Blog Post

AEIdeas

Yesterday, the Washington Post described an academic study that has been getting a lot of press recently. The authors used brain scans of 1,100 children and young adults to demonstrate that the surface area of the cerebral cortex of poor children was 6% smaller than those of affluent families, and that they also scored lower on a battery of cognitive tests. Their conclusion was that poverty was the causal factor. The Post article quotes the author of a similar study that will be published soon, who emphatically agreed. “The thing that really stands out is how powerful the economic influences are on something as fundamental as brain structure. It’s just very striking.”

I’m baffled by this confidence that poverty is the cause. If you’re not, let’s find out why. Please take out your #2 pencils and begin.

1.) IQ scores and brain size are correlated.

a.) False. Stephen Jay Gould refuted that years ago, showing that 19th century anthropologists fudged their data to make it look that way.

b.) True. The correlation has been found consistently across many ways of measuring brain size, most recently by MRI studies measuring both whole brain size and the size of specific regions of the brain. We now know that Gould himself misrepresented the work of the specific 19th-century scientist whom he libeled.

2.) IQ scores and income are correlated.

a.) False. Don’t pay attention to the pseudoscientists who say otherwise.

b.) True, over many kinds of IQ tests and in many different countries, including studies in which the IQ tests were administered as children and correlated with their adult income, and after controlling for parental socioeconomic status.

3.) IQ is substantially heritable.

a.) False. Don’t pay attention to the pseudoscientists who say otherwise.

b.) True. The only uncertainty is exactly how much, with 50% being a common estimate, along with a consensus that the environmental component is dominated by the “nonshared” environment—i.e., not such things as family income, number of books in the home, number of words heard by age five, and the rest of the usual suspects.

4.) In a study of 1,100 children, it was discovered that the surface area of the cerebral cortex of poor children was 6% smaller than those of affluent families, and that they also scored lower on a battery of cognitive tests. The parsimonious explanation for these findings is:

a.) Growing up in affluence grows the brain.

b.) Parental IQ.

If you answered questions #1, #2, and #3 as “true,” congratulations! You are willing to acknowledge thoroughly documented aspects of the world we live in.

If you answered question #4 with “a,” congratulations! You have the right stuff to have your study published in a prestigious academic journal, to gain widespread media coverage, and to have your findings used as justification for landmark changes in early childcare.

But if you answered question #4 with “a,” one last question: What do you think of Occam’s Razor?

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