... Studies of how the environment influences one ability often measured by IQ tests, namely language, have provided some of the new evidence. Vocabulary, in particular, is a common component of IQ tests. Until the early 1990s, the wide variation in people's vocabularies was largely attributed to differences in people's inborn abilities to learn language. But then Huttenlocher and her colleagues decided to systematically study what role an environmental input--speech by a young child's mother--might play in building the child's vocabulary. To test this, Huttenlocher's team taped many hours of chatter between 22 toddlers and their mothers during the children's typical daily activities.
The researchers did the tapings every 2 to 4 months when the children's language skills were developing most rapidly, between 16 and 26 months of age. From the tapes, the researchers detected a remarkable parallel between the size of a child's vocabulary at 26 months and the talkativeness of his or her mother. At the extremes, the mothers varied 10-fold in how much they talked, and the toddler of the most talkative mother had a vocabulary more than four times the size of the vocabulary of the child of the quietest mother.
Of course, the correlation might result at least partly from genes for verbal ability shared by mother and child. But that's unlikely to be the primary cause, says Huttenlocher, because the moms in the study did not differ much in verbal IQ. What's more, the children were clearly picking up their vocabularies from their mothers, because the words each child used the most frequently mirrored those favored by the mother, and the mothers differed very little in the relative frequency with which they used various words. ...
In 1972, Ramey, his wife Sharon, and their colleagues started the Abecedarian preschool intervention program at UNC, which began at infancy and lasted 5 years. For the project, the researchers randomly assigned 111 children from poor and uneducated families in the surrounding community to either an intervention group, which received full-time, year-round day care along with medical and social-work services, or a control group getting medical and social benefits but no day care. ...
The success of the endeavor, and its ability to mold IQ, was evident by the time the children were 3 years old. The toddlers in the program showed normal IQs averaging 101, a whopping 17-point advantage over the average IQs of the controls. Follow-up results, to be reported in an upcoming issue of Applied Developmental Science, demonstrate that the effects are long-lasting. More than a decade later, at age 15, children from the intervention group still maintained an IQ advantage of five points over controls, with respective averages of 97.7 and 92.6. They also did better on standardized tests of reading and math and were less likely, by nearly a factor of 2, to have been held in the same grade in school for a second year. ...
... For now, the evidence strongly suggests that quality preschooling by any standard would provide an important safety net for children who might otherwise not get the mental stimulation they need. The price tag is steep--more than $10,000 per child per year. But the payback in productivity, and in reduced social support programs later in life, may be even greater, if national preschool programs accrue a benefit similar to that seen in North Carolina--something now being tested by a 200-site, Early Head Start program in which infants are enrolled right after birth. ...
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