Education-and not just genes-affect your I.Q., according to a study that compared the intelligence test scores of Swedish twins raised in different environments. The project compared scores of 436 twin brothers of which one was reared by biological parents and another by adoptive parents. The adoptees, tested at ages 18 to ...

Education-and not just genes-affect your I.Q., according to a study that compared the intelligence test scores of Swedish twins raised in different environments.

The project compared scores of 436 twin brothers of which one was reared by biological parents and another by adoptive parents. The adoptees, tested at ages 18 to 20, showed I.Q.'s 4.4 points higher than their nonadopted siblings, according to the findings.

The researchers say that's probably because adopting parents tend to provide better education than biological parents. That in turn occurs because adoption agencies can afford to be selective in choosing parents with whom to place children-because would-be adopters outnumber available adoptees.

The findings were published online in the Early Edition of the journal Proceedings of the National Academy of Sciences on March 23.

“In Sweden, as in most Western countries, there is a substantial excess of individuals who wish to adopt compared to adoptive children available,” said co-author Kenneth S. Kendler of Virginia Commonwealth University. “Therefore, adoption agencies see it as their goal of selecting relatively ideal environments within which to place adoptive children.”

The adoptive parents in the study tended to be both more educated and in better socioeconomic circumstances than the biological parents, the authors said. In the study, parental education level was rated on a five-point scale; each additional unit of education by the rearing parents was associated with 1.71 more units of I.Q.

In the rare cases when the biological parents were more educated than the adoptive parents, the effect was the opposite and the adopted offspring showed the lower I.Q., the investigators added.

Previous studies have found that educated parents are more likely to talk at the dinner table, take their children to museums and read stories to their children at night.

“We're not denying that cognitive ability has important genetic components, but it is a na�ve idea to say that it is only genes,” Kendler said. “This is strong evidence that educated parents do something with their kid that makes them smarter and this is not a result of genetic factors.”

Co-author Eric Turkheimer, also of the university, authored a study in 2003 indicating that the effect of genes on I.Q. depends on socioeconomic status. He said the most recent study further affirms that.

“Differences among people in their cognitive ability are influenced by both their genes and environments, but genetic effects have often been easier to demonstrate because identical twins are essentially clones and have highly similar I.Q.'s,” Turkheimer said.

“Many studies of environmental effects on cognitive ability are based on special programs like Head Start that children are placed in for a limited amount of time,” he added. “These programs often have positive results while the program is in place, but they fade quickly when it is over. Adoption into a more educated household is the most permanent kind of environmental change, and it has the most lasting effects.”

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wscience, "Well-educated parents improves kids� IQ levels", MachPrinciple, March 28, 2015, https://machprinciple.com/post/well-educated-parents-improves-kids-iq-levels