The Infant IQ Gap

Micha's post below quotes a description of Roland Fryer's purported debunking of the black-white IQ gap:

Are blacks genetically predisposed to be less intelligent than whites? With a collaborator from the University of Chicago, Mr Fryer debunked this idea. Granted, blacks score worse than whites on intelligence tests. But Mr Fryer looked at data from new tests on very young children. At eight months to a year, he found almost no racial gap, and that gap disappeared entirely when he added controls for such things as low birth weight.

The paper, co-authored with Steven Levitt, is here (PDF).

While I think it would be great if environmental adjustments could correct the IQ gap, and I hope Dr. Fryer is successful in finding a solution, this is by no means a debunking of the genetic hypothesis.

For one, it's not at all clear that infant testing measures the same underlying factor as adult IQ tests. The test used is the Bayley Scale of Infant Development, which according to the paper has a correlation of 0.3 with IQ at age 5, meaning that it explains only 9% of the variation in IQ at the age of 5, and the correlation with adult IQ is presumably somewhat weaker. It's likely that BSID is more a measure of normal development than of genetic potential for intelligence. Note the reference to low birth weight babies having lower BSID scores, and also this study, which found that BSID weakly predicted IQ in children exposed to an environmental toxin but not at all in the matched controls.

Or it could be the case that black and white children simply develop along different trajectories. This is consistent with adoption studies, which have found that the IQ gap between black and white children adopted into white families starts small and grows over time. Granted, this is not the only possible explanation (e.g., it could be due to peer group effects).

Also worth noting: At eight months to a year, there is no sexual gap in facial hair growth.

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Heritability increases with age

You become more like your identical twin as an adult than you were as a child. Karl Smith hypothesizes that when we are young our lives are partially controlled by others. As we get older our own preferences dominate.

As kids, we have a greater

As kids, we have a greater learning capacity than we have when we get older. Actually, this capacity fades away in time. I believe that my IQ was greater at the age of 5 than it is now. When I say this I don't mean numbers but fractions involving both IQ and the age factor.
Johanna Bartley, Key Account Manager for Thermal Paper Industries.