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. When it had been removed, his paedophilic tendencies went away. When the regrowth was removed, they vanished again. His case dramatically illustrates the challenge that modern neuroscience is beginning to pose to the idea of free will.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.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.There are two main reasons why I’m not ready to give up on free will. 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.
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. 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. 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.