IQ Study Weighs Genes,Environment
Children growing up in middle-class and wealthy families may not benefit much from all those classical-music CDs, interactive books, and exclusive preschool programs meant to boost a young child's brainpower. But early intervention in the home and in the classroom can make a big difference for a child born into extreme poverty, according to a soon-to-be-published study.
Led by Eric Turkheimer, a psychologist at the University of Virginia in Charlottesville, the study concludes that while genetic makeup explains most of the differences in IQ for children in wealthier families, environment—and not genes—makes a bigger difference for minority children in low-income homes.
Specifically, what researchers call "heritability"—the degree to which genes influence IQ—was significantly lower for poor families, 0.1 on a scale of zero to 1, than it was for those at the higher end of the income spectrum, for whom it was 0.72.
"Once you're put into an adequate environment, your genes start to take over," Mr. Turkheimer said in an interview last week. But in poor environments, "genes don't have that ability."
Mr. Turkheimer said his findings do not back up any particular program or intervention strategy. But the study, which is to be published in the November issue of the journal Psychological Science, does suggest that spending on Head Start and other high-quality programs for children of low socioeconomic status are worthwhile, he said.
"Money spent on improving environments is best spent on improving the worst environments," he said.
By the same token, he said, spending money in schools where students are already doing well "isn't going to have the same bang for the buck as taking schools that are very bad and making them OK."
Looking at Twins
To conduct the research, Mr. Turkheimer and his colleagues analyzed data from the National Collaborative Perinatal Project, a study conducted by the federal government from 1959 to 1974.
The sample included close to 50,000 pregnant women, mostly African- American and living near or below the poverty line. Because the sample was so large, more than 600 pairs of twins were born.
Seven years later, the researchers administered the Wechsler Intelligence Scale for Children to 319 pairs of the twins, with 114 of them being identical twins and the rest fraternal. Those test scores were used to estimate the children's IQ levels.
Looking at the differences in traits between identical and fraternal twins allows researchers to isolate characteristics based on genetics. But such research has been limited, because few twin studies include children from poor families.
The sizable sample of twins in the University of Virginia study, combined with new statistical models for studying the effects of socioeconomic status, allowed Mr. Turkheimer to arrive at his results.
"Although there is much that remains to be understood, our study and the ones that have preceded it have begun to converge on the hypothesis that the developmental forces at work in poor environments are qualitatively different than those at work in adequate ones," according to an advance copy of Mr. Turkheimer's Psychological Science article.
Revisiting The Bell Curve
Mr. Turkheimer's research revisits what he and the other primary author of the article, Irving I. Gottesman, a psychology professor at the University of Minnesota Medical School in Minneapolis, call "the fractious history of scientific investigations of the heritability of intelligence."
A key moment in that history occurred in 1994 when the book called The Bell Curve was published. In it, authors Richard J. Herrnstein and Charles Murray suggested that genes explain most of the differences in cognitive ability.
By offering support for the notion that African-Americans were intellectually inferior to whites and other races—and that education or other interventions were largely powerless to change that—the book drew sharp criticism and charges of racism.
Reached by e-mail last week, Mr. Murray, a political scientist who is now a senior fellow at the American Enterprise Institute, a Washington think tank, said he was not ready to comment on Mr. Turkheimer's research and "needed more time to digest" the findings.
Krista Kafer, a senior policy analyst at the Washington-based Heritage Foundation, said she thought using the new research to justify spending on Head Start and other programs was "too much of a leap."
"It's using science for advocacy," she said, adding that she could use the same findings to argue in favor of giving low-income families school choice.
'A Wake-Up Call'
Others welcomed what they see as the implications of the study.
The new study confirms "the philosophy that experience and environment account for a lot of the variabilities" in children, said Jeffrey Seltzer, a child psychologist working with the Montgomery County, Md., school district's Head Start and pre-K programs. "It's great that they have research now to back this up, but this is certainly the assumption that I've been working under."
Jane Knitzer, the acting director of the National Center for Children in Poverty, located at Columbia University, said that the study "challenges the myth that investing in social programs is a waste of money."
She added that while the concept of "universal" preschool for young children is an important development, the research shows that special attention needs to be paid to enriching experiences for the poorest children.
"In this current fiscal climate that we're in, I think it's a wake- up call to be cautious about what we unravel," she said.
Mr. Turkheimer added that it is important for more researchers to "include very poor children in analyses of genes and environment."
And he noted that all of the mandated achievement testing being conducted in schools could be used for more than just holding schools accountable for results. "It's a fabulous research base," he said.
Vol. 23, Issue 2, Pages 1, 16-17Published in Print: September 10, 2003, as IQ Study Weighs Genes, Environment