The Tell-Tale Brain

recently, in experimental science (by Galileo)—the behavior of a modern civilized person is vastly more complex than that of humans ten thousand to fifty thousand years ago.

This second leap forward in culture was even more dramatic than the first. There is a greater behavioral gap between pre–and post–500 B.C.E. humans than between, say, Homo erectus and early Homo sapiens. Our Martian scientist might conclude that a new set of mutations made this possible. Yet given the time scale, that’s just not possible. The revolution stemmed from a set of purely environmental factors which happened fortuitously at the same time. (Let’s not forget the invention of the printing press, which allowed the extraordinary spread and near universal availability of knowledge that usually remained confined to the elite.) But if we admit this, then why doesn’t the same argument apply to the first great leap? Maybe there was a lucky set of environmental circumstances and a few accidental inventions by a gifted few which could tap into a preexisting ability to learn and propagate information quickly—the basis of culture. And in case you haven’t guessed by now, that ability might hinge on a sophisticated mirror-neuron system.

A caveat is in order. I am not arguing that mirror neurons are sufficient for the great leap or for culture in general. I’m only saying that they played a crucial role. Someone has to discover or invent something—like noticing the spark when two rocks are struck together—before the discovery can spread. My argument is that even if such accidental innovations were hit upon by chance by individual early hominins, they would have fizzled out were it not for a sophisticated mirror-neuron system. After all, even monkeys have mirror neurons, but they are not bearers of a proud culture. Their mirror-neuron system is either not advanced enough or is not adequately connected to other brain structures to allow the rapid propagation of culture. Furthermore, once the propagation mechanism was in place, it would have exerted selective pressure to make some outliers in the population more innovative. This is because innovations would only be valuable if they spread rapidly. In this respect, we could say mirror neurons served the same role in early hominin evolution as the Internet, Wikipedia, and blogging do today. Once the cascade was set in motion, there was no turning back from the path to humanity.

CHAPTER 5

  Where Is Steven? The Riddle of Autism

You must always be puzzled by mental illness. The thing I would dread most, if I became mentally ill, would be your adopting a common sense attitude; that you could take it for granted that I was deluded.

—LUDWIG WITTGENSTEIN

“I KNOW STEVEN IS TRAPPED IN THERE SOMEWHERE, DR. RAMACHANDRAN. If only you could find a way to tell our son how dearly we love him, perhaps you could bring him out.”

How often have physicians heard that heartbreaking lament from parents of children with autism? This devastating developmental disorder was discovered independently by two physicians, Leo Kanner in Baltimore and Hans Asperger in Vienna, in the 1940s. Neither doctor had any knowledge of the other, and yet by an uncanny coincidence they gave the syndrome the same name: autism. The word comes from the Greek autos meaning “self,” a perfect description because the most striking feature of autism is a complete withdrawal from the social world and a marked reluctance or inability to interact with people.

Take Steven, for instance. He is six years old, with freckled cheeks and sandy-brown hair. He is sitting at a play table drawing pictures, his brow lightly furrowed in concentration. He is producing some beautiful drawings of animals. There’s one of a galloping horse that is so wonderfully animated that it seems to leap out of the paper. You might be tempted to walk over and praise him for his talent. The possibility that he might be profoundly incapacitated would never cross your mind. But the moment you try to talk to him, you realize that there’s a sense in which Steven the person simply isn’t there. He is incapable of anything remotely resembling the two-way exchange of normal conversation. He refuses to make eye contact. Your attempts to engage him make him extremely anxious. He fidgets and rocks his body to and fro. All attempts to communicate with him meaningfully have been, and will be, in vain.

Since the time of Kanner and Asperger, there have been hundreds of case studies in the medical literature documenting, in detail, the various seemingly unrelated symptoms that characterize autism. These fall into two major groups: social-cognitive and sensorimotor. In the first group we have the single most important diagnostic symptom: mental aloneness and a lack of contact with the world, particularly the social world, as well as a profound inability to engage in normal conversation. Going hand in hand with this is an absence of emotional empathy for others. Even more surprising, autistic children express no outward sense of play, and they do not engage in the untrammeled make-believe with which normal children fill their waking hours. Humans, it has been pointed out, are the only animals that carry our sense of whimsy and playfulness into adulthood. How sad it must for parents to see their autistic sons and daughters impervious to the enchantment of childhood. Yet despite this social withdrawal, autistic children have a heightened interest in their inanimate surroundings, often to the point of being obsessive. This can lead to the emergence of odd, narrow preoccupations and a fascinations with things that seem utterly trivial to most of us, like memorizing all the phone numbers in a directory.

Let us turn now to the second cluster of symptoms: sensorimotor. On the sensory side, autistic children may find specific sensory stimuli highly distressing. Certain sounds, for example, can set off a violent temper tantrum. There is also a fear of novelty and change, and an obsessive insistence on sameness, routine, and monotony. The motor symptoms include a to-and-fro rocking of the body (such as we saw with Steven), repetitive hand movements including flapping motions and self-slapping, and sometimes elaborate, repetitive rituals. These sensorimotor symptoms are not quite as definitive or as devastating as the social-emotional ones, but they co-occur so frequently that they must be connected somehow. Our picture of what causes autism would be incomplete if we failed to account for them.

There is one more motor symptom to mention, one that I think holds the key to unraveling the mystery: Many autistic children have difficulty with miming and imitating other people’s actions. This simple observation suggested to me a deficiency in the mirror-neuron system. Much of the remainder of this chapter chronicles my pursuit of this hypothesis and the fruit it has borne so far.

Not surprisingly, there have been dozens of theories of what causes autism. These can be broadly divided into psychological explanations and physiological explanations—the latter emphasizing innate abnormalities in brain wiring or neurochemistry. One ingenious psychological explanation, put forward by Uta Frith of University College of London and Simon Baron-Cohen of Cambridge University, is the notion that children with autism have a deficient theory of other minds. Less credible is the psychodynamic view that blames bad parenting, an idea that is so absurd that I won’t consider it further.

We encountered the term “theory of mind” in passing in the previous chapter in relation to apes. Now let me explain it more fully. It is a technical term that is widely used in the cognitive sciences, from philosophy to primatology to clinical psychology. It refers to your ability to attribute intelligent mental beingness to other people: to understand that your fellow humans behave the way they do because (you assume) they have thoughts, emotions, ideas, and motivations of more or less the same kind as you yourself possess. In other words, even though you cannot actually feel what it is like to be another individual, you use your theory of mind to automatically project intentions, perceptions, and beliefs into the minds of others. In so doing you are able to infer their feelings