Mar 24, 2015 08:18 PM EDT By Staff Reporter, UniversityHerald Reporter

New research suggests that young adults who were raised in educated households develop higher cognitive ability than those who were brought up in less ideal environments.

Researchers at the University of Virginia and Lund University in Sweden found that environmental influences play a significant role in cognitive ability as measured in early adulthood. The study does not refute previous findings that DNA impacts intelligence.

The study compared the cognitive ability - as measured by IQ - of 436 Swedish male siblings in which one member was reared by biological parents and the other by adoptive parents. The IQ of the adopted males, which was measured at ages 18-20, was 4.4 points higher than their nonadopted siblings.

"In Sweden, as in most Western countries, there is a substantial excess of individuals who wish to adopt compared to adoptive children available," first author Kenneth S. Kendler, said in a statement. "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 more educated and in better socioeconomic circumstances than the biological parents. 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 IQ. In the rare circumstances when the biological parents were more educated than the adoptive parents, the cognitive ability of the adopted-away offspring was lower than the one who was reared by the genetic parents.

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 naïve 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."

The findings are detailed in the journal Proceedings of the National Academy of Sciences.

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