his waist and shoulders. The frame held a mirror horizontally above his head. He used the frame to position another mirror at a forty-five-degree angle in front of his eyes, so that it reflected the image from the overhead horizontal mirror directly into his eyes. The net effect was that Stratton was seeing himself and the space around him from the perspective
of someone looking down at his head from above. He made sure that no other light entered his eyes. Again, he walked around with this contraption for three days, for a total of twenty-four hours, with his eyes blindfolded when he was not experimenting and when he slept. Doing so, he was able to create a disharmony between sight and touch: when he’d reach out to touch something, his hands felt the touch, but his eyes told him that the touch was somewhere else entirely. It was now up to the brain to bring everything back into harmony, with interesting consequences.

Because Stratton was seeing his own body from above and nothing else, he had to pay close attention to this visual image to guide his actions and movements. By afternoon on the second day he began to notice that the reflected image sometimes felt like his body. This feeling became more persistent on the third day, especially when he was walking with ease and speed, not making any special effort to differentiate between where he was perceiving his body to be and where he “knew” his body to be. “
In the more languidly receptive attitude during my walk, I had the feeling that I was mentally outside my own body,” he wrote. Stratton had induced in himself an out-of-body experience.

Out-of-body experiences, autoscopic hallucinations, and doppelgänger phenomena are probably our best window on some very basic aspects of our sense of the bodily self. It’s become increasingly clear that the brain’s representation of one’s body and our conscious experience of it underpin self-consciousness. Having a bodily self, or being embodied, means several things. At the very fundamental level, it situates the center of our awareness. You are in a body that feels like it is yours—this is the sense of self-identification and body ownership. You
also feel that the body occupies a certain volume in physical space and you are located in that volume—the sense of self-location. Finally, you look out at the world from a point behind your eyes and you have the sense that this vantage point is yours and yours alone—you have what philosophers call a first-person perspective on the world.

The rubber-hand illusion is a classic example of how aspects of this bodily self can be disrupted. As we saw in chapter 3, when an experimenter strokes a visible rubber hand and the hidden real hand synchronously, the rubber hand is temporarily incorporated into one’s bodily self. We feel touch at the location of the rubber hand and there’s a sense of ownership of this otherwise lifeless object.

Henrik Ehrsson’s team at the Karolinska Institute in Stockholm, Sweden, got people to experience the rubber-hand illusion while they lay inside an fMRI scanner. The findings were revealing.
The strength of the illusion was strongly correlated with activity in the premotor cortex, a region in the brain that forms a network with the cerebellum and with parietal areas that process vision and touch. Parts of the parietal brain regions integrate vision, touch, and proprioception, and it’s well known that people with parietal lesions sometimes deny ownership of their limbs.

Neuroscientists think that the so-called multisensory integration of various sensations is responsible for giving us a sense of ownership over our body and body parts. Normally, vision, touch, and proprioceptive sensations all match up. They are congruent, and it’s this congruency that’s key to giving a body part a sense of
mineness
. During the rubber-hand illusion, proprioceptive distortions are kept to a minimum by keeping the real hand relaxed and not too far from the rubber hand. The brain erroneously integrates the misleading visual sensations and the real sensations of touch, and decides that the rubber
hand is real. That’s why we can lose ownership of the actual hand and gain ownership of the rubber hand. This switch in ownership has real physiological consequences: for instance, the
temperature in the real hand drops by nearly 1 degree Celsius (about 2 degrees Fahrenheit)—an autonomic nervous system response that’s not under conscious control.

In Ehrsson’s lab, I got to experience the rubber-hand illusion for the first time (having failed in earlier attempts). Arvid Guterstam, a postdoc in Ehrsson’s lab, played host and subjected me to the illusion. Having done it innumerable times, he was quite the expert. I felt the illusion of owning the rubber hand rather strongly. But then Guterstam did something that jolted me further. Once I began feeling the touch in the location of the rubber hand, he lifted his brush a couple of inches above the rubber hand and continued moving the brush synchronously with the movement of the brush on my real hand.

“What was that?” I said. “What’s happening? This is really weird.”

He was moving the brush in the air and I was feeling the touch of the brush in the space above the rubber hand.

It turns out the neurons in the premotor cortex have what’s called a receptive field—they fire not just when a body part is touched but when the proximal space around that body part is touched (this is called peripersonal space). My brain had remapped the location of my hand and centered it on the rubber hand. The space above the rubber hand had become my peripersonal space, and consequently a brushstroke in the space above the rubber hand was now registering as a touch at that location.

Ehrsson’s team has also shown that you don’t even need a rubber hand to experience the illusion: just the brush strokes on the hidden real hand combined with synchronous movements of a brush in empty
space, in a manner that’s suggestive of a hand there, is enough to generate the illusion of being touched at a location where there is no real hand.

