If You’re So Smart, Maybe It’s Because You’re Rich

Richard Nisbett and colleagues have produced an erudite and accessible review of recent research on human intelligence (pdf here). The 300 references in the review put paid to the claims of Anneli Rufus and Andrew Sullivan that political correctness has killed off the study of intelligence. Researchers have been studying intelligence with vigor, including hot topics such as social class and racial differences in IQ.

The whole review is worth a careful read, but a particularly intriguing finding is that adopted children have significantly higher IQs than their non-adopted biological siblings. Most adoptions involve a child moving from a lower to a higher socioeconomic family environment. The effect of the environmental change is dramatic: 12 IQ points on average.

Family environment research offers plausible explanations for why adopted children have so much higher IQs than their genetically-similar siblings. Relative to children raised in poor or working class homes, children raised in middle and upper-income families hear several times as many words by the age of three, receive substantially more parental encouragement, have greater access to books and magazines, and are more likely to have parents who read to them.

It has long been known that the average IQ of poor children is lower than that of their wealthier counterparts. The optimistic implication of the “adoption effect” is that these differences are driven by environment rather than genetics. Public policies that facilitate the emergence of IQ-enhancing family environments throughout the population could therefore benefit a range of lower-income kids, rather than letting fate restrict the class-driven IQ bump to those kids who happen to get adopted by better off families.


  1. dave schutz says

    “..Public policies that facilitate the emergence of IQ-enhancing family environments..” You have in mind what, exactly? Putting up a rabbit-proof fence and bringing all the poor kids onto the rich side? Many Ladies Bountiful descending on neighborhoods and putting restricters on the TVs so they only show Dora and Sesame Street?

    • Allen K. says

      I had the same thought, wondering if there had been comparison studies between adopted aborigines and non-adopted.

      • Bostonian in Brooklyn says

        Why were some siblings adopted and others not adopted? Were the adopted ones cuter?

        But another mystery for which I have only anecdotal evidence; why are my and my friends grandchildren doing things earlier (so maybe smarter?) than our children. Our children were not raised in impoverished environments. They were well-fed, well-attended, much photographed, lovingly mothered, fathered and grandparented. Sesame streeted, Electric Companied and Dr. Seussed.

        Is it computers? Is it better pre-natal vitamins?

        We also want to know why our daughters have our height but bigger feet. My childhood memories do not include foot-binding. But that question, while more focused, is less important.

      • matt w says

        Maybe also more bookmobiles? Or just an end to the top-down class warfare we’ve been experiencing, because I bet kids would have more IQ-enhancing family environments if their parents had more money?

        • Katja says

          You don’t have to sell me on the benefits of fighting poverty. Poverty and especially child poverty as one of the root causes of America’s ills is normally my shtick.

          But I was simply putting forward a simple and practical policy proposal.

  2. Wido Incognitus says

    1. The far-right still is going to love the Minnesota Twins study and use its evidence of a genetic component for intelligence to explain differences in intelligence as being genetic and environmental uniformly across all people. Of course, the far-right is also full of Santorum-style disdain for “smart people” who try to ask questions on some level. Intelligence, like any other form of personal characteristic or accomplishment, is for them at best a justification for hierarchy among all people and at worst an excuse for cruelty by their tribe.
    2. Anyway, I am not sure what recommendations for new laws can be justified by this study (which I am, of course, too lazy to read), but always be careful about getting the government too involved in how parents raise their children. I am pretty sure that psychologists say that adoption itself can have negative effects on the child (too lazy for links) and foster-homes can be troubling places indeed (still too lazy for links).

    • Keith Humphreys says

      Warren: As I said in the post, the goal of public policy would not be related to adopted kids, but to all lower income kids. We have a history here of such policies as anyone who went to one of Carnegie’s libraries could attest.

    • Katja says

      Regarding your first point, the bigger problem with those people is that they don’t understand what heritability means in the first place (it’s not “children taking after their parents”). In particular, a shift of 12 IQ points (slightly less than one sigma) from an important environmental factor would easily be compatible even with a very high degree of heritability.

  3. says

    From the Nisbett paper: “The chief measure that we focus on in this article is IQ, because it is for that measure that the bulk of evidence pertinent to intelligence exists.” So IQ – the ability to solve trivial puzzles rapidly – is important because we study it.

    • says

      I think that’s not quite accurate — it’s important because we *can* study it. Lamp post, meet drunk. But, like democracy, it’s also pretty much what we have, because the socioeconomic success rates are confounded almost by definition.

      As a parent, meanwhile, I would suggest that even small differences in external conditions can make large differences in how much useful attention kids get.

      • sd says

        “As a parent, meanwhile, I would suggest that even small differences in external conditions can make large differences in how much useful attention kids get”

        I don’t understand this statement, but it sounds interesting. Can you please elaborate?

        • says

          It’s just the Micawber Principle, or , if you’re less literary, the effect of taking the difference between large numbers.

          Essentially: parents — most especially single parents — of smallish children typically have a load of essential stuff to do (sleeping, dressing, meals, ferrying, work, laundry, administrivia …) that properly adds up to somewhere between 22 and 26 hours a day. Of that, there’s an irreducible minimum of, say, 20 minutes spent with offspring that can’t be interleaved with anything else, mainly bedtime (and later homework help). So if you reduce other demands by a mere half hour, a parent can get double the amount of undivided time spent with kid(s) while still getting an extra 10 minutes of sleep or other rest, which will make the interleaved time that much more pleasant and and useful to the kid(s).

          (Anecdata: when we don’t sleep, the morning consists of getting kids dressed and breakfasted while having coffee, then shoving them out to school bus and daycare as quickly as possible, period; when we do, there’s time to ask whether they slept well, talk about what’s going to be happening in school, what they might want to do when they get home, even stories in the local newspaper. Much more pleasant and developmentally helpful. And we’re among the lucky.)

    • Igloo says

      James, there is strong, strong evidence that the ability to solve trivial puzzles quickly is strongly correlated with academic and job performance, as well as good judgment.

  4. Eli says

    The search on this stuff goes back decades. A huge landmark being that on language from Hart and Risley. Less mentioned is their findings on cognitive scaffolding and tone. All this stuff is huge, and educated, middle-class parents enjoy a privilege that can far outstrip mere finances.

    What can we do: Radically smaller class sizes in order to better address Maslow’s hierarchy issues. Separation of funding from property taxes to a more redistributionist system. The poorest neighborhoods have the greatest need for funding, with the lowest tax base. Statewide student and family tracking systems that follow at-risk families and target them for services. Home-nurse visits and parenting classes. Reduction of violence and incarceration in poor neighborhoods. Radical expansion of community colleges and technical training – each should have well-funded daycares on site (staffed by early childhood development students).