Kids who are adopted get a boost in IQ

New research has found that children who are adopted have slightly higher IQs than siblings who remained with their biological parents. The study, published in PNAS, was designed to tease apart genetic and environmental influences on intelligence. The results suggest that the education level of the parents who raise the child can have an impact on IQ, but there is still a strong relationship between the intelligence of the child and his or her biological parents.

“Our goal in this study was not to exclude genetic explanations,” write the authors, “but rather to control for them while focusing on a natural experiment involving differences in environmental experiences.”

The researchers focused on men in Sweden, who all take an IQ test at age 18-20 during Swedish military conscription. They identified 436 cases where one male sibling had been adopted while the other sibling had remained with his biological family. They then compared the IQ test results of the siblings, while also factoring in the education levels of both the biological and adoptive families.