Originally Posted by Taylor
When the results reported in one study stand part from the consistent results reported in the body of literature, then attention must be paid to WHY the results contradict the literature. The abecedarian project has generated quite a bit of back and forth on this issue.
Does the Carolina abecedarian early intervention project prevent sociocultural mental retardation?
An assessment is made of the claim that, when compared with a control group, this early intervention project has produced and maintained higher IQs in children who, because they were from economically and socially impoverished homes, were considered to be at high-risk for mild mental retardation. Four cohorts were recruited over a 5-year period, but the experimental group in Cohorts 3 and 4 produced unusually high scores on the Bayley MDI. Differences between experimental and control groups at 60 months of age were comparable to differences at 6 months of age. The assertion that the experimental group's advantage was due to the effects of the first few months of intervention, rather than to the chance allocation of brighter children to the experimental group, is discussed.
Here's another paper which looks at differences at 12 years of age.
Responses are given to Ramey's 10 “substantive amplifications.” The ability test difference between the intervention and control groups at 12 years of age is approximately the same as the difference had been at 6 months of age. This finding remains unexplained. Some of the data are still not forthcoming. I remain unconvinced that the Abecedarian Project provides evidence that quality educational day-care services can prevent mild mental retardation in children who are said to be at risk because they come from economically and socially impoverished homes.
It's difficult to claim that you've raised IQ when the gap between the intervention and control groups remains unchanged between when the project started and when it finished. This criticism would point to Abecedarian Project being consistent with the results found in the existing literature on early childhood intervention.
This was Heckman's conclusion as well. I have no issue with this conclusion.
Still, whether the difference can be truly attributed to a credible boost in intelligence seems to me rather academic. The study has found quite meaningful differences in real-life outcomes as a result of the early intervention. By young adulthood, the treatment group was more likely to maintain education or hold skilled jobs, had a lower incidence of teenage pregancy, and were three times as likely to attend college or university.
In another project Heckman found something similar:
It should be noted that the variance between groups was almost entirely due to early verbal development - talking and reading to kids from a young age. And, as with most of these studies of early intervention, the results only generalize to children of low income, black families.
Understanding The Sources Of Ethnic And Racial Wage Gaps And Their Implications For Policy
Minority deficits in cognitive and noncognitive skills emerge early and then widen. Unequal schooling, neighborhoods, and peers may account for this differential growth in skills, but the main story in the data is not about growth rates but rather about the size of early deficits. Hispanic children start with cognitive and noncognitive deficits similar to those of black children. They also grow up in similarly disadvantaged environments and are likely to attend schools of similar quality. Hispanics complete much less schooling than blacks. Nevertheless, the ability growth by years of schooling is much higher for Hispanics than for blacks. By the time they reach adulthood, Hispanics have significantly higher test scores than do blacks. Conditional on test scores, there is no evidence of an important Hispanic-white wage gap. Our analysis of the Hispanic data illuminates the traditional study of black-white differences and casts doubt on many conventional explanations of these differences since they do not apply to Hispanics, who also suffer from many of the same disadvantages. The failure of the Hispanic-white gap to widen with schooling or age casts doubt on the claim that poor schools and bad neighborhoods are the reasons for the slow growth rate of black test scores.