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Tuesday, June 02, 2009

Nature vs. nurture: Intriguing new research

In "Nature v nurture? Please don't ask", Mark Henderson believes we have an answer to the question of whether you are born bad or grow that way through experiences (The Times March 28, 2009):
Even more striking evidence has come from a recent series of studies led by Avshalom Caspi and Terrie Moffitt. These scientists have been following up a cohort of children born in 1972-73 in Dunedin, New Zealand, recording details of their life experiences and testing their DNA. The results have demolished the nature- nurture dichotomy.

First, Moffitt and Caspi studied a gene called MAOA, which has two variants or alleles. Boys with one allele are more likely to behave antisocially and get into trouble with the law - but only if they were also maltreated as children. When raised in well-adjusted families, those with the “risky” allele are fine. It is not a gene “for” criminality, and no determinism - genetic or environmental - is involved. A genetic variant must be activated by an environmental influence to do any potential harm.

The serotonin transporter gene, 5HTT, also has two alleles, and is known to be involved in mood. Moffitt and Caspi found that people with one allele were 2.5 times more likely to develop clinical depression than those with the other - but, again, only under particular circumstances. The risk applies only to people who also experience stressful life events such as unemployment, divorce or bereavement. When their environments are happy, their genotypes made no difference.
Well, that at least begins to make some sense, whether or not it is correct.

The way a child is raised is critical because it tells the child what he should think is a reasonable way to behave. Children are not a blank slate, but whatever we write on the slate, early on, matters.

Consider the difference between "Most people in this community are decent people who work hard and want the same things we want" vs. "You can't trust anyone who isn't a close blood relative".

Which will produce a more socially useful individual in a technologically advanced democracy?


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