In 1872, physician George Huntington identified a disease. Huntington's disease, which begins in a person's thirties, manifests as occasional jerking movements and continues on to behavioural changes: apathy, irritability or moodiness progressing to memory loss, dementia or schizophrenia. The cause of all of this has been traced to a modification of a single gene that we all carry on our chromosome 4.
This is a clear example of a significant alteration of behaviour traced to a single gene. However, no one has convincingly traced a non-pathological cognitive or behavioural trait to a single gene.
Genetically identical animals placed in different environments respond differently. Is it our natures or our environment that makes us who we are?
The question is not of mere academic interest, obviously; it bears on how we educate our children, understand sexuality, even the very core of our personalities. It has spawned political movements ranging from Nazism (nature) to Marxism (nurture). Everyone from anthropologists to zoologists has weighed in on the debate. Shakespeare, as usual, has a bon mot (and probably inspired the "nature v nurture" phrase) with Prospero's declamation that Caliban is "a devil, a born devil, on whose nature nurture can never stick".
The philosophical roots of the debate date back to antiquity. Plato, on the nature side, argued that because ideals represent perfection, they could not possibly be derived from individuals' imperfect experience, and so were innate.
On the other side of the debate, Locke argued that every thought or action has its origins in experience. Kant's modern resolution was to argue that the form of thought and action is intrinsic, but experience provides the content. For all the lip service paid to the idea that both nature and nurture contribute, we very quickly settle down to polarised positions even in current debate.
The via media of the compromise, that it is both nature and nurture, is confounded by the fact that they interact with one another. For example, current treatment for galactosemia involves removing all natural forms of milk from the infant's diet. (Galactosemia is an inherited disorder in which galactose, a sugar found in milk, is not metabolised by the body because of an enzyme deficiency.) The infant will develop normally, but because this child will never have had to digest milk, he or she will never develop the ability to digest lactose, another sugar found in milk. So, in this case, lactose intolerance arises due to nurture, which in turn was caused by nature.
When it comes to cognition or personality or behaviour, nature and nurture seem to interact in ways that are far more complex and nonlinear. Two and two don't always add up to four.
These complex interactions are just beginning to be mapped out by the latest research. The central organ involved is the brain. Current neuroscientific findings per se are far from providing definitive answers, but they could help us find novel ways of thinking about this issue. John Dowling, a professor of neuroscience (formerly the director of the programme in mind, brain and behaviour at Harvard University), serves as an able guide with The Great Brain Debate . It is part of the National Academies' series Science Essentials and is an admittedly simple, but highly accurate, slim, readable account of the latest studies of the brain as it develops, matures and ages.
Dowling is at his best when he discusses vision, but just as expertly serves up issues in language acquisition, birdsong or memory formation. He does all this in a simple, direct and very friendly genial tone that makes the book a highly accessible read. Even if "nature v nurture" questions do not keep you awake at night, the book is an enjoyable primer on some of the most exciting areas of neuroscience research today.
My very minor gripe is that the book would perhaps be substantially more accessible with better images or somewhat more professional illustrations.
Dowling does not confine himself to merely describing relevant neuroscientific findings. He also presents a fair-minded account of the current controversies and his own speculations. His is a very interesting, readable book that will leave you better informed to participate in the continuing debate.
A. K. Prashanth is a research scientist at the University of California, Davis, US.
The Great Brain Debate: Nature or Nurture?
Author - John E. Dowling
Publisher - Joseph Henry Press
Pages - 189
Price - £16.95
ISBN - 0 309 09223 X