Consciousness and the Social Brain

1
The Magic Trick

    I was in the audience watching a magic show. Per protocol a lady was standing in a tall wooden box, her smiling head sticking out of the top, while the magician stabbed swords through the middle.
    A man sitting next to me whispered to his son, “Jimmy, how do you think they do
that
?”
    The boy must have been about six or seven. Refusing to be impressed, he hissed back, “It’s
obvious
, Dad.”
    “Really?” his father said. “You figured it out? What’s the trick?”
    “The magician makes it happen that way,” the boy said.
    The magician makes it happen. That explanation, as charmingly vacuous as it sounds, could stand as a fair summary of almost every theory, religious or scientific, that has been put forward to explain human consciousness.
    What is consciousness? What is the essence of awareness, the spark that makes us
us
? Something lovely apparently buried inside us is aware of ourselves and of our world. Without that awareness, zombie-like, we would presumably have no basis for curiosity, no realization that there is a world about which to be curious, no impetus to seek insight, whether emotional, artistic, religious, or scientific. Consciousness is the window through which we
understand
.
    The human brain contains about one hundred billion interacting neurons. Neuroscientists know, at least in general, how thatnetwork of neurons can compute information. But how does a brain become
aware
of information? What is sentience itself? In this book I propose a novel scientific theory of what consciousness might be and how a brain might construct it. In this first chapter I briefly sketch the history of ideas on the brain basis of consciousness and how the new proposal might fit into the larger context.
    The first known scientific account relating consciousness to the brain dates back to Hippocrates in the fifth century B.C . 1 At that time, there was no formal science as it is recognized today. Hippocrates was nonetheless an acute medical observer and noticed that people with brain damage tended to lose their mental abilities. He realized that mind is something created by the brain and that it dies piece by piece as the brain dies. A passage attributed to him summarizes his view elegantly:

Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears. Through it, in particular, we think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant. 1

    The importance of Hippocrates’s insight that the brain is the source of the mind cannot be overstated. It launched two and a half thousand years of neuroscience. As a specific explanation of consciousness, however, one has to admit that the Hippocratic account is not very helpful. Rather than explain consciousness, the account merely points to a magician. The brain makes it happen. How the brain does it, and what exactly consciousness may be, Hippocrates left unaddressed. Such questions went beyond the scope of his medical observations.
    Two thousand years after Hippocrates, in 1641, Descartes 2 proposed a second influential view of the brain basis of consciousness. In Descartes’s view, the mind was made out of an ethereal substance, a fluid, that was stored in a receptacle in the brain. He called the fluid
res cogitans
. Mental substance. When he dissected the brain looking for the receptacle of the soul, he noticed that almost every brain structurecame in pairs, one on each side. In his view, the human soul was a single, unified entity, and therefore it could not possibly be divided up and stored in two places. In the end he found a small single lump at the center of the brain, the pineal body, and deduced that it must be the house of the soul. The pineal body is now known to be a gland that produces melatonin and has nothing whatsoever to do with a soul.
    Descartes’ idea, though refreshingly clever for the time, and though influential in philosophy and theology, did not advance the scientific understanding of consciousness. Instead of proposing an explanation of consciousness, he attributed consciousness to a magic fluid. By what mechanism a fluid substance can cause the experience of consciousness, or where the fluid itself comes from, Descartes left unexplained—truly a case of pointing to a magician instead of explaining the trick.
    One of the foundation bricks of modern science,