The following is an excerpt from the new book Consciousness and the Social Brain by Michael S. A. Graziano (Oxford University Press, 2015):

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 that network of neurons can compute information. But how does a brain become aware of information? What is sentience itself?

The first known scientific account relating consciousness to the brain dates back to Hippocrates in the fifth century b.c. 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."

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 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 rescogitans. Mental substance. When he dissected the brain looking for the receptacle of the soul, he noticed that almost every brain structure came 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, especially modern psychology, is a brilliant treatise so heft y that it is literally rather brick-like, Kant’s A Critique of Pure Reason, published in 1781. In Kant’s account, the mind relies on what he termed “a priori forms,” abilities and ideas within us that are present first before all explanations and from which everything else follows. On the subject of consciousness, therefore, Kant had a clear answer: there is no explaining the magic. It is simply supplied to us by divine act. Quite literally, the magician did it.

Hippocrates, Descartes, and Kant represent only three particularly prominent accounts of the mind from the history of science. I could go on describing one famous account after the next and yet get no closer to insight. Even if we fast-forward to modern neuroscience and examine the many proposed theories of consciousness, almost all of them suffer from the same limitation. They are not truly explanatory theories. They point to a magician but do not explain the magic.

One of the first, groundbreaking neurobiological theories of consciousness was proposed in 1990 by the scientists Francis Crick (the co-discoverer of the structure of DNA) and Christof Koch. They suggested that when the electrical signals in the brain oscillate they cause consciousness. The idea goes something like this: the brain is composed of neurons that pass information among each other. Information is more efficiently linked from one neuron to another, and more efficiently maintained over short periods of time, if the electrical signals of neurons oscillate in synchrony. Therefore, consciousness might be caused by the electrical activity of many neurons oscillating together.

This theory has some plausibility. Maybe neuronal oscillations are a precondition for consciousness. But note that, once again, the hypothesis is not truly an explanation of consciousness. It identifies a magician. Like the Hippocratic account, “The brain does it” (which is probably true), or like Descartes’s account, “The magic fluid inside the brain does it” (which is probably false), this modern theory stipulates that “the oscillations in the brain do it.” We still don’t know how. Suppose that neuronal oscillations do actually enhance the reliability of information processing. That is impressive and on recent evidence apparently likely to be true. But by what logic does that enhanced information processing cause the inner experience? Why an inner feeling? Why should information in the brain—no matter how much its signal strength is boosted, improved, maintained, or integrated from brain site to brain site—become associated with any subjective experience at all? Why is it not just information without the add-on of awareness?

For this type of reason, many thinkers are pessimistic about ever finding an explanation of consciousness. The philosopher Chalmers, in 1995, put it in a way that has become particularly popular. He suggested that the challenge of explaining consciousness can be divided into two problems. One, the easy problem, is to explain how the brain computes and stores information. Calling this problem easy is, of course, a euphemism. What is meant is something more like the technically possible problem given a lot of scientific work. In contrast, the hard problem is to explain how we become aware of all that stuff going on in the brain. Awareness itself, the essence of awareness, because it is presumed to be nonphysical, because it is by definition private, seems to be scientifically unapproachable. Again, calling it the hard problem is a euphemism; it is the impossible problem. We have no choice but to accept it as a mystery. In the hard-problem view, rather than try to explain consciousness, we should marvel at its insolubility.

The hard-problem view has a pinch of defeatism in it. I suspect that for some people it also has a pinch of religiosity. It is a keep-your- scientific-hands-off-my-mystery perspective. One conceptual difficulty with the hard-problem view is that it argues against any explanation of consciousness without knowing what explanations might arise. It is difficult to make a cogent argument against the unknown. Perhaps an explanation exists such that, once we see what it is, once we understand it, we will find that it makes sense and accounts for consciousness.