Scientific explanations aside, I was thrilled to have finally experienced the illusion, and said so.

“You seem to have an easily fooled brain,” Guterstam quipped.

Fooling the brain to take ownership of a rubber hand is just one piece of the puzzle that is bodily self-consciousness. A hand is just a constituent of the bodily self. How much more can one manipulate the bodily self? Much, much more, as it turns out.

As a young man in the late 1970s and early 1980s, Thomas Metzinger felt conflicted about telling anyone about his out-of-body experiences. One of those happened when he was studying to become a philosopher, and intensely curious about altered states of consciousness. He was attending a highly regimented meditation retreat in the Westerwald, about sixty miles northwest of Frankfurt, Germany. Ten consecutive weeks were filled with yoga, breathing exercises, and individual and group meditation sessions. Metzinger immersed himself in all that was asked of him. One Thursday, the retreat organizers had baked a cake—to celebrate the teacher’s birthday. It was a rich, greasy cake. Metzinger ate some of it. Feeling unwell, he went to bed and fell asleep.

He woke up wanting to scratch his back, and realized he couldn’t move. His body was paralyzed. It was then that he felt himself spiraling out of his own body, up and in front of his bed. It was dark, so he didn’t actually turn around and see his body lying in bed. He was scared, but something scarier was to follow.

He suddenly realized that there was someone else breathing heavily in the room. “And then I panicked,” Metzinger told me as we sat at the dining table in his home in rural Germany, a few tens of miles east of Frankfurt. “Somebody was there; I couldn’t move my body, I was dissociated from my body. It was very unpleasant.” There was, of course, no one else in that room, and only many years later would Metzinger find explanations for such experiences in the scientific literature. It turns out that in certain dissociative states, you cannot recognize self-generated sounds as self-generated; in Metzinger’s case, he lost a sense of ownership of the sounds of his own breathing, hence the hallucination of someone breathing near him.

Metzinger alerted his meditation teachers, but to his dismay all they did was put him under a cold shower and tell him to meditate less (today, as someone who advocates meditation training in schools, Metzinger is concerned and critical that many meditation centers do not have staff trained to deal with altered states of consciousness or psychiatric emergencies).

Soon afterward, Metzinger moved to a remote region south of Limburg, to concentrate on writing his doctoral dissertation on the mind-body problem and also to deliberately confront himself with the consequences of solitude and boredom—a personal project. As a poor student, with little money to even call his friends in Frankfurt, he lived alone in a 350-year-old house, taking care of sheep and nineteen fishponds. He meditated a lot. And he had a few more unexpected, spontaneous out-of-body experiences. But by now, his curiosity and analytical mind had taken over: he wanted to understand his experiences. His extensive study of the scientific and philosophical literature was showing a complete lack of evidence that consciousness could be dissociated from the brain. Yet there he was, having extremely vivid
experiences of apparent dualism in which his conscious self was seemingly separated from his own body. And he knew he could tell no one except his closest friends.

So, as a budding philosopher of mind and cognitive science getting grounded in empirical data, he tried conducting his own experiments while in those altered states, to see if brain and consciousness could indeed be separated and whether that would lead to conclusive, verifiable observations. He learned to control his initial fear during his OBEs, but not entirely. Despite his efforts, he uncovered not a shred of evidence that his conscious self had actually dissociated from his body.

Meanwhile, he had conversations and exchanges with other researchers. One British psychologist, Susan Blackmore, after fierce and extended discussions, finally managed to convince him that his OBEs were actually hallucinations. She quizzed him about how he moved from his physical body, which was lying in bed, to the windowsill during an out-of-body experience. Did he walk over there? Did he fly? Metzinger realized that his movements were unlike anything that happens in real life. “Sometimes, it’s almost as if the moment you think you want to go there you are already there,” he told me. Blackmore argued that he was hallucinating, moving between mental representations of, say, the bed and the window, jumping or gliding from landmark to landmark in his mind. Metzinger realized that he was not moving in his bedroom but within an internal model of his bedroom created by his brain.

Another really strange experience convinced him even more that he was indeed hallucinating. He had an OBE, and when he returned to his body he ran to wake up his sister, to tell her of his experience. “It’s quarter to three, can’t it wait until breakfast?” she told him. But
then an alarm went off, and Metzinger woke up—again. He wasn’t in Frankfurt in his parents’ house with his sister. Rather, he had been taking an afternoon nap in a house that he shared with four other students. He had experienced what dream researchers call “false awakening”: a dream that he had woken up. But prior to the false awakening, he had dreamed he had an OBE. “It began to dawn on me that there are multiple transitions between different classes of altered states of consciousness,” he said. He had been having such vivid out-of-body experiences that he had even begun dreaming about them.