Kids adopted late reap IQ increases.
As in the general population, genes influence the IQ ranking of these late-adopted kids, say psychologist Michel Duyme of the University of Paris VII and his colleagues. For preschoolers scoring below the normal range on intelligence tests, however, adoptive-family environments foster IQ surges that, on average, put the child near or squarely within the normal range, the researchers report.
"Our results show that the adoptive environment for children adopted after 4 years of age is effective in boosting low IQs," Duyme's group concludes in the July 20 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.
Much current research examines genetic influences on intelligence (SN: 5/9/98, p. 292; 6/7/97, p. 349). In contrast, Duyme and his coworkers examine the extent to which children's surroundings influence their intellect. In a prior study, they found that children adopted before age 1 into high-income families displayed particularly large IQ gains by adolescence.
The new study expanded on that work. Using data from seven French public adoption agencies, the researchers identified 65 children who had been adopted between ages 4 and 6 and had received institutional or foster care because they had been abused or neglected as infants.
Just before adoption, the youngsters had an average IQ of 77, with no scores above 86. The IQ range classified as normal runs from 90 to 110.
When tested in early adolescence--mostly ages 13 and 14--the average IQ score of all the adoptees was 91. Average IQ reached 86 for those in low-income homes, 94 for those in mid-income homes, and 98 for those in high-income homes. The researchers say they don't know whether these IQ gains will last into adulthood.
"They've done a nice job of showing that IQ is malleable and that it responds to the kind of environments adopted children go into," says psychologist Robert J. Sternberg of Yale University. Sternberg views IQ as a measure of analytic intelligence, distinct from what he calls practical and creative intelligence.
Psychologist John C. Loehlin of the University of Texas at Austin also sees the new study as evidence for environmental influences on IQ. But other data suggest that such gains decline at later ages, says Loehlin, who views IQ, especially a statistical component known as g, as the core sign of a person's intelligence.
Linda S. Gottfredson, a sociologist at the University of Delaware in Newark and also a g advocate, says that abusive care during infancy may have deflated IQ scores of the French children, who then recovered their true IQs after adoption. Thus, the findings don't show whether the environment would affect the IQs of kids receiving at least adequate care, she argues.
While seeing value in studying environmental effects on intelligence, psychologist Peter H. Schonemann of Purdue University in West Lafayette, Ind., argues that neither IQ nor g provide insight into mechanisms of intelligence.