Gazzaniga is the director of the SAGE Center for the Study of the Mind at the University of California, Santa Barbara, the director of the Law and Neuroscience Project funded by the MacArthur Foundation, and the president of the Cognitive Neuroscience Institute. In his studies of “split-brain” patients (initiated under the direction of Roger Sperry), whose corpus callosum has been cut to prevent epileptic fits, Gazzaniga discovered an essential asymmetry between human brain hemispheres. Information from the right hemisphere, about the left visual field and somatosensory signals from the left side of the body, is no longer transmitted to the left hemisphere. It does not reach the language capabilities of the left brain, where the conscious mind generates the explanations and reasons for its actions, generally after the fact. The mind is not conscious of information it does not receive, leading Gazzaniga to a theory of consciousness backed by the latest research in neuroscience.

In his 2005 book, The Ethical Brain, Gazzaniga devoted a chapter to what he calls "those old chestnuts - free will and personal responsibility." He says

The logic goes like this: The brain determines the mind, and the brain is a physical entity, subject to ail the rules of the physical world. The physical world is determined, so our brains must also be determined. If our brains are determined, and the brain is the necessary and sufficient organ that enables the mind, we are then left with these questions: Are the thoughts that arise from our mind also determined? Is the free will we seem to experience just an illusion? And if free will is an illusion, must we revise our concepts of what it means to be personally responsible for our actions?

Neuroscience [also] tells us that by the time any of us consciously experience something, the brain has already done its work. When we become consciously aware of making a decision, the brain has already made it happen. This raises the question, Are we out of the loop? It is one thing to worry about diminished responsibility due to insanity or brain disease, but now the normal person appears to be on the deterministic book as well. Should we abandon the concept of personal responsibility? I don't think so. We need to distinguish among brains, minds, and personhood. People are free and therefore responsible for their actions; brains are not responsible. (pp.88-89)

Philosophers have long debated the nature and existence of free will, a seemingly essential concept if we are to hold and value the idea of personal responsibility. Without getting into the academic details of these views, there are two primary and opposing views: that we have free will, and that we don't.

Gazzaniga mistakenly says that indeterminists are metaphysicians

Those who believe in free will (indeterminists) believe that some x factor — whether it's the "ghost in the machine," the soul, the mind, or the spirit — allows us to make choices and determine our actions and even our destiny by acting upon and changing the physical world and our path in it.

He does not acknowledge those determinists who are compatibilists

Those who don't accept free will (determinists) believe we live in a predetermined world — whether it's caused by fate, preordination, or genetic hard-wiring — where every action, human and otherwise, is inevitable.

In the rational world of science, the question arises, If determinism is true, what does the determining? Traditionally, genes have been implicated as the predictors of our destiny. Stephen Jay Gould, by no means an advocate for the idea of genetic determinism, explained the theory by stating that "if we are programmed to be what we are [by our genes] then [our] traits are ineluctable. We may, at best, channel them, but we cannot change them either by will, education or culture." Some processes are largely determined by our genes, but many of our traits are not entirely encoded in our genes. Our environment and chance also play a role in determining our traits and behaviors.

While genes build our brains, it is our brains, actively making millions of decisions per second, that ultimately enable our cognition and behavior. So it would seem that if we are to look at the issue of free will today, the brain is the place to look. Is the brain a deterministic organ, genetically hard-wired to carry out actions over which we have no control? Or is the brain — the home to the mind, the ghost in the machine — something capable of free will? (pp.90-91)

In his recent book, Who’s In Charge? Free Will and the Science of the Brain, Gazzaniga’s clear prose style and frequent humor make for easy reading, but a fuller understanding of the neuroscience requires more than just text. The book has only one illustration. It needs many more to explain Gazzaniga’s split-brain experiments. Fortunately, in his 2009 Gifford Lectures (Lecture 1, Lecture 2, Lecture 3, Lecture 4, Lecture 5, Lecture 6), Gazzaniga reviews the extraordinary discoveries of neuroscience that explain the mind as something embodied in the brain, but also as software to the brain’s hardware, a kind of abstract non-physical information that is nevertheless capable of exerting “downward causation” on the physical world.

Gazzaniga’s research found that the right hemisphere of the brain is poor at making inferences, similar to the whole brain of children younger than four years and the primates. On the other side, the developed human left hemisphere excels at inferences, constantly searching for patterns that can “make sense” of what is going on, bringing order out of chaos, and giving us answers to “why?” questions by discovering causes behind phenomena. Gazzaniga calls this our “Interpreter Module,” which “continually explains the world using the inputs it has from the current cognitive state and cues from the surroundings.” This ability to articulate stories that explains what is going on Gazzaniga describes as a “phase shift” between humans and other animals.

