Eliezer J. Sternberg is a neurologist at Yale-New Haven Hospital and the author of “NeuroLogic: The Brain’s Hidden Rationale Behind Our Irrational Behavior.”

Three decades after being awarded the Nobel Prize for his discovery of DNA, Francis Crick wrote a book about consciousness, “The Astonishing Hypothesis: The Scientific Search for the Soul.” It was momentous: A world-renowned scientist had decided to directly confront the mind/body problem, the centuries-old challenge of reconciling the brain, a gelatinous mass of physical tissue, and human consciousness, the realm of emotion, volition and boundless imagination. Crick’s contention that the human mind arises from neurons in the brain rather than from an ineffable soul is perhaps less astonishing today, when this premise is nearly universally accepted among neuroscientists. But it still hints at something remarkable about Crick’s own mind. Why would a Nobel-winning scientist, already credited with discovering the secret of life, decide to switch gears and focus on an inquiry not only in a different field but so scientifically impenetrable as to have earned nicknames like “the hard problem” and “the last great mystery of science?” Crick answered this question with “what I called the gossip test: What you’re really interested in is what you gossip about. Gossip is things you’re interested in, but you don’t know much about.” In short: genuine curiosity.

As one of the greatest neuroscientists living today, Michael S. Gazzaniga could have similarly rested on his laurels. He helped craft the modern understanding of the differences between the cerebral hemispheres. Though they appear anatomically identical, everyone now knows that the right and left brain empower us with different abilities. Much of this knowledge is thanks to the work Gazzaniga did in the 1960s with Roger Sperry on split-brain patients who had their cerebral hemispheres surgically disconnected, leading to, among other discoveries, the revelation that the two sides are able to function independently, like two autonomous minds.

Though split-brain research is closer to consciousness research than is genomics, coming up with a theory of consciousness would be the greatest challenge Gazzaniga ever faced. So why venture there? Why would an accomplished scientist expose himself to inevitable criticism, since the likelihood of success is so slim? Gazzaniga’s answer is reminiscent of Crick’s: “Nobody said the search was going to be easy. But . . . once bitten by the question we spend our lives gnawed by the desire for an answer.”

So, what is Gazzaniga’s answer to humanity’s greatest question? In the introduction to his new book, “The Consciousness Instinct,” Gazzaniga says that “plainly stated, I believe consciousness is an instinct.” It’s plainly stated, but what does it mean? An instinct, in my mind, is an innate, preprogrammed behavior pattern exhibited by animals, such as caterpillars building cocoons or baby kangaroos climbing into their mothers’ pouches to suckle. Does Gazzaniga mean consciousness is an innate, preprogrammed pattern of behavior? That of course depends on how he defines the word “instinct.” Some 225 pages after stating his thesis, just a few pages before the end of the book, he writes, “Let’s pause to ask the fundamental question: what is an instinct, anyway?”


“The Consciousness Instinct,” by Michael S. Gazzaniga (Farrar, Straus and Giroux)

The delay aside, Gazzaniga goes to the great psychologist William James for a definition: “The faculty of acting in such a way as to produce certain ends, without foresight of the ends, and without previous education in the performance. . . . [Instincts] are the functional correlatives of structure.” Gazzaniga says instincts are programs, the software that correlates to the intricate hardware of the brain. But that would seem to imply that consciousness, the essence of humanity, is as automatic and preprogrammed as the behavior of caterpillars building cocoons or joeys suckling. Not so, Gazzaniga says, because the low-level instincts that initiate simple behaviors are “sequenced in a coordinated fashion for more complex actions that make them look an awful lot like higher-order instincts.” This sequencing occurs through “competitive dynamics” as countless bubbles of low-level instincts try to burble their way up to the top level of brain processing, where the “top bubble ultimately bursts into an idea.” Gazzaniga postulates, “Consider that maybe, just maybe, consciousness can only be understood as the brain’s bubbles . . . [each] getting its moment.”

Basically, Gazzaniga says, the lower-level instincts can be thought of as individual people in society, each with a certain behavior and a vote. He says complex instincts are the “state of societal relationships . . . [the] democracies” that result. Consciousness emerges, therefore, from how those democracies vote. It is those results, generated by layers and layers of neuronal bureaucracy, that we experience as fear, desire, determination, reasoning and decision-making.

There’s an elegance to this model, but it isn’t new. The case was probably best stated by the late Nobel Prize-winning biologist Gerald Edelman, who argued that consciousness ultimately arises from low-level cellular competition, which he called “neural Darwinism.” The mind, Edelman said, is an “emergent property” of neural circuitry. While the individual cells and synapses are not themselves conscious, consciousness emerges through their interaction at the highest level of processing. Similarly, particles of hydrogen and oxygen are not liquid, but when combined as H2O, they attain new properties, and through the interactions of about a billion trillion water molecules, the property of liquidity emerges.

A version of the emergent property argument, Gazzaniga’s mental democracy ends up being more of a provocative thought exercise than a fleshed-out explanation. Between the introduction and conclusion of the book, you won’t find an account of the science of instincts, a detailing of how they might interact or a model of how that interaction might bring about consciousness. Instead, you’ll find an eloquent history of the scientific study of consciousness. Gazzaniga traces the field from its philosophical roots in the 17th century through the age of early empirical thinking, modern neuroscience and neurological case studies, and even into the realm of quantum physics. After each historical narrative, he discusses the way each field has broadly influenced the way he thinks about mind and brain.

What’s profound about Gazzaniga’s “The Consciousness Instinct” parallels what made Crick’s “Astonishing Hypothesis” so special: It is a window into the mind of one of the greats. It is a rare opportunity to watch a scientific champion grapple with perhaps our most formidable mystery, juggling multiple fields of study, laying out his thinking, though raw and incomplete, so others may continue the work. For the rest of us in the neurosciences, struggling merely to balance on the shoulders of giants, we can only be grateful when one of those giants nudges us forward, to continue soul-searching, by taking a bit of time to gossip with us.

The Consciousness Instinct
Unraveling the Mystery of How the Brain Makes the Mind

By Michael S. Gazzaniga

Farrar, Straus and Giroux. 274 pp. $28