Last week we explored why rich kids get better SATs, which hinged on whether adopted children fare better if they grow up in a wealthy home. The nature verse nurture debate is as irresistible as it is unresolvable, and some of the brightest minds on the web are now weighing in. Their answers all come in the tricky language of EconoWonk, a strange tounge native to PhD holders, so The Wire hooked up its custom translator to help the rest of us understand. Does growing up rich make you smarter, or is it all about genes?

  • Half Nature, Half Nurture  Brad DeLong crunched some serious numbers, evaluating everything from the heritability of a high IQ to how well the SAT tests IQ to the effect of family income on IQ. He concludes that, roughly, "half of the income-test score correlation is due to the correlation of your test scores with your parents' IQ; and half of the income-test score correlation is coing purely from the advantages provided by that component of wealth uncorrelated with your parents' (genetic and environmental!) IQ."

    In English: Half of the credit for good SATs goes to inherited intelligence, half to the benefits of growing up with more money.
  • Adoption Proves Genes Matter Most  Alex Tabarrok took a longer view. Studying data on adopted children who are now adults, he found that children grow up to be more successful if their biological parents were more successful. However, people are not influenced by the success of their adoptive parents. A graph of the results is here. Tabarrok argued that adoptive parents are not good predictors for how their children will do in life, but biological parents are. "The effect for father's years of education is even larger; about a ten times larger effect on biological children than on adoptees," he wrote. "Parent income has a negligible effect, small and not statistically significant, on an adoptee completing college but an 8 times larger and statistically significant effect on a biological child completing college

    In English: If growing up wealthy helped promote success, adopted children would be more successful when their adoptive parents are richer. But this is not the case. However, people tend to be more successful when their biological parents are more successful. Therefore, intelligence is almost purely inherited.
  • Economists Fail at Explaining Biology  Mike Konczal debunked the hell out of Tabarrok's argument, poking a series of holes in his data and logic. It turns out that Tabarrok was comparing people of different ages--of course people in their 20s make less money than people in their 30s--and of different gender. Konczal concluded that Tabarrok's logic "gives off a bad impression of what economists can do with subtly," which in EconoWonk is a serious slam. "There’s nothing in the education of economists, which is training in a subset of engineering math techniques known as 'convex optimization', that prepares one for the biological sciences." Felix Salmon piled on as well.

    In English: Tabarrok is wrong, intelligence is not purely inherited. Maybe economists should stick to economics and not mess with hard sciences like biology.
  • Level the Playing Field  Karl Smith surveyed the debate and said his peers were acting irrationally. "I sense, perhaps incorrectly, a certain fear among left leaning bloggers that heritability of income will undermine their efforts at a progressive tax system," he wrote. "That seems exactly backwards to me. If we ever get to the point where income differences are almost all genetic then that’s a very strong argument for redistribution. Redistribution would have little economic effect since your genes are fixed and it would be compensating people for something that is completely beyond their control."

    In English: If people like Tabarrok are right that it's nature and not nurture, then people cursed with bad genes should be taxed less, while people unfairly advantaged with better genes should be taxed more.