Nature versus nurture: the battle that can’t be won

It was entertaining to hear Professor Anita Thapar and Oliver James almost coming to blows on BBC Radio 4’s Today programme this morning, but as ever it was an exchange that was more useful as a demonstration of a possible, ecologically sound, new heating system than it was an alternative to low energy bulbs. The cause of their heated but not especially enlightening contretemps was the former’s recently published work on an alleged link between Attention Deficit Hyperactivity Disorder (thankfully usually referred to as the less mouth-filling ADHD) and genetic variation.

Their dispute raises a myriad of important issues about health, responsibility, the public understanding of science, and research funding to name merely the most obvious. When we get to the human frailties of scientists – hubris, defence of reputation, wishful thinking, political allegiances and the like – the merely hard to discern tips over into the impenetrably murky.

At root this is the familiar “nature versus nurture” debate. It seems to me to be an ultimately sterile one. There is no choice between these two causations except in the most trivial of human attributes. Yes, I have brown eyes (rather beautiful ones as it happens, or so I’ve been told by women with an axe to grind) and my son has the most stunning, virtually pitch black ones. I doubt very much that had he or I been nurtured differently I would have had his objectively wonderful eyes, and he’d have had to put up with the more subjective charms of mine. But once we get past these simple physical attributes, there is no line between nature and nurture that we can trace reliably. Rather there is a complex inter-twining that is beyond the reach of almost any conceivably ethical experimentation. And without an adequate experimental framework the best we can do is to try and make inferences, and that is always fraught with the risks that boiled over in the irate exchange this morning.

The risks I’ve described are unavoidable because we cannot subject human beings to the experimental controls that might truly elucidate the interface between nature and nurture. But added to this inescapable theoretical level of risk are all the other pitfalls of human weakness. In the case of ADHD, parents are desperate to be told that their children have an objective biological condition that allows them to evade the notion that it is their parenting that is at fault. The drug companies that manufacture Ritalin have a clear vested interest in a medicalising model of the disorder. Scientists such as Professor Thapar do not come to these problems with the neutrality that they claim. They are investigating particular theories and their research budgets and scientific reputations depend on, in this case, proving a genetic link rather than disproving such a link. And of course there is the hoary old issue of statistical significance. On further scrutiny of Professor Thapar’s paper it emerges that only 10% of the children they studied with diagnosed ADHD had the particular genetic variant that they were investigating. So is this weak proof of a link, or are the 90% that didn’t have this variant proof, as Oliver James very stridently claimed, that such a link is fantasy?

When we subject human beings to the reductive modelling of scientific investigation, we tread a perilous path indeed. The history of science is littered with outrageous fallacies from phrenology to the discredited links between intelligence and race. Humans and their societies are so complex, the webs of cause and effect so diffuse, and the feedback mechanisms so impenetrable and long-delayed that it is near impossible to arrive at any kind of resolution to the nature versus nurture debate that isn’t bounded by qualification after qualification.

What can we say with certainty? That anyone who claims that this one piece of evidence proves that nature has been definitively crowned the winner in the battle is either simply wrong, or possibly wrong and lying to boot. This is not to suggest that we should not be investigating this infinitely fascinating and intriguing relationship: merely that scepticism is always, and without exception, the safest response to the inevitably provisional results.

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