Any ape can reach for a banana, but only humans can reach for the stars. Apes live, contend, breed, and die in forests—end of story. Humans write, investigate, create, and quest. We splice genes, split atoms, launch rockets. We peer upward into the heart of the Big Bang and delve deeply into the digits of pi. Perhaps most remarkably of all, we gaze inward, piecing together the puzzle of our own unique and marvelous brain. It makes the mind reel. How can a three-pound mass of jelly that you can hold in your palm imagine angels, contemplate the meaning of infinity, and even question its own place in the cosmos? Especially awe inspiring is the fact that any single brain, including yours, is made up of atoms that were forged in the hearts of countless, far-flung stars billions of years ago. These particles drifted for eons and light-years until gravity and chance brought them together here, now. These atoms now form a conglomerate—your brain—that can not only ponder the very stars that gave it birth but can also think about its own ability to think and wonder about its own ability to wonder. With the arrival of humans, it has been said, the universe has suddenly become conscious of itself. This, truly, is the greatest mystery of all.
It is difficult to talk about the brain without waxing lyrical. But how does one go about actually studying it? There are many methods, ranging from single-neuron studies to high-tech brain scanning to cross-species comparison. The methods I favor are unapologetically old-school. I generally see patients who have suffered brain lesions due to stroke, tumor, or head injury and as a result are experiencing disturbances in their perception and consciousness. I also sometimes meet people who do not appear brain damaged or impaired, yet report having wildly unusual perceptual or mental experiences. In either case, the procedure is the same: I interview them, observe their behavior, administer some simple tests, take a peek at their brains (when possible), and then come up with a hypothesis that bridges psychology and neurology—in other words, a hypothesis that connects strange behavior to what has gone wrong in the intricate wiring of the brain.1 A decent percentage of the time I am successful. And so, patient by patient, case by case, I gain a stream of fresh insights into how the human mind and brain work—and how they are inextricably linked. On the coattails of such discoveries I often get evolutionary insights as well, which bring us that much closer to understanding what makes our species unique.
Consider the following examples:
Whenever Susan looks at numbers, she sees each digit tinged with its own inherent hue. For example, 5 is red, 3 is blue. This condition, called synesthesia, is eight times more common in artists, poets, and novelists than in the general population, suggesting that it may be linked to creativity in some mysterious way. Could synesthesia be a neuropsychological fossil of sorts—a clue to understanding the evolutionary origins and nature of human creativity in general?
Humphrey has a phantom arm following an amputation. Phantom limbs are a common experience for amputees, but we noticed something unusual in Humphrey. Imagine his amazement when he merely watches me stroke and tap a student volunteer’s arm—and actually feels these tactile sensations in his phantom. When he watches the student fondle an ice cube, he feels the cold in his phantom fingers. When he watches her massage her own hand, he feels a “phantom massage” that relieves the painful cramp in his phantom hand! Where do his body, his phantom body, and a stranger’s body meld in his mind? What or where is his real sense of self?
A patient named Smith is undergoing neurosurgery at the University of Toronto. He is fully awake and conscious. His scalp has been perfused with a local anesthetic and his skull has been opened. The surgeon places an electrode in Smith’s anterior cingulate, a region near the front of the brain where many of the neurons respond to pain. And sure enough, the doctor is able to find a neuron that becomes active whenever Smith’s hand is poked with a needle. But the surgeon is astonished by what he sees next. The same neuron fires just as vigorously when Smith merely watches another patient being poked. It is as if the neuron (or the functional circuit of which it is a part) is empathizing with another person. A stranger’s pain becomes Smith’s pain, almost literally. Indian and Buddhist mystics assert that there is no essential difference between self and other, and that true enlightenment comes from the compassion that dissolves this barrier. I used to think this was just well-intentioned mumbo-jumbo, but here is a neuron that doesn’t know the difference between self and other. Are our brains uniquely hardwired for empathy and compassion?
When Jonathan is asked to imagine numbers he always sees each number in a particular spatial location in front of him. All numbers from 1 to 60 are laid out sequentially on a virtual number line that is elaborately twisted in three-dimensional space, even doubling back on itself. Jonathan even claims that this twisted line helps him perform arithmetic. (Interestingly, Einstein often claimed to see numbers spatially.) What do cases like Jonathan’s tell us about our unique facility with numbers? Most of us have a vague tendency to image numbers from left to right, but why is Jonathan’s warped and twisted? As we shall see, this a striking example of a neurological anomaly that makes no sense whatsoever except in evolutionary terms.
A patient in San Francisco becomes progressively demented, yet starts creating paintings that are hauntingly beautiful. Has his brain damage somehow unleashed a hidden talent? A world away, in Australia, a typical undergraduate volunteer named John is participating in an unusual experiment. He sits down in a chair and is fitted with a helmet that delivers magnetic pulses to his brain. Some of his head muscles twitch involuntarily from the induced current. More amazingly, John starts producing lovely drawings—something he claims he couldn’t do before. Where are these inner artists emerging from? Is it true that most of us “use only 10 percent of our brain”? Is there a Picasso, a Mozart, and a Srinivasa Ramanujan (a math prodigy) in all of us, waiting to be liberated? Has evolution suppressed our inner geniuses for a reason?
Until his stroke, Dr. Jackson was a prominent physician in Chula Vista, California. Afterward he is left partially paralyzed on his right side, but fortunately only a small part of his cortex, the brain’s seat of higher intelligence, has been damaged. His higher mental functions are largely intact: He can understand most of what is said to him and he can hold up a conversation reasonably well. In the course of probing his mind with various simple tasks and questions, the big surprise comes when we ask him to explain a proverb, “All that glitters is not gold.”
“It means just because something is shiny and yellow doesn’t mean it’s gold, Doctor. It could be copper or some alloy.”
“Yes,” I say, “but is there a deeper meaning beyond that?”
“Yes,” he replies, “it means you have to be very careful when you go to buy jewelry; they often rip you off. One could measure the metal’s specific gravity, I suppose.”
Dr. Jackson has a disorder that I call “metaphor blindness.” Does it follow from this that the human brain has evolved a dedicated “metaphor center”?
Jason is a patient at a rehabilitation center in San Diego. He has been in a semicomatose state called akinetic mutism for several months before he is seen by my colleague Dr. Subramaniam Sriram. Jason is bedridden, unable to walk, recognize, or interact with people—not even his parents—even though he is fully alert and often follows people around with his eyes. Yet if his father goes next door and phones him, Jason instantly becomes fully conscious, recognizes his dad, and converses with him. When his father returns to the room, Jason reverts at once to a zombie-like state. It is as if there are two Jasons trapped inside one body: the one connected to vision, who is alert but not conscious, and the one connected to hearing who is alert and conscious. What might these eerie comings and goings of conscious personhood reveal about how the brain generates self-awareness?