New paper on gene-environment interaction

The authors include Eric Turkheimer and the abstract is here (link to paper requires a university connection I believe):

Recent research in behavioral genetics has found evidence for a Gene × Environment interaction on cognitive ability: Individual differences in cognitive ability among children raised in socioeconomically advantaged homes are primarily due to genes, whereas environmental factors are more influential for children from disadvantaged homes. We investigated the developmental origins of this interaction in a sample of 750 pairs of twins measured on the Bayley Short Form test of infant mental ability, once at age 10 months and again at age 2 years. A Gene × Environment interaction was evident on the longitudinal change in mental ability over the study period. At age 10 months, genes accounted for negligible variation in mental ability across all levels of socioeconomic status (SES). However, genetic influences emerged over the course of development, with larger genetic influences emerging for infants raised in higher-SES homes. At age 2 years, genes accounted for nearly 50% of the variation in mental ability of children raised in high-SES homes, but genes continued to account for negligible variation in mental ability of children raised in low-SES homes.

I found this to be an important paper.  One lesson is further confirmation that environment matters more for people in less fortunate circumstances (oddly, Progressive "dream policies" would bring about a world where genes matter much more at the margin than they do today).  A second lesson is how early "early intervention" has to be for potency, two years and under and that is assuming the procedures work in the first place.  The authors criticize Heckman but they do not follow up with much explanation.

For the pointer to the paper I thank Michelle Dawson.  Via Bryan Caplan, here are other papers by Turkheimer.


"(oddly, Progressive "dream policies" would bring about a world where genes matter much more at the margin than they do today)"


If there are two main contributing factors to a problem and you remove one, then it is reasonable to assume that two things will happen: the problem will be smaller, and the other factor will dominate the remaining problem.

Interesting that our kind host ignores the former and turns the latter into a potshot at progressives with those three little words, "at the margin." One can't help but admire the economy of language.

Maybe I am making a wrong assumption that study is comparing those poor in poor countries to middle and upper class westerners but if not:

I always think define "less fortunate circumstances".

Surely if you lock a child in closet he will not achieve his potential on the other hand I have trouble see much difference between poor USA household environments and those of the middle class. I was just in Honduras and seems upper class Honduran households often have less stuff than many poor USA households.

The TV and radio ubiquitous in the USA exposes a people to wide range of things (even Sesame street if people choose). Further kids can be as creative with rocks as with Legos. Wic, Food stamps and the fact that food is fortified would seem to provide ample nutrition as is seen in the fact that USA poor are generally overweight.

I am perplexed what would be the mechanism?

BTW I think that PBS and NPR might be best educational things the Government does, I am a supporter of both.

How long before the Forces of Progress suggest seizing the children of poor families as soon as they are weaned and raising them in Environmental Enrichment Facilities? There are historical precedents, I'd think.

"Marginal Revolution comes out in favor of early childhood enrichment for low SES children."

Not to put words your mouth Bill, but that doesn't necessarily follow. It's likely that the worthwhile environmental enrichment is pre-conception and the first month or trimester of pregnancy.

"One lesson is further confirmation that environment matters more for people in less fortunate circumstances"

No, you didn't read the quote. Environment matters more for 10-MONTH-OLDS and TWO-YEAR OLDS taking "IQ TESTS".

This paper says NOTHING about the more important issue of what matters for general life outcomes of adults.

Jeff beat me to the punch on this one, but this seems like a weird cheap shot:

(oddly, Progressive "dream policies" would bring about a world where genes matter much more at the margin than they do today)

Well, yes, of course. Similarly, eliminating cretinism due to iodine deficiency will lead to a world in which genes matter more at the margin than they do today. What point were you trying to make here?

It still doesn't follow even if the effective 'intervention' is probably achieved by a tablespoon full of micronutrients along with some anti-oxidants and Omega-3 from algae and possibly an air purifier. And that's my view, that everything is structural and everything else is remediable.

Funny, I thought dearieme was talking about the USSR. Or... here... to my Great-grandmother...whose father was a reservation statistic, and whose mother died in childbirth.

There is no limit to the evils perpetrated by those who are certain that they know how to improve the lot of others by making decisions for them.

Forced conversions, family separations, forced confessions, forced migrations, and so on. (And yes, I include the "Great" Society programs among those that destroyed the already-weak black lower-class family in the US.)


As for the specifics of this study, there is way too much lacking in what we are told to draw useful conclusions. First, by "poor", do you mean poor (as in Africa) or "poor" as in the US? Second, by "environmental factors", do you mean sanitation & available calories or stimulation & "balanced" input? On & on. Really, I don't think that there is a whole lot to what's been stated.

This only further confirms the meaninglessness of the nature/nurture divide. The question never should have been "what's more important, nature or nurture?". It should be "What is the minimum environment necessary to maximize heredity?".

Logically, this finding would seem to imply that upper-middle class working mothers who hire poor women to take care of their babies from 10 months to 24 months of age are damaging their children.

Steve, hiring a poor woman to nanny your children does not suddenly put them in the equivalent of a disadvantaged home.

It doesn't follow *logically* -- as you say -- that such is the case. This study sheds no light on that situation. A different study would be required to test your hypothesis. I'd wager my farm that such a study would show that "hiring a poor woman to nanny your children does not suddenly put them in the equivalent of a disadvantaged home with regards to IQ results."

Tyler claims this is an important finding. Okay, what, then, are the implications?

Well, one fashionable explanation for IQ gaps has been, in recent years, the "millions of words" theory: upper middle class mothers direct huge numbers of intelligent words at their children, while underclass women direct smaller amounts of less explanatory verbiage at their children. This correlation is then used to argue for various social programs that take underclass children away from their mothers and grandmothers for large numbers of hours per day and put in the care of well-paid college graduates.

Yet, the converse idea that upper middle class women leaving their children in the care of minimum wage women for ten hours or so per day might have implications for the development of their children's intelligence is, to say the least, not popular with the upper middle class career women who dominate discourse on this subject in the press and academia.


I expend no energy distancing myself from anyone, not even you. Don't hate me because I'm tolerant.

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