The importance of environment on cognitive ability

11 May

Adoption is the closest thing we have to licensed parenting, in most jurisdictions a potential parent is screened by some agency before being allowed to adopt. In situations where one child is adopted and a sibling remains with the biological parent we have the conditions for a natural experiment – a test of the importance of effects of nurture on cognitive ability.

A study published this year analyses 436 such cases. From the paper:

“Individual differences in cognitive ability result from a complex admixture of genetic and environmental influences. Adopted children are one way to estimate the degree of malleability of cognitive ability in response to environmental change in the context of a scientific design that can control for genetic differences among individuals. Sibling pairs in which one member is adopted away and the other reared by biological parents are a particularly powerful research design. In a large population-based sample of separated siblings from Sweden, we demonstrate that adoption into improved socioeconomic circumstances is associated with a significant advantage in IQ at age 18. We replicate the finding in a parallel sample of half-siblings.”

 

2 Responses to “The importance of environment on cognitive ability”

  1. khrabik May 16, 2015 at 2:12 pm #

    A flaw in this study is the assumption that siblings have similar cognitive ability and the independent variable is the enviornment. A better study would be one in which idential twins were reared in different enviornments. There is an intersting book by Lawrence Wright called Twins. Although it is old and there may be more information out there that sheds light on the subject, you walk away with the conclusion that nature is a stronger pull than nuture.

    • jecgenovese May 18, 2015 at 6:07 pm #

      Not really a flaw in the study, but a limitation. Siblings who are not identical twins share 50% of their genes and, thus, you would not expect them to be as similar as identical twins raised apart. But you would expect them to be more similar than unrelated individuals raised apart.

      Thank you for your comment!

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