The Bell Curve: Intelligence and Class Structure in American Life (68 page)

At the end of the fifth year, the children receiving the day care outscored those who did not by half a standard deviation on an intelligence test. At last report, the children were 12 years old and were still doing better intellectually than the controls. Combining all the cohorts, only 28 percent of the experimental children had repeated a grade, compared to 55 percent of the control children. Only 13 percent of the experimental children had IQs of less than 85, compared to 44 percent of the control children.
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This would be unequivocal good news, except for charges that the two groups were not comparable in their intellectual prospects at birth. Ignoring the more technical issues, the major stumbling block to deciding what the Abecedarian Project has accomplished is that the experimental children had already outscored the controls on cognitive performance tests by at least as large a margin (in standard score units) by the age of 1 or 2 years, and perhaps even by 6 months, as they had after nearly five years of intensive day care.
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There are two main explanations for this anomaly. Perhaps the intervention had achieved all its effects in the first months or the first year of the project (which, if true, would have important policy implications). Or perhaps the experimental and control groups were different to begin with (the sample sizes for any of the experimental or control groups was no larger than fifteen and as small as nine, so random selection with such small numbers gives no guarantee that the experimental and control groups will be equivalent). To make things still more uncertain, test scores for children younger than 3 years are poor predictors of later intelligence test scores, and test results for infants at the age of 3 or 6 months are extremely
unreliable. It would therefore be difficult in any case to assess the random placement from early test scores. The debate over the results is ongoing and unresolved as we write.

T
HE
M
ILWAUKEE
P
ROJECT.
The Abecedarian Project was inspired by an earlier attempt to forestall mental retardation in a population of children who were at high risk. The famous Milwaukee Project started in 1966 under the supervision of Richard Heber, a professor at the University of Wisconsin (Madison) who had been research director of President John F. Kennedy’s panel on mental retardation at the beginning of the decade. Healthy babies of poor black mothers with IQs below 75 were almost, but not quite, randomly assigned to no day care at all or day care starting at 3 months and continuing until they went to school. The day care lasted all day, five days a week, all year. The families of the babies selected for day care received a variety of additional services and health care. The mothers were paid for participation, received training in parenting and job skills, and their other young children received free child care. Only thirty-five children are considered to have completed the study, seventeen receiving the special attention and the remainder serving as controls.

Soon after the Milwaukee project began, reports of enormous net gains in IQ (more than 25 points) started appearing in the popular media and in psychology textbooks.
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However, there was a dearth of publication that allowed experts to evaluate the project. The few technical items that appeared raised more questions than they answered.
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It was not until 1988 that another Wisconsin professor associated with the work, Howard Garber, published an interpretable analysis of what had been done in the Milwaukee Project and what was found.
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By the age of 12 to 14 years, the children who had been in the program were scoring about ten points higher in IQ than the controls. Compared to other early interventions, this is a notably large difference. But this increase was not accompanied by increases in school performance compared to the control group. Experimental and control groups were both one to two years retarded in reading and math skills by the time they reached fourth grade; their academic averages and their achievement scores were similar, and they were similarly rated by their teachers for academic competence. From such findings, psychologists Charles Locurto and Arthur Jensen have concluded that the program’s substantial and enduring gain in IQ has been produced by coaching the children
so well on taking intelligence tests that their scores no longer measure intelligence or
g
very well.
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Time will tell whether a more hopeful conclusion can be drawn.

In summary, the two experiments contain some promising leads. But it is not obvious where to go from here, for they differed in possibly important ways. The Abecedarian Project evaluated day care; the Milwaukee Project provided numerous interventions besides day care, including parental payment and training. It is hard to tell whether the former found enduring IQ benefits, given the very early divergence in test scores for experimental and control groups, but it found some academic benefits; the latter found an enduring IQ gain, but has not yet shown comparable intellectual gains in school work. It may be relevant that the Abecedarian mothers had higher IQs than the Milwaukee mothers, so the children may not have been at equal risk for retardation.

Reading this history of interventions, you may have noticed a curious parallelism: In the media, the good news is trumpeted as if there were no ambiguity; in the technical journals, the good news is viewed with deep suspicion and discounted. Are the scholars as excessively nitpicking as the journalists are credulous? Here is the difficult-to-discuss problem that overhangs the interpretation of these results: The people who run these programs want them to succeed. This is hardly a criticism. People who are spending their lives trying to help disadvantaged children ought to be passionately committed to their success. But it is hard for them to turn around and be dispassionate about the question, “How well are we doing?” Often the raw data from these programs are not easily accessible to outside scholars. Not infrequently, when such data finally are made available, they reveal a different and less positive way of viewing the successful results than the one that had previously been published.

Consensus has thus been hard to reach, but progress is being made. In our account, we have avoided dwelling on technical problems that, though perhaps valid, would modify the results only at the margin. When we have alluded to uncertainties and methodological difficulties, we have restricted ourselves to clear potential problems, which, if true, seriously weaken the basis for claiming success. In other words, we have tried to avoid nitpicking. The fact is that we and everyone else are far from knowing whether, let alone how, any of these projects have increased intelligence. We write this pessimistic conclusion knowing how
many ostensibly successful projects will be cited as plain and indisputable evidence that we are willfully refusing to see the light.

