Last month, the case against Patrizia Reggiani was reopened in Italy. She is serving a 26-year jail sentence for having ordered the killing of her husband, the fashion supremo Maurizio Gucci. At the first trial in 1998, expert witnesses dismissed her lawyers' claims that surgery for a brain tumour had changed her personality. The new trial has been granted because her lawyers believe that brain imaging techniques developed since then will reveal damage that was previously undetectable, and strengthen their case for an acquittal.
The idea that someone should not be punished if their abnormal neural make-up leaves them no choice but to break the law is contentious but not new. However, one prominent neuroscientist has sparked a storm by picking it up and turning it round. Writing in the Frankfurter Allgemeine Zeitung, one of Germany's leading newspapers, Wolf Singer argued that crime itself should be taken as evidence of brain abnormality, even if no abnormality can be found, and criminals treated as incapable of having acted otherwise.
His claims have brought howls of outrage from academics across the sciences and humanities. But Singer counters that the idea is nothing but a natural extension of the thesis that free will is an illusion - a theory that he feels is supported by decades of work in neuroscience.
The head of the Max Planck Institute for Brain Research in Frankfurt, Singer is best known for his work on the so-called binding problem of perception. This is the conundrum of how we perceive an object as an integrated whole, when we know that the brain processes the various elements of it - colours, angles, and so on - separately. His group was among the first to suggest, and then demonstrate, that the answer lay in the synchronisation encoding the separate features. He has since extrapolated those ideas to the process by which we make decisions, which has led him to question whether we are really the free-acting agents we imagine ourselves to be.
His argument goes like this. Neurobiology tells us that there is no centre in the brain where actions are planned and decisions made. Decisions emerge from a collection of dynamic systems that run in parallel and are underpinned by nerve cells that talk to each other - the brain. If you look back in evolution to say, the sea slug Aplysia, you see that the building blocks of this brain have not changed. The amino acids, the nerve cells, the signalling pathways and largely the genes, are the same. "It's the same material [in humans], just more complex," says Singer. "So the same rules must govern what humans do. Unavoidable conclusion."
He argues that the human brain has to be complex to compute all the myriad variables that influence each decision we make - genetic factors, socially learned factors, momentary triggers including commands and wishes, to name a few. And because it considers most of those variables at a subconscious level, we are not aware of all the factors that make us behave in a certain way, just as we are not aware of all the elements of an object that are processed separately by our visual brains. As humans, however, we are able to extract some of those factors and make them the focus of attention; that is, render them conscious. And with our behaviour, as with the world we see, we yearn to build a coherent picture. So we might justify our decisions in ways that have nothing to do with our real, subconscious motivations.
The most striking example of this is hypnotism. Singer himself learned how to hypnotise while a student at Cambridge University. At a party, he instructed a Royal Air Force pilot to remove the bulb from a light fitting and place it in a flowerpot, on hearing the word Germany. The pilot did so in mid-conversation, much to the amusement of the onlookers. They were amateurs, they didn't debrief him properly. And when they told him what he had done, because he had no recollection of doing it, he was extremely disturbed.
According to Singer, what the pilot did is explained by the structure of his brain and its inherent weakness, if you see it as a weakness to be susceptible to hypnotism. The same goes for a murderer or a thief, he says. We live in a society where people whose behaviour is considered to deviate from the norm - as determined arbitrarily by that society - answer to the justice system. But the way they are treated by that system is, he believes, inconsistent.
If some abnormality is found in a person's brain, the doctor's report is submitted as mitigating evidence and the defendant may be treated more leniently. If nothing is discovered, they are not. Take the case of the British man who terrorised 200 officials because he thought they intended to have him sectioned under the Mental Health Act. Psychiatrists found no sign of a mitigating mental illness, and he was jailed for life. But, says Singer, if a person does something antisocial, the reason for it is in the brain. The underlying cause may be a twist in a gene, or a tiny hormonal imbalance that cannot be detected with current technology. "It could have multiple reasons," he says. "But these reasons must all manifest themselves in brain architecture."
In practice, he says, the change in thinking he advocates wouldn't change the way we treat criminals all that much. People considered a danger to society should be kept away from society, re-educated as far as possible and in cases where this is not possible, simply kept away, as they already are. But he would like to see the courts place less burden on psychiatrists, who are not capable of identifying all the subtle structural changes that lead individuals to behave as they do. "As long as we can't identify all the causes, which we cannot and will probably never be able to do, we should grant that for everybody there is a neurobiological reason for being abnormal," he says.
He does not argue that a criminal should not be held responsible for their crime. After all, if a person is not responsible for their own brain, who is? Neither does he argue that we should do away with concepts of good and evil. "We judge our fellow men as either conforming to our rules or breaking them," he says. "We need to continue to assign values to our behaviour, because there is no other way to organise society." However, he does argue that when people commit crimes, they are not acting independently of the nerve cells and amino acids that make up their brains, and that behave according to certain deterministic principles.
One important implication of his argument is that treatment meted out to offenders should be less about revenge and punishment, and more about assessing their risk of re-offending, given the brain they have. Of course, this already happens. If a woman has been driven to a crime of passion after severe provocation, having otherwise lived an exemplary life, she is considered less of a danger to society than a man who has frequently abducted teenage girls, raped and murdered them. Another corollary of Singer's ideas that he recognises will be harder for people to swallow, is that the consequences of a crime should be considered less important than they are, since an individual can only control his own actions and not those of others. For example, a driver seen running a red light should be treated the same way whether or not he hit the child who, unseen from the wheel, stepped into the road at the same moment.
"Breathtaking," is how Ted Honderich, a philosopher at University College London, scathingly describes Singer's foray into traditional philosophical territory. Honderich says philosophers have discussed different definitions of freedom for centuries, one of which is perfectly compatible with the sort of determinism Singer describes. That is, if free action is defined as action caused by your character - whatever hereditary and environmental influences contributed to that character - then you are free even if your brain does resemble that of a slug.
And although the discussion might appear to have degenerated into a slanging match between scientists and philosophers, neuroscientists have also criticised Singer. "We don't know enough to make such conclusions," says Cornelius Weiller, an expert in brain imaging at Hamburg University. Singer is right, he says, that there is no homunculus in the brain, making our decisions for us. But the question remains, how do all those parallel computations become integrated, and how does the self feel that "I" made the decision? Science has yet to answer the binding problem of decision-making.
In response to the accusation that he is rehashing old ideas, Singer points out that the German newspaper debate got under way without him, and he was merely responding. So the more interesting question, perhaps, is why the public is interested again now. One reason, he thinks, is that people look at their societies, see that the totalitarian ones failed, and realise that the most complex are self-organising and impossible to steer or control. "You free yourself from authorities, including the gods, but you find yourself part of an evolving system," he says. "Now you realise that you don't really have influence on the dynamics of the systems in which you are. I think this gives a feeling of helplessness."
· Keiner kann anders, als er ist, by Wolf Singer, Frankfurter Allgemeine Zeitung, January 8 2004 (in German only; his original essay)
· How Free Are You? The Determinism Problem, by Ted Honderich (Oxford University Press, 2002) ISBN 0199251975
· The Volitional Brain: Towards a Neuroscience of Free Will, by Benjamin Libet (ed) et al (Imprint Academic, 2000) ISBN 0907845509