The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

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”?