Our freedom to choose, to make good or bad decisions about everything from which dessert to select to whether to save a life or commit a crime, seems part of our basic human nature. Long the province of philosophers and theologians, recently free will has become a question that fascinates neuroscientists. Looking for its basis in the brain has led some to argue that free will is only an illusion—a perception not congruent with the unconscious biochemical processes that they see as leading to thought and action. Two senior scientists, a neurologist and a psychiatrist, debate the meaning of free will and whether brain science can, now or ever, fully explain it. Each scientist first wrote a position statement; they then exchanged statements to write rejoinders.
Free Will: An Illusory Driver of Behavior
Mark Hallett’s opening statement
My position is that free will is only a perception—our interpretation of how we experience our actions in the world. No evidence can be found for the common view that it is a function of our brains that causes behavior. I will make my argument based on research about making “voluntary” movements for two reasons. First, I am a neurologist, specifically a motor physiologist. Second, movements are easily measured. While other, more complex decisions, such as what I choose for dinner, also can be viewed as influenced by free will, I suspect that they will turn out to be analogous to movement. Anyway, such decisions often eventually manifest in movement of some kind, perhaps reaching for the cookbook or a take-out menu.
I do not doubt that I feel strongly that I have freedom of choice. And I suspect most humans have the same feeling as I do, even though I can’t assess this directly. But, of course, this feeling of free will is the case only when I think about it, since most of the time I just go about my business, more or less on automatic pilot. My feeling that I have free will is a subjective perception, an element of my consciousness that philosophers call a “quale.” We do not understand The answers to these questions are easy only for the dualist, who believes in a mind separate from the brain and who thinks that free will comes from the mind. No evidence for this position can be found, however, and therefore most scientists reject it. the biological nature of consciousness or how awareness is generated, so it is difficult to understand the physiology of any quale, including the perception of free choice. But we do know that our sense of the world is a product of our brain and that a one-to-one match between reality and that interpretation does not exist. Our introspection, our sense of what our brain is doing—while clearly useful to us and also valuable as an object of study—can be deceptive.
Looking for Free Will in the Brain
We are constantly making movements. While we certainly think we choose them freely, do we really? What would it mean if we did? The physiology of movement has been the object of intense study by scientists, and we now know the drivers of movement. These drivers include sensory input from the external world, our emotions, our biological drive for homeostasis—for balance of our physiological systems—and our past experience, including rewards and punishments that resulted from previous actions. Do these fully determine our choice or can we identify another factor, which we call free will?
The answers to these questions are easy only for the dualist, who believes in a mind separate from the brain and who thinks that free will comes from the mind. No evidence for this position can be found, however, and therefore most scientists reject it. The mind (consciousness) is a product of the brain, so if free will can be a driver of movement, we have to be able to find it in the brain. All the tools of modern neuroscience provide ways of studying this question.
Looking for free will in the brain not only is interesting for its own sake, but it is also important for understanding a number of neurological and psychiatric conditions.1 We can observe in patients with certain disorders that a relationship between movement genesis and a sense of volition is not mandatory. For example, people with Tourette syndrome often say that they cannot not act out their tics. With psychogenic movement disorders—also called conversion disorders or the old term, hysteria—the movements look voluntary, but patients say they are involuntary. In schizophrenia, movements also may look normal, but patients might say that these movements are controlled by external agents. In early Huntington’s disease, the apparently involuntary chorea (rapid jerky movement) is sometimes interpreted as being voluntary. And in anosognosia (a condition in which a person who suffers disability due to brain injury seems unaware of an impairment), patients may think that they have made a movement when they have not.
Do We Freely Choose to Move?
In general, scientists need to study what we call “simplified preparations” in which it is possible to control all the variables in a situation. One such experimental situation is making a single movement of the hand or finger. People can be asked to move whenever they want to; the commonsense view is that a person consciously decides to make a movement and then makes it. Free choice has preceded the movement.