From: rhinoceros (rhinoceros@freemail.gr)
Date: Tue Sep 02 2003 - 15:10:27 MDT
From the Washington Post
Genes' sway over IQ may vary with class
Study: Poor More Affected by Environment
http://www.washingtonpost.com/ac2/wp-dyn/A12059-2003Sep1
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"How many books are in the home and how good the teacher is may be questions to consider for a middle-class child, but those questions are much more important when we're talking about children raised in abject poverty," said lead researcher Eric Turkheimer, a psychologist at the University of Virginia.
The work, to be published in the November issue of the journal Psychological Science, is part of a new wave of research that embraces a more dynamic view of the relationship between genes and environment. Although older research treated nature and nurture as largely independent and additive factors, and saw people as the sum of their genetic endowments and environmental experiences, the emerging view allows that genes can influence the impact of experiences and experiences can influence the "expression," or activity levels, of genes.
In Turkheimer's study, the impact of genes on IQ varied depending on a child's socioeconomic status (SES), a sociological measure that includes household income and other elements of class and social status.
Until recently, Turkheimer and others said, research had indicated that the "heritability" of IQ -- that is, the degree to which genes can explain the differences in IQ scores -- completely dominated environmental influences. That led some to call into question the value of programs such as Head Start, which are based on the assumption that by improving the childhood environment through extra attention, nutrition and care, a child's intellectual future could be improved.
But it turned out that virtually all those studies on the heritability of IQ had been done on middle-class and wealthy families. Only when Turkheimer tested that assumption in a population of poor and mostly black children did it become clear that, in fact, the influence of genes on IQ was significantly lower in conditions of poverty, where environmental deficits overwhelm genetic potential.
"This paper shows how relevant social class is" to children's ability to reach their genetic potential, said Sandra Scarr, a professor emerita of psychology now living in Hawaii, who did seminal work in behavioral genetics at the University of Virginia.
Specifically, the heritability of IQ at the low end of the wealth spectrum was just 0.10 on a scale of zero to one, while it was 0.72 for families of high socioeconomic status. Conversely, the importance of environmental influences on IQ was four times stronger in the poorest families than in the higher status families.
"This says that above a certain level, where you have a wide array of opportunities, it doesn't get much better" by adding environmental enhancements, Scarr said. "But below a certain level, additional opportunities can have big impacts."
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