The Economist believes that “modern neuroscience is eroding the idea of free will”:
In the late 1990s a previously blameless American began collecting child pornography and propositioning children. On the day before he was due to be sentenced to prison for his crimes, he had his brain scanned. He had a tumour. When it had been removed, his paedophilic tendencies went away. When it started growing back, they returned. When the regrowth was removed, they vanished again. Who then was the child abuser?
His case dramatically illustrates the challenge that modern neuroscience is beginning to pose to the idea of free will. The instinct of the reasonable observer is that organic changes of this sort somehow absolve the sufferer of the responsibility that would accrue to a child abuser whose paedophilia was congenital. But why? The chances are that the latter tendency is just as traceable to brain mechanics as the former; it is merely that no one has yet looked. Scientists have looked at anger and violence, though, and discovered genetic variations, expressed as concentrations of a particular messenger molecule in the brain, that are both congenital and predisposing to a violent temper. Where is free will in this case?
While this example of a tumor in the orbitofrontal cortex is certainly fascinating, I disagree with the philosophical implications that The Economist draws from it. While there certainly are diseases of the brain that are deterministic in nature – no amount of “free will” can cure you of schizophrenia, or Huntington’s, or ALS – we should also not assume that every brain disease is equally deterministic. There are two main reasons why I’m not ready to give up on free will.
The first reason is plasticity. One of the great themes of modern neuroscience is the malleability of the mind. While a genetic program specifies the gross anatomy of our brain, the all important details are determined by experience. In fact, the best metaphor for the mind might be our immune system. Just as our antibodies are constantly altered in response to the pathogens we actually encounter (we do not have the B-cells of our parents, or of our identical twin), the brain is constantly adapting to the particular conditions of our own life. This is why blind people can use their visual cortex to read Braille, and why the deaf can process sign language in their auditory cortex. Lose a finger and, thanks to neural plasticity, your other fingers will take over its brain space. In one particularly audacious experiment, the neuroscientist Mriganka Sur literally re-wired the mind of a ferret, so that the information from its retina was plugged into its auditory cortex. To Sur’s astonishment, the ferrets could still see. Furthermore, their auditory cortex now resembled the typical ferret visual cortex, complete with spatial maps and neurons tuned to detect slants of light. Michael Merzenich, one of the founders of the plasticity field, called this experiment “The most compelling demonstration you could have that experience shapes the brain.”
An important discovery closely related to plasticity has been the discovery of neurogenesis. I’ve spilled a lot of ink elsewhere on this phenomenon, but it’s important to remember that your brain is constantly generating new neurons. The brain, far from being fixed, is actually in a constant state of cellular upheaval.
The second reason I’m not convinced that freedom is nothing but an illusion is the amount of randomness (or stochasticity) inherent in living organisms. Fruit flies, for example, have long hairs on their body that serve as sensory organs. The location and density of those hairs differ between the two sides of the fly, but not in any systematic way. After all, the two sides of the fly are encoded for by the same genes and have developed in the same environment. Instead, the variation in the fly is a consequence of random atomic jostling inside its cells, what biologists call “developmental noise.” (This is also why our left and right hands have different fingerprints.)
This same principle is even at work in our brain. Neuroscientist Fred Gage has found that retrotransposons–junk genes which randomly jump around our genome–are present at unusually high numbers in neurons. In fact, these troublemaking scraps of DNA insert themselves into almost 80 percent of our brain cells, arbitrarily altering their genetic program. At first, Gage was befuddled by this data. The brain seemed intentionally destructive, bent on dismantling its own precise instructions. But then Gage had an epiphany. He realized that all these genetic interruptions created a population of perfectly unique minds, since each brain suffered from retrotransposons in its own way. In other words, cellular chaos creates our individuality. Gage’s new hypothesis is that all this mental anarchy is adaptive, as it allows our genes to generate minds of almost infinite diversity.
Like the discovery of neurogenesis and neural plasticity, the discovery that biology thrives on disorder is paradigm shifting. The more science knows about life’s intricacies, about how DNA actually becomes protein and about how proteins actually become us, the less life resembles a finely honed Swiss clock. Chaos is everywhere. As Karl Popper once said, life is not a clock, it is a cloud. Like a cloud, life is “highly irregular, disorderly, and more or less unpredictable.” Clouds, carried and crafted by an infinity of currents, have inscrutable wills; they seethe and tumble in the air, and are a little different with every moment in time. We are the same way. As has happened so many times before in the history of science, the idÃ©e fixe of deterministic order proved to be a mirage.
This is why I’m not sorry worried about free will being erased by the facts of biology. Neuroscience hasn’t discovered that our mind is nothing but a genetic machine. Far from it. In fact, the most profound discoveries of modern neuroscience have focused on all the ways our mind is not determinstic. Of course, much of this indeterminacy is simply randomness, the stochastic flutter of our cellular machinery. For lack of a better term, I’ll call this negative freedom. But a significant part of our freedom is also positive: we are also beginning to understand all the ways the structure of our brain responds to our personal, individual experiences. Free will is here to say. As usual William James said it best, “My first act of free will shall be to believe in free will.”
[Thanks for the tip Steve!]