Nature vs nurture

Do people differ psychologically from each other more because of their biology or because of their environment? I used to not think about this much, and when I did I would definitely favor the environment. I've always had a utopian side which wants to believe in the underlying good and limitless malleability of people. But I've also had a curiosity for the truth, and science (and real life) have a way of shaking even the most cherished beliefs of anyone with an open mind.

Part of it is that I can't resist a good, high stakes debate. Think about the huge implications-- if the environment is responsible for most of our differences, then there are concrete changes that we can make to start making things a lot more fair and equal in our educational system and the economy. If genes are responsible for most of our differences, then we're living under the veil of a huge cultural myth and our understanding of ourselves as a species is greatly hampered. Either way, brash teenager that I was, I set out a few years ago to solve the puzzle of nature vs nurture.

A huge amount of research has been done on the genes vs environment question, and it can be overwhelming at first. But, as with all things, you eventually start getting a hold of it. The surprising finding from the research is that genes are more important than we'd expect, and that the environment doesn't work in the way we'd expect it to.

The best controlled studies-- those of twins or adopted kids-- find that which (first world) family you're raised in has little or no effect on your later personality or intellect as an adult. To give a concrete example, there tends to be little or no correlation between an adult adoptee and his parents for IQ, personality traits, or psychopathology. This flies in the face of research by developmental psychologists who have been reporting correlations between kids and their parents for years, but never controlling for heredity.

The twin and adoption studies have various problems, though, which might be biasing them significantly against the family environment. I've dabbled quite a bit in that debate, and even wrote an article arguing for the importance of which family you're raised in for your eventual IQ. Debates over social science statistics are incredibly difficult, so my policy is to remain skeptical but open to differing viewpoints and theories.

While the significance and nature of environmental influences remains unclear, no one thinks that genes don't play a significant role in psychological differences. So, this decade will be a very interesting one, as big studies using new genome-scanning technology discover the genes underlying everything from Crohn's disease to neuroticism.