Phantoms in the Brain: Probing the Mysteries of the Human Mind (13 page)

So I hooked up the student volunteers to a GSR device while they stared at the table. I then stroked the hidden hand and the table surface simultaneously for several seconds until the student started experiencing the table as his own hand. Next I bashed the table surface with a hammer as the student watched. Instantly, there was a huge change in GSR as if I had smashed the student's own fingers. (When I tried the control experiment of stroking the table and hand out of sync, the subject did not experience the illusion and there was no GSR

response.) It was as though the table had now become coupled to the student's own limbic system and been assimilated into his body image, so much so that pain and threat to the dummy are felt as threats to his own body, as shown by the GSR. If this argument is correct, then perhaps it's not all that silly to ask whether you identify with your car. Just punch it to see whether your GSR changes. Indeed the technique may give us a handle on elusive psychological phenomena such as the empathy and love that you feel for a child or spouse.

If you are deeply in love with someone, is it possible that you have actually become part of that person?

Perhaps your souls—and not merely your bodies—have become intertwined.

Now just think about what all this means. For your entire life, you've been walking around assuming that your

"self is anchored to a single body that remains stable and permanent at least until death. Indeed, the "loyalty"

of your self to your own body is so axiomatic that you never even pause to think about it, let alone question it.

Yet these experiments

suggest the exact opposite—that your body image, despite all its appearance of durability, is an entirely transitory internal construct that can be profoundly modified with just a few simple tricks. It is merely a shell that you've temporarily created for successfully passing on your genes to your offspring.

He refused to associate himself with any investigation which did not tend towards the unusual, and even the
fantastic.

—
Dr. James Watson

David Milner, a neuropsychologist at the University of St. Andrews in Fife, Scotland, was so eager to get to the hospital to test his newly arrived patient that he almost forgot to take along the case notes describing her condition. He had to rush back to his house through a cold winter rain to fetch the folder describing Diane Fletcher. The facts were simple but tragic: Diane had recently moved to northern Italy to work as a freelance commercial translator. She and her husband had found one of those lovely old apartments near the medieval town center, with fresh paint, new kitchen appliances and a refurbished bathroom—a place nearly as luxurious as their permanent home back in Canada. But their adventure was short−lived. When Diane stepped into the shower one morning, she had no warning that the hot water heater was improperly vented. When the propane gas ignited to heat a steady flow of water flowing past red−hot burners, carbon monoxide built up in the small bathroom. Diane

48

was washing her hair when the odorless fumes gradually overwhelmed her, causing her to lose consciousness and fall to the tile floor, her face a bright pink from the irreversible binding of carbon monoxide to hemoglobin in her blood. She had lain there for perhaps twenty minutes with water cascading over her limp body, when her husband returned to retrieve something he had forgotten. Had he not gone home, she would have died within the hour. But even though Diane survived and made an amazing recovery, her loved ones soon realized that parts of her had forever vanished, lost in patches of permanently atrophied brain tissue.

When Diane woke from the coma, she was completely blind. Within a couple of days she could recognize colors and textures, but not shapes of objects or faces—not even her husband's face or her own reflection in a handheld mirror. At the same time, she had no difficulty identifying people from their voices and could tell what objects were if they were placed in her hands.

Dr. Milner was consulted because of his long−standing interest in visual problems following strokes and other brain injuries. He was told that Diane had come to Scotland, where her parents live, to see whether something could be done to help her. When Dr. Milner began his routine visual tests, it was obvious that Diane was blind in every traditional sense of the word. She could not read the largest letters on an eye chart and when he showed her two or three fingers, she couldn't identify how many fingers he held up.

At one point, Dr. Milner held up a pencil. "What's this?" he asked.

As usual, Diane looked puzzled. Then she did something unexpected. "Here, let me see it," she said, reaching out and deftly taking the pencil from his hand. Dr. Milner was stunned, not by her ability to identify the object by feeling it but by her dexterity in taking it from his hand. As Diane reached for the pencil, her fingers moved swiftly and accurately toward it, grasped it and carried it back to her lap in one fluid motion. You'd never have guessed that she was blind. It was as if some other person—an unconscious zombie inside her—had guided her actions. (When I say zombie I mean a completely nonconscious being, but it's clear that the zombie is not asleep. It's perfectly alert and capable of making complex, skilled movements, like creatures in the cult movie
Night of the Living Dead.)

Intrigued, Dr. Milner decided to do some experiments on Diane's covert ability. He showed her a straight line and asked, "Diane, is this line vertical, horizontal or slanted?"

"I don't know," she replied.

Then he showed her a vertical slit (actually a mail slot) and asked her to describe its orientation. Again she said, "I don't know."

When he handed her a letter and asked her to mail it through the slot, she protested, "Oh, I can't do that."

"Oh, come on, give it a try," he said. "Pretend that you're posting a letter."

Diane was reluctant. "Try it," he urged.

