The New York Times Economix blog found "a very strong positive correlation between income and test scores," which they illustrate in the above graph comparing SAT scores to family income. In a nutshell, it shows that kids from wealthier families do better at the SATs.
- Smart Parents Get Rich, Have Smart Kids Greg Mankiw, looking at this data, concluded that the correlation isn't due primaily to, say, wealthier parents being able to afford private school tuition or pricey tutors. Rather, Mankiw credited "parents' IQ," suggesting that wealthy parents are rich because they're smart, and that their kids inherit that intelligence. "Smart parents make more money and pass those good genes on to their offspring," he wrote.
- What Do Adopted Kids Prove? Mankiw argued that removing the genetic variable would prove his point. "It would be interesting to see the above graph reproduced for adopted children only. I bet that the curve would be a lot flatter." That is, he speculates that adopted children will not fare any better under richer parents, thus proving Mankiw's theory that the key cause of SAT success is good genes.
But the Atlantic's own Conor Clarke disagreed, citing a book titled "Intelligence and How to Get It: Why Schools and Cultures Count." Specifically, he pointed to a chapter on "Heritability and Mutability." Clarke wrote, "It took 15 seconds of googling to find problems with the mankiw theory: high-income adoptees are 12 IQ points higher." In other words, kids adopted by rich parents do better on IQ tests than kids adopted by less wealthy parents. From the book:
As it turns out, both genes and class-related environmental effects are powerful contributors to intelligence.
[...] The crucial finding is that children adopted by high-SES parents had IQs that averaged 12 points higher than the IQs of those adopted by low-SES parents--and this was true whether the biological mothers of the children were of low or high SES. So the study showed that being raised in a higher-social-class environment produces children with far higher IQ than does being raised in lower-social-class environments. Equally important, the school achievement of children raised in upper-middle-class environments was much higher than that of children raised in lower-class environments.