The current scientific study of consciousness reminds me in many ways of the scientific blind alleys in understanding biological evolution. Charles Darwin published his book The Origin of Species in 1859, but long before Darwin, naturalists had already suspected that one species of animal could evolve into another and that different species might be related in a family tree. The idea of a family tree was articulated a century before Darwin, by Linnaeus, in 1758. What was missing, however, was the trick. How was it done? How did various species change over time to become different from each other and to become sophisticated at doing what they needed to do? Scholars explored a few conceptual blind alleys, but a plausible explanation could not be found. Since nobody could think of a mechanistic explanation, since a mechanistic explanation was outside the realm of human imagination, since the richness and complexity of life was obviously too magical for a mundane account, a deity had to be responsible. The magician made it happen. One should accept the grand mystery and not try too hard to explain it.

Then Darwin discovered the trick. A living thing has many offspring; the offspring vary randomly among each other; and the natural environment, being a harsh place, allows only a select few of those offspring to procreate, passing on their winning attributes to future generations. Over geological expanses of time, increment by increment, species can undergo extreme changes. Evolution by natural selection. Once you see the trick behind the magic, the insight is so simple as to be either distressing or marvelous, depending on your mood. As Huxley famously put it in a letter to Darwin, “How stupid of me not to have thought of that!”

The neuroscience of consciousness is, one could say, pre-Darwinian. We are pretty sure the brain does it, but the trick is unknown. Will science find a workable theory of the phenomenon of consciousness?

I propose a theory of consciousness that I hope is unlike most previous theories. This one does not merely point to a magician. It does not merely point to a brain structure or to a brain process and claim without further explanation, ergo consciousness. Although I do point to specific brain areas, and although I do point to a specific category of information processed in a specific manner, I also attempt to explain the trick itself. What I am trying to articulate is not just, “Here’s the magician that does it,” but also, “Here’s how the magician does it.”

For more than twenty years I studied how vision and touch and hearing are combined in the brain and how that information might be used to coordinate the movement of the limbs. I summarized much of that work in a previous book, The Intelligent Movement Machine, in 2008. These scientific issues may seem far from the topic of consciousness, but over the years I began to realize that basic insights about the brain, about sensory processing and movement control, provided a potential answer to the question of consciousness.

The brain does two things that are of particular importance to the present theory. First, the brain uses a method that most neuroscientists call attention. Lacking the resources to process everything at the same time, the brain focuses its processing on a very few items at any one time. Attention is a data-handling trick for deeply processing some information at the expense of most information. Second, the brain uses internal data to construct simplified, schematic models of objects and events in the world. Those models can be used to make predictions, try out simulations, and plan actions.

What happens when the brain inevitably combines those two talents? In theory, awareness is the brain’s simplified, schematic model of the complicated, data-handling process of attention. Moreover, a brain can use the construct of awareness to model its own attentional state or to model someone else’s attentional state. For example, Harry might be focusing his attention on a coffee stain on his shirt. You look at him and understand that Harry is aware of the stain. In the theory, much of the same machinery, the same brain regions and computational processing that are used in a social context to attribute awareness to someone else, are also used on a continuous basis to construct your own awareness and attribute it to yourself. Social perception and awareness share a substrate. The attention schema theory, as I eventually called it, takes a shot at explaining consciousness in a scientifically plausible manner without trivializing the problem.

The theory took rough shape in my mind (in my consciousness, let’s say) over a period of about 10 years.

A great many reaction pieces were published by experts on the topic of mind and consciousness and a great many more unpublished commentaries were communicated to me. Many of the commentaries were enthusiastic, some were cautious, and a few were in direct opposition. I am grateful for the feedback, which helped me to further shape the ideas and their presentation. It is always difficult to communicate a new idea. It can take years for the scientific community to figure out what you are talking about, and just as many years for you to figure out how best to articulate the idea.

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None of us knows for certain how the brain produces consciousness, but the attention schema theory looks promising. It explains the main phenomena. It is logical, conceptually simple, testable, and already has support from a range of previous experiments. I do not put the theory in opposition to the three or four other major neuroscientific views of consciousness. Rather, my approach fuses many previous theories and lines of thought, building a single conceptual framework, combining strengths. For all of these reasons, I am enthusiastic about the theory as a biological explanation of the mind—of consciousness itself—and I am eager to communicate the theory properly.