Diane took the letter from the doctor and moved it toward the slot, rotating her hand in such a way that the letter was perfectly aligned with the orientation of the slot. In yet another skilled maneuver, Diane popped the letter into the opening even though she could not tell you whether it was vertical, horizontal or slanted. She carried out this instruction without any conscious awareness, as if that very same zombie had taken charge of the task and effortlessly steered her hand toward the goal.1

Diane's actions are amazing because we usually think of vision as a single process. When someone who is obviously blind can reach out and grab a letter, rotate the letter into the correct position and mail it through an 49

opening she cannot "see," the ability seems almost paranormal.

To understand what Diane is experiencing, we need to abandon all our commonsense notions about what seeing really is. In the next few pages, you will discover that there is a great deal more to perception than meets the eye.

Like most people, you probably take vision for granted. You wake up in the morning, open your eyes and,
voilà,
it's all out there in front of you. Seeing seems so effortless, so automatic, that we simply fail to recognize that vision is an incredibly complex—and still deeply mysterious— process. But consider, for a moment, what happens each time you glance at even the simplest scene. As my colleague Richard Gregory has pointed out, all you're given are two tiny upside−down two−dimensional images inside your eyeballs, but what you perceive is a single panoramic, right−side−up, three−dimensional world. How does this miraculous transformation come about?2

Many people cling to the misconception that seeing simply involves scanning an internal mental picture of some kind. For example, not long ago I was at a cocktail party and a young fellow asked me what I did for a living. When I told him that I was interested in how people see things— and how the brain is involved in perception—he looked perplexed. "What's there to study?" he asked.

"Well," I said, "what do you think happens in the brain when you look at an object?"

He glanced down at the glass of champagne in his hand. "Well, there is an upside−down image of this glass falling in my eyeball. The play of light and dark images activates photoreceptors on my retina, and the patterns are transmitted pixel by pixel through a cable—my optic nerve— and displayed on a screen in my brain. Isn't that how I see this glass of champagne? Of course, my brain would need to make the image upright again."

Though his knowledge of photoreceptors and and optics was impressive, his explanation—that there's a screen somewhere inside the brain where images are displayed—embodies a serious logical fallacy. For if you were to display an image of a champagne glass on an internal neural screen, you'd need another little person inside the brain to see that image. And that won't solve the problem either because you'd then need yet another, even tinier person inside his head to view that image, and so on and so forth, ad infinitum. You'd end up with an endless regress of eyes, images and little people without really solving the problem of perception.

So the first step in understanding perception is to get rid of the idea of images in the brain and to begin thinking about symbolic descriptions of objects and events in the external world. A good example of a symbolic description is a written paragraph like the ones on this page. If you had to convey to a friend in China what your apartment looks like, you wouldn't have to teletransport it to China. All you'd have to do would be to write a letter describing your apartment. Yet the actual squiggles of ink—the words and paragraphs in the letter—bear no physical resemblance to your bedroom. The letter is a symbolic description of your bedroom.

What is meant by a symbolic description in the brain? Not squiggles of ink, of course, but the language of nerve impulses. The human brain contains multiple areas for processing images, each of which is composed of an intricate network of neurons that is specialized for extracting certain types of information from the image.

Any object evokes a pattern of activity—unique for each object—among a subset of these areas. For example, when you look at a pencil, a book or a face, a different pattern of nerve activity is elicited in each case,

"informing" higher brain centers about what you are looking at. The patterns of activity symbolize or represent visual objects in much the same way that the squiggles of ink on the paper symbolize or represent your bedroom. As scientists trying

50

the real world, a convex object bulging toward you would be illuminated on the top whereas a cavity would receive light at the bottom. Given that we evolved on a planet with a single sun that usually shines from on high, this is a reasonable assumption.4 Sure, it's sometimes on the horizon, but statistically speaking the sunlight usually comes from above and certainly never from below.

Not long ago, I was pleasantly surprised to find that Charles Darwin had been aware of this principle. The tail feathers of the argus pheasant have striking gray disk−shaped markings that look very much like those you see in Figure 4.3; they are, however, shaded left to right instead of up and down. Darwin realized that the bird might be using this as a sexual "come hither" in its courtship ritual, the striking metallic−looking disks on the feathers being the avian equivalent of jewelry. But if so, why was the shading left to right instead of up and down? Darwin conjectured correctly that perhaps during courtship the feathers stick up, and indeed this is precisely what happens, illustrating a striking harmony in the birds' visual system between its courtship ritual and the direction of sunlight.

Even more compelling evidence of the existence of all these extraor−

Figure 4.2
A mixture of eggs and cavities. The shaded disks are all identical except that half of them are light
on top and the rest are dark on top. The ones that are light on top are always seen as eggs bulging out from
the paper, whereas the ones that are dark on top are seen as cavities. This is because the visual areas in your
brain have a built−in sense that the sun is shining from above. If that were true, then only bulges (eggs)
would be light on top and concavities would be light below.