Friday, July 17, 2009

Achievement Beyond IQ: A Genetic Story   posted by Herrick @ 7/17/2009 11:45:00 AM

It's nice to see a bad idea demolished. And that's what Greven, et al. do in "More than just IQ." Their subtitle tells most of the story:
School achievement is predicted by self-perceived abilities (SPAs)--but for genetic rather than environmental reasons.

So asking kids "Are you good at math and English?" is indeed a good way to find out who is good at math and English; and basic twin-study methods show that the answers to those questions are in fact genetically-driven, with heritability of 51% and family environment explaining 2%.

Another family environment channel shot down. The authors drive that fact home:

Despite the fact that not a single twin or adoption study has investigated the genetic and environmental etiologies of SPAs, researchers have cited environmental factors as a leading causal explanation for constructs related to SPAs, such as self-efficacy...and self-concept..... Moreover, one of the most established theories of SPAs assumes that the development of individual differences in SPAs is shaped primarily by parents' beliefs, expectations, attitudes, and behaviors...

Of course, the bulk of the academic literature will surely go right on assuming that self-construct is driven by shared environment: "Surely, you don't mean to imply that an entire field of research was a waste of time, do you?" And in the policy and non-profit worlds these results won't stop those "Book in Every Home" campaigns. Alas....

More results:

The genetic component of self-perceived abilities (SPA) is a good predictor of achivement, after you control for IQ.

Even after you control for IQ and self-perceived ability, there's still a big genetic residual--about as big as IQ's genetic channel: So there are big genetic drivers of school achievement that don't fit into the two simple boxes of IQ and SPA. Sounds like an opportunity for some productive data-mining....

The big genetic residual fits in with the fact that a person's income is vastly more heritable than can be explained by the IQ channel alone. There are more things in gene expression, Horatio, than are dreamt of in your WAIS-R.

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