Nature to nurture

PUBLISHED : Thursday, 29 October, 2009, 12:00am
UPDATED : Thursday, 29 October, 2009, 12:00am

One of the oldest debates in social science is that on nature versus nurture when it comes to human development. It seems everyone has vague beliefs and convictions, however implicit, on the question. If the two stances represent the two poles on a continuum, most people probably have a position somewhere in between, with some closer to one pole than the other; rare would be the person who takes one extreme or the other. Such debates can become sterile, however, as when social scientists adopt a dogmatic stance regarding one or the other position. They can be horrifying, as when tyrannical idealists such as Robespierre, Mao Zedong and Pol Pot saw those they ruled as a clean slate to be moulded to fit their own ideological liking. Thankfully, we no longer see human nature in such dangerously simplistic terms.

In the 1960s, two young scientists, Torsten Wiesel and David Hubel, were to transform the terms - and our understanding - of these debates forever. Wiesel, a long-time science adviser to the central government and champion of various human rights and humanitarian causes such as eye disease research in Chengdu , was passing through Hong Kong this month and was interviewed by the South China Morning Post.

The scientific duo won the Nobel Prize in physiology or medicine in 1981. At first glance, their highly technical research on the development of the visual nerve cells of newborn kittens looks uninteresting to anyone but specialists. As a specialised field, their work provided researchers with a much better understanding of mammalian vision and sensory processing. It also helped spur clinical research on eye diseases.

But it was through the work of the American Noam Chomsky and the revolution in linguistics he wrought in the 1960s that the pair came to exercise a profound influence on cognitive science and our view of human nature.

In their research, Wiesel and Hubel showed that kittens deprived of light stimuli failed to develop nerve cells necessary for the growth of their primary visual cortex; they became visually impaired. They also found there is a predetermined critical period of post-natal development when neural connections for vision need to develop properly from environmental influences. Once this critical period is past, exposure to light would no longer stimulate neural development. Equally interesting is their finding that our perception of line, angle and depth is predetermined by the development of our visual cortex; so, by reflex, we see objects and movements in the world in certain genetically predetermined ways. In terms of visual development, nature and nurture clearly have equally important roles.

When Chomsky first read Wiesel and Hubel, he immediately realised their significance for linguistics. Parents have long recognised that there is a critical period for young children to learn their native language, after which their language acquisition abilities decline and disappear. Similar to the visual cortex, Chomsky came to believe there are grammatical and other cognitive structures that are innate or genetically predetermined; they are, therefore universal. But they require appropriate external stimuli such as exposure to a linguistic environment for such structures to develop in the young mind. This is borne out in extreme child abuse or isolation cases where children missed their critical language-learning period and became cognitively impaired. Umberto Eco, in Dreams for the Perfect Language, tells the story of how Frederick II wanted to know what the first human language was. So he forbade wet nurses to speak to a group of infants to see what their first word would be; the babies all died.

Probably all our cognitive abilities and sensory processing require a combination of nature and nurture to flourish. Chomsky and Wiesel show this conclusion is not a wishy-washy cop out, but the way things really are. Their vision of human nature is a profoundly humane one. They make us realise that, when people are prevented from reaching their cognitive and moral potential, it amounts to an assault on their humanity.

Alex Lo is a senior writer at the Post