In his split-brain studies, Gazzaniga showed that the right brain is “conscious” of things going on in the left visual field. Consciousness is thus a local phenomenon, he says, indeed happening in many places, but the Interpreter is only conscious of the information that it receives. A lesion somewhere along the optic nerve or in the primary visual cortex leaves the patient “conscious” of a blind spot. A lesion in the visual associative cortex, however, leaves the patient unconscious of the blind spot. Consciousness is then the result of a constellation of local processes, information from which must reach the Interpreter in the left brain if it is show up in the narrative the Interpreter is generating.

William James said that we focus our attention on one of the myriad of sensations in the “blooming, buzzing confusion” of our unconscious, and this one sensation or thought bubbles up into our “stream of consciousness.” In Bernard Baars’ Global Workspace Theory, there is an executive function on the stage in a “Theater of Consciousness” selectively paying attention to untold numbers of audience members shouting to be heard. Michael Gazzaniga has developed neurophysical evidence for these profound ideas.

Gazzaniga found that his Interpreter can go overboard in its attempts to find patterns and causes. Trying to bring order out of chaos, it continues to search for a pattern where none exist. When presented with lights flashing 80 percent of the time above a line and 20 percent below, animals (and our right brains) will maximize their outcomes by always guessing above the line. But the Interpreter does “frequency matching,” guessing above 80 percent and below 20 percent of the time, for a 64 percent success rate. This obviously non-adaptive behavior evolved, says Gazzaniga, because it made our species more tenacious and more successful at developing theories about how the world works.

This discovery may explain the tendency of many scientists and most philosophers to explain away randomness as a positive contributing factor in the workings of the mind. William James said that both soft and hard determinists (like Gazzaniga) have an “antipathy to chance.”

“Physical laws govern the physical world. We are part of the physical world. Therefore, there are physical laws that govern our behavior. Determinism reigns. Einstein and Spinoza bought it. Who are we to question it?,” asks Gazzaniga. His answer? All the spectacular advances in science leave him with what he calls “one unshakeable fact. We are personally responsible agents and are to be held accountable for our actions, even though we live in a determined universe.” [His italics].

Gazzaniga knows that quantum physics introduces some irreducible indeterminism at the atomic and molecular level. This means you are free to choose Boston cream pie over berries for dessert, he says, and the choice was not determined at the very instant of the big bang. But he doubts whether quantum events in the brain help to make the choice free. “What on earth do humans want to be free from?,” he asks, “Indeed, what does free will even mean? However actions are caused, we want them to be carried out with accuracy, consistency, and purpose. When we reach for a glass of water, we don’t want our hand suddenly rubbing our eye.“ The short answer is that we do not want our actions to be predetermined, (by genetic factors) from the remote past before we were born, or (by environmental factors) from our life experiences, or (by causal chains) from the physical conditions that exist immediately before we deliberate about our decisions.

And moreover, as Gazzaniga says, we want our actions to be caused (determined) by our purposes and motives, our desires and feelings. Can we have it both ways? Yes, if the causality involved is only statistical, if the determinism is only adequate to explain the regularity of macroscopic physical laws. Quantum physics corresponds perfectly to classical physics in the limit of large numbers of atoms, and in the limit of large quantum numbers. In my two-stage model of free will, a limited indeterminism in the first stage can generate creative new ideas for consideration by an adequately determined second stage making the decision. The model is analogous to biological evolution, where microscopic stochasticity generating mutations in the gene pool is a creative force. This is the first step in a two-step process, as Ernst Mayr described it. The macroscopic second step of natural selection is an adequately determined process.

How does Gazzaniga defend the philosophically difficult proposition that immaterial ideas in an emergent mind can constrain the physical world? Can he solve the great problem of mind-body dualism? In his Gifford lectures, Gazzaniga proposes something analogous to the controversial Baldwin effect in evolutionary theory, the notion that learned behaviors transmitted culturally can so modify the environment that selection pressures now favor random mutations that have more reproductive success in the now changed environment. This creates a feedback loop called genetic assimilation when the new environment gets reflected in the genes, or niche construction when humans adapt the environment (as opposed to animals, who adapt to the environment). Gazzaniga proposes a similar feedback process in the mind-brain, where top-level mental ideas exert “downward causation” on the brain, biasing its decisions that are being made from the bottom (the neurons) up. Terrence Deacon makes similar arguments, the mind puts constraints on the physical world to further its goals. These two thinkers are onto something very important, in my opinion.

Finally, Gazzaniga thinks he has solved the problem of free will by noting that moral responsibility is not something that is created in brains, but in social interactions. He is right, of course. Morality is primarily a social and cultural question, despite many studies finding altruistic behavior in some animals. For decades, compatibilist philosophers have tried to identify free will with moral responsibility. That the two issues are connected historically is undeniable, but I disagree that “social interactions make us free to choose,” as Gazzaniga claims. The question of whether deterministic physical laws pre-determine all our actions is a physical and biological question. We may not have metaphysical free will, but we do have a biophysical free will. As William James insisted, some irreducible ontological chance must be part of the solution.