There is one sure way to transform a child’s environment beneficially: adoption out of a bad environment into a good one. If adoption occurs at birth, it is at least possible that the potential effects of postnatal environmental disadvantage could be wiped out altogether.
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The specific question now is: How many points does being raised in a good adoptive home add to an IQ score?

Children are not put up for adoption for the edification of social theorists. There are no controlled experiments on the effects of adoption. Adoption usually means trouble in the biological family; trouble usually lands on families nonrandomly and unaccountably, making it hard to extract clear, generalizable data. The most famous studies were mostly done decades ago, when the social and financial incentives for adoption were different from today’s. Legalized contraception and abortion, too, have altered the pool of subjects for adoption studies. Both the environmental and genetic legacies of children put up for adoption have surely changed over the years, but it is impossible to know exactly in what ways and how much. In short, although data are abundant and we will draw some broad conclusions, this is an area in which solid estimates are unlikely to be found.

When Environment Is Decisive

Lest anyone doubt that environment matters in the development of intelligence, consider the rare and bizarre cases in which a child is hidden away in a locked room by a demented adult or breaks free of human contact altogether and runs wild. From the even rarer cases that are investigated and told with care and accuracy, we know that if the isolation from human society lasts for years, rather than for just months, the children are intellectually stunted for life.
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Such was, for example, the experience of the “Wild Boy of Aveyron,” discovered in southern France soon after the Revolution and the establishment of the first French Republic, like an invitation to confirm Rousseau’s vision of the noble savage. The 12- or 13-year-old boy had been found running naked in the woods, mute, wild, and evidently out of contact with humanity for most of his life. But, as it turned out, neither he, nor the others like him that we know about, resemble Rousseau’s noble savage in the least. Most of them never learn to speak properly or to become independent adults. They rarely learn to meet even the lowest standards of personal hygiene or conduct. They seem unable to become fully human despite heroic efforts to restore them to society. From these rare cases we can draw a hopeful conclusion: If the ordinary human environment is so essential for bestowing human intelligence, we should be able to create extraordinary environments to raise it further.
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As a group, adopted children do not score as high as the biological children of their adopting parents.
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The deficit may be as large as seven to ten IQ points. It’s not completely clear what this deficit means. One hypothesis is that the adopted children’s genes hold them back; another is that there is an intellectually depressing effect of adoption itself, or that being placed in adopting homes not immediately after birth (as only some of them are), but only after several months or years, loses the benefit of the nurturing their adopting parents would have provided earlier in their lives.

At the same time, researchers think it very likely that adopted children earn higher scores than they would have had if they been raised by their biological parents, because the adopting home environment is likely to be better than the one their biological parents would have provided. If so, this would be a genuine effect of the home environment. How large is the effect? Charles Locurto, reviewing the evidence and striking an average, concludes that it is about six points.
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As a consensus figure, that seems about right to us. However, a consensus figure is not what we want, as Locurto recognizes. It does not identify how wide a gap separates the environments provided by adopting homes and the homes in which the children would have been reared had they not been adopted. We seek a comparison of the IQs of children growing up in homes of a known low socioeconomic status and genetically comparable children reared in homes of a known high socioeconomic status. What would the increment in IQ look like then?

Two approximations to an ideal adoption study, albeit with very small samples, have recently been done in France.
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In one, Michel Schiff and his colleagues searched French records for children abandoned in infancy, born to working-class (unskilled) parents, who were adopted into upper-class homes. Only thirty-two children met the study’s criteria. In childhood, their average IQ was 107. To understand what this means, two further comparisons are in order. First, the adopted children scored eight points lower on average than their schoolmates, presumably from comparable upper-class homes. This confirms the usual finding with
adopted children. But, second, they scored twelve points higher than twenty of their full or half-siblings who were reared at least for a time by a biological parent or grandparent in lower-class surroundings.
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This study provides a rare chance to estimate roughly where the adoptees would have been had they remained in their original homes.

A second French study compared four small groups of adopted children, reared in either high- or low-SES homes, and the biological offspring of high- or low-SES parents. Thus one could ask, albeit with only a handful of children,
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what happens when children born to low-SES parents are adopted into a high-SES home or when children born to high-SES parents are adopted into low-SES homes; and so on. In this study as well, the switch from low to high status in the home environment produced a twelve-point benefit in IQ.
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Such findings, of course, implicate the home environment as a factor in the development of cognitive ability. We cannot be sure how much, because we do not know exactly how far down the SES ladder the children came from, or how far up the ladder they were moved into their adoptive homes. If the twelve-point shift is produced by a small shift in environment (e.g., a child of a truck driver adopted by the family of a bank clerk), it gives a great deal of hope for the effects of adoption; if it was produced only by a huge shift in the environment (e.g., the child of a chronically unemployed illiterate adopted by the Rothschilds), not so much hope. In general, the more important the environment is in shaping cognitive ability, the larger the impact a given change in environment has on IQ.

To see what the policy implications might be, let us suppose that low-and high-SES homes in the French studies represented the 10th and 90th centiles in the quality of the home environment, respectively. If that were the case, what might be accomplished by moving children from very deprived homes (at the 2d centile, to make the example concrete) to very advantaged ones (98th centile)? The results of the French study imply that such a shift in home environment would produce a benefit of almost twenty IQ points.
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