Why Rich Parents Raise Smarter Children

Over at the Economix blog, Catherine Rampell produces the following graph, which shows the relationship between SAT test score and family income:

income and test scores.png

Greg Mankiw calls this the "Least Surprising Correlation of All Time" and writes:

Of course! But so what? This fact tells us nothing about the causal impact of income on test scores. [...] This graph is a good example of omitted variable bias, a statistical issue discussed in Chapter 2 of my favorite textbook. The key omitted variable here is parents' IQ. Smart parents make more money and pass those good genes on to their offspring. [...] It would be interesting to see the above graph reproduced for adopted children only. I bet that the curve would be a lot flatter.

And sure, it wouldn't be surprising to find a correlation between high IQ and high income. And it wouldn't be surprising to learn that "intelligence" is partially inheritable. But the vaguely deterministic suggestion that smart parents "make more money and pass those good genes on to their offspring" is a laughably crude description of how real life works.    

I don't know of any large studies that test the relationship between test scores and socioeconomic status in adopted children. But the closest adoption study described in Richard Nisbett's Intelligence and How to Get It: Why Schools and Cultures Count (I'll put the full citation at the bottom) has this to say about IQ and socioeconomic status (SES):

IQ and SES.pngThe obvious point to make here is that children born to wealthy parents and raised by downscale families have almost exactly the same IQ range as children born to downscale parents and raised by wealthy families. Nisbett uses this to make what I thought would have been an entirely uncontroversial point -- namely, that "both genes and class-related environmental effects are powerful contributors to intelligence"

And is it really hard to figure out why those "class-related environmental effects" should make a difference? Better schools, better nutrition, better health care, better test preparation and better neighborhoods all come to mind. I'm sure an intelligent guy like Greg Mankiw can figure that out.

(John Sides reports on some other studies and makes some good points here. The chart above is drawn from Capron & Duyme, "Assessment of Effects of Socioeconomic Status on IQ in a Full Cross-Fostering Study" (1989).)
Presented by

Conor Clarke is the editor, with Michael Kinsley, of Creative Capitalism. He was previously a fellow at The Atlantic and an editor at The Guardian. More

Conor Clarke is the editor, with Michael Kinsley, of Creative Capitalism, an economics blog that was recently published in book form by Simon and Schuster. He was previously a fellow at The Atlantic and an editor at The Guardian. He is also on Twitter.

Does This Child Need Marijuana?

Dravet Syndrome is a severe form of epilepsy that affects children. Could marijuana oils alleviate their seizures?

Join the Discussion

After you comment, click Post. If you’re not already logged in you will be asked to log in or register with Disqus.

Please note that The Atlantic's account system is separate from our commenting system. To log in or register with The Atlantic, use the Sign In button at the top of every page.

blog comments powered by Disqus


Does This Child Need Marijuana?

Inside a family's fight to use marijuana oils to treat epilepsy


A Miniature 1950s Utopia

A reclusive artist built this idealized suburb to grapple with his painful childhood memories.


Why Principals Matter

Nadia Lopez didn't think anybody cared about her school. Then the Internet heard her story.


A History of Contraception

In the 16th century, men used linen condoms laced shut with ribbons.


'A Music That Has No End'

In Spain, a flamenco guitarist hustles to make a modest living.

More in Politics

Just In