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
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
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
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.