One response to the disappointment of Head Start has been to redefine its goals. Instead of raising intelligence, contemporary advocates say it reduces long-term school failure, crime, and illegitimacy and improves employability.58 These delayed benefits are called sleeper effects, and they are what presumably justify the frequent public assertions that “a dollar spent on Head Start earns three dollars in the future,” or words to that effect.59 But even these claims do not survive scrutiny. The evidence for sleeper effects, such as it is, almost never comes from Head Start programs themselves but from more intensive and expensive preschool interventions.60
PERRY PRESCHOOL. The study invoked most often as evidence that Head Start works is known as the Perry Preschool Program. David Weikart and his associates have drawn enormous media attention for their study of 123 black children (divided into experimental and control groups) from the inner city in Ypsilanti, Michigan, whose IQs measured between 70 and 85 when they were recruited in the early 1960s at the age of 3 or 4.61 Fifty-eight children in the program received cognitive instruction five half-days62 a week in a highly enriched preschool setting for one or two years, and their homes were visited by teachers weekly for further instruction of parents and children. The teacher-to-child ratio was high (about one to five), and most of the teachers had a master’s degree in appropriate child development and social work fields. Perry Preschool resembled the average Head Start program as a Ferrari resembles the family sedan.
The fifty-eight children in the experimental group were compared with another sixty-five who served as the control group. By the end of their one or two years in the program, the children who went to preschool were scoring eleven points higher in IQ than the control group. But by the end of the second grade, they were just marginally ahead of the control group. By the end of the fourth grade, no significant difference in IQ remained.63 Fadeout again.
Although this intensive attempt to raise intelligence failed to produce lasting IQ gains, the Ypsilanti group believes it has found evidence for a higher likelihood of high school graduation and some post-high school education, higher employment rates and literacy scores, lower arrest rates and fewer years spent in special education classes as a result of the year or two in preschool. The effects are small and some of them fall short of statistical significance.64 They hardly justify investing billions of dollars in run-of-the-mill Head Start programs.
OTHER LONGITUDINAL STUDIES OF PRESCHOOL PROGRAMS. One problem faced by anyone who tries to summarize this literature is just like that faced by people trying to formulate public policy. With hundreds of studies making thousands of claims, what can be concluded? We are fortunate to have the benefit of the efforts of a group of social scientists known as the Consortium for Longitudinal Studies. Initially conceived by a Cornell professor, Irving Lazar, the consortium has pulled together the results of eleven studies of preschool education (including the Perry Preschool Project), chosen because they represent the best available scientifically.65 None of them was a Head Start program, but a few were elaborations of Head Start, upgraded and structured to lend themselves to evaluation, as Head Start programs rarely do. The next figure summarizes the cognitive outcomes in the preschool studies that the consortium deemed suitable for follow-up IQ analysis. The reported changes control for pretest IQ score, mother’s education, sex, number of siblings, and father presence.
Soon after completing one of these high-quality experimental preschool programs, the average child registers a net gain in IQ of more than seven IQ points, almost half a standard deviation. The gain shrinks to four to five points in the first two years after the program, and to about three points in the third year.66 The consortium also collected later follow-up data that led the researchers to conclude that “the effect of early education on intelligence test scores was not permanent.”67
Intensive Interventions for Children at Risk of Mental Retardation
The preschool programs we have just described were targeted at disadvantaged children in general. Now we turn to two studies that are more intensive than even the ones analyzed by the consortium and deal with children who are considered to be at high risk of mental retardation, based on their mothers’ low IQs and socioeconomic deprivation.
IQ gains attributable to the Consortium preschool projects
Source: Lazar and Darlington 1982, Table 15.
A case can be made for expecting interventions to be especially effective for these children, since their environments are so poor that they are unlikely to have had any of the benefits that a good program would provide. Moreover, if the studies have control groups and are reasonably well documented, there is at least a hope of deciding whether the programs succeeded in forestalling the emergence of retardation. We will briefly characterize the two studies approximating these conditions that have received the most scientific and media attention.
THE ABECEDARIAN PROJECT. The Carolina Abecedarian Project started in the early 1970s, under the guidance of Craig Ramey and his associates, then at the University of North Carolina.68 Through various social agencies, they located pregnant women whose children would be at high risk for retardation. As the babies were born, the ones with obvious neurologic disorders were excluded from the study, but the remainder were assigned to two groups, presumably randomly. In all, there were four cohorts of experimental and control children. Both groups of babies and their families received a variety of medical and social work services, but one group of babies (the “experimentals”) went into a day care program. The program started when the babies were just over a month old, and it provided care for six to eight hours a day, five days a week, fifty weeks a year, emphasizing cognitive enrichment activities with teacher-to-child ratios of one to three for infants and one to four to one to six in later years, until the children reached the age of 5. It also included enriched nutrition and medical attention until the infants were 18 months old.69 The Abecedarian Project is the apotheosis of the day care approach. This is extremely useful from a methodological perspective: Even if the nation cannot afford to supply the same services to the entire national population of children who qualified for the Abecedarian Project, it serves as a way of defining the outer limit of what day care can accomplish given the current state of the art.
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.70
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.71 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 resu
lts is ongoing and unresolved as we write.
THE MILWAUKEE PROJECT. 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.72 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.73 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.74
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.75 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.
CHANGING THE ENVIRONMENT AT BIRTH
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.76 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.77 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.78
As a group, adopted children do not score as high as the biological children of their adopting parents.79 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.80 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.81 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.82 This study provides a rare chance to estimate roughly where the adoptees would have been had they remained in their original homes.
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