Failing the IQ test

Sociobiology has long been a sore spot for the Left, and with good reason. Our fundamental traits have a firm biological basis, shaped as they are by complex gene-environment interactions. And the more we discover how firmly ingrained our abilities, attitudes, and behaviors tend to be, the less plausible leftist social-intervention programs become.

No biological trait threatens that agenda more than intelligence. With standard IQ tests, we can measure and rank people on a continuum, allowing us to make reasonable predictions about their success in life. Granted, a good IQ score is not the whole story of a person's life--not even close--but it is the entrance requirement for most high-paying jobs, as well as a predictor of marital stability, law-abidingness, civic behavior, and many other positive life outcomes. Biology severely limits the aspirations of social engineers.

The Left's initial response to this argument was denial. Stephen Jay Gould's Mismeasure of Man, published in 1981, dismissed IQ research as pseudoscience used to pursue elitist and racist agendas. Much has changed since then, as psychologist Richard Nisbett's new book, Intelligence and How to Get It, demonstrates. Though emerging as a new favorite of the Left--the New York Times has sung its praises in three different articles--the book actually concedes much to the "hereditarian" crowd. Nisbett tells us that general intelligence exists, that it can be reliably measured by IQ tests, and that scores on such tests help to predict success in school and at work. He even acknowledges that intelligence is partially determined by genes.

He claims, for example, that East Asians are not smarter than Europeans, citing a 1991 review of the data, but his evidence is 18 years out of date.

But Intelligence and How to Get It departs from the orthodox view in an important way. Nisbett argues that IQ is far more malleable than hereditarians presume. He believes that individual IQ differences could be made much smaller, and he is confident that racial differences in average IQ, which have been stubbornly persistent, have no genetic basis. Since the environmental component to IQ is potentially quite large, Nisbett says, "we need intensive early childhood education for the poor, and we need home visitation to teach parents how to encourage intellectual development." Despite a yearly price tag of over $100 billion, Nisbett says these programs would more than pay for themselves.

The book has several strengths. It marshals an impressive amount of empirical evidence in a relatively short space. It wrestles comprehensively with the claims of the hereditarians. It acknowledges the failures of many past interventions and it urges more research before we dive into expensive government programs. But its thesis fails. The weight of the evidence shows that intelligence is a relatively rigid trait, still immune to large and permanent changes.

Nisbett opens by summarizing a standard view in behavioral genetics--that genes exert an increasingly large effect on children's intellectual makeup as they age. From adoption studies, we know that unrelated siblings adopted into the same home will have personality traits that resemble each other's while they are young. But by the time they are adults, the adopted siblings will have little more in common than two strangers. The adult adoptees resemble their biological family, but not their adoptive family.

Nisbett criticizes these studies. He says that children are often adopted into environments similar to the ones they came from, and too many adoption studies examine children who are simply transferred from one middle-class family to another. This compresses the range of childhood environments that we observe, reducing the statistical effect of nurture.

He cites instead eight other adoption studies--three directly, five via reference to a review article--that compare poor children adopted into wealthier homes with similar poor children who were not adopted. He concludes that the IQ gain for adopted kids is "between 12 and 18 IQ points," a strong claim. A 15-point change in IQ is one standard deviation--the difference between well below average and well above.

Nisbett makes these adoption studies the crux of his argument because they allegedly demonstrate the great possibilities of environmental intervention. He goes into great detail about how differences in parenting styles could affect a child's intelligence. He acknowledges that the correlation between bad parenting and low child IQ could really be due to genetic transmission, but he says that cannot be true because we know from adoption studies that home environments matter so much.

The problem is that none of the eight adoption studies Nisbett references show adult IQ scores. The last IQ evaluations of the adoptees typically occurred in the early teenage years and even earlier in some cases. It is well-known that the effects of the home environment are significant through early adolescence, and they do not typically fade until the late teens and early 20s. The studies Nisbett cites as "proof" that home environments matter are not inconsistent with the hereditarian view.

Unfortunately, no adoption study provides adult IQ data specifically for poor kids moved to wealthier homes. Yet we do know that adults who were adopted have IQ's that are about 13 points lower than non-adopted adults, even though the two groups show little difference during childhood. Overall, the adoption studies cited by Nisbett tell us much less than he wants. A major foundation of the book rests on an empirical claim that is at best optimistic.

But even if we knew that adoption works wonders, it cannot be a large-scale solution to the problem of low IQ. Government interventions can only hope to mimic whatever advantages adoption might provide, and even Nisbett is cautious about their efficacy. He admits that Head Start and a more intensive intervention called Perry Preschool failed to produce lasting IQ gains. He cites the Milwaukee project, the Abecedarian project, and the Infant Health and Development Program as examples of interventions that have raised IQ, but just how successful were they?

The Milwaukee project consisted of only 20 children. Despite a $14 million investment, their putative IQ gains did not improve their academic achievement after elementary school. The administrators of the project never published their results in a peer-reviewed journal, and, to top it all off, one of them was later sent to prison for misappropriating federal research funds. In an interview after his book was published, Nisbett admitted, "Knowing what I now do, I would never have cited the study." So scratch Milwaukee off the list.

Abecedarian and IHDP were much more respectable experiments, which claimed IQ gains of about five points by adulthood. These results are disputed--the Abecedarian control group may have had a lower initial IQ than the treatment group, and only the higher birth weight babies in IHDP showed any gains--but the technical details are less interesting than the narrow scope of the debate. The success stories, which require the most optimistic read of the data, involve raising IQ by five points or less. When success means moving people from the 16th to the 25th percentile of IQ as Abecedarian did, a strong dose of realism about raising IQ is needed.

While unwarranted optimism characterizes Nisbett's discussion of raising IQ, obfuscation best describes his treatment of racial differences in IQ. He claims, for example, that East Asians are not smarter than Europeans, citing a 1991 review of the data, but his evidence is 18 years out of date. Richard Lynn and his colleagues have since demonstrated that Asian Americans outscore white Americans by about four points on IQ tests, and East Asian countries have the highest national IQ's in the world. These results are scarcely mentioned.

Nisbett does say that Jews have higher IQ's than Gentiles, and that whites have higher IQ's than blacks, but his purely environmental explanations of these differences often beg questions. For example, Nisbett explains the superior IQ of Jews by citing the educational focus of Jewish culture, and he ascribes elevated visual-spatial ability among East Asians to a culture that emphasizes it. But where did these cultures come from? Nisbett never seriously considers that cultures themselves could have genetic origins.

A key assertion that Nisbett makes to argue that genes have nothing to do with the black-white IQ difference is that blacks have cut the deficit by more than one third over the past 30 years, implying that we can expect smaller differences over time. But recent gap narrowing is shown by only a single IQ test. Four other major IQ tests show no narrowing of the black-white gap among people born after the 1970s.

By de-emphasizing the role of nature in determining intelligence, Nisbett tries to reduce IQ to little more than an achievement measure. Achievement can be raised by better textbooks, better teachers, better home environments. No need to worry too much about biology, Nisbett is telling his readers. There is no need to face up to deep-seated individual and group differences in abilities, and to what implications they might have for a democratic society.

New York Times columnist Nicholas Kristof has already bought in. In an article entitled "Rising Above IQ," Kristof pronounced Intelligence and How to Get It "superb" because it allows him to avoid talking about intelligence differences. He and most of the Left can go on with the comfortable assumption that everyone has the same cognitive potential. But biological differences cannot be wished away.

Jason Richwine is a National Research Initiative fellow at AEI.

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