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标题：Family environment and the malleability of cognitive ability: A Swedish national home-reared and adopted-away cosibling control study
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作者：Kenneth S. Kendler ; Eric Turkheimer ; Henrik Ohlsson 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：15
页码：4612-4617
DOI：10.1073/pnas.1417106112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceIndividual 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. Cognitive ability strongly aggregates in families, and prior twin and adoption studies have suggested that this is the result of both genetic and environmental factors. In this study, we used a powerful design--home-reared and adopted-away cosibling controls--to investigate the role of the rearing environment in cognitive ability. We identified, from a complete national Swedish sample of male-male siblings, 436 full-sibships in which at least one member was reared by one or more biological parents and the other by adoptive parents. IQ was measured at age 18-20 as part of the Swedish military service conscription examination. Parental educational level was rated on a 5-point scale. Controlling for clustering of offspring within biological families, the adopted siblings had an IQ 4.41 (SE = 0.75) points higher than their nonadopted siblings. Each additional unit of rearing parental education was associated with 1.71 (SE = 0.44) units of IQ. We replicated these results in 2,341 male-male half-sibships, in which, controlling for clustering within families, adoption was associated with a gain of IQ of 3.18 (SE = 0.34) points. Each additional unit of rearing parental education was associated with 1.94 (SE = 0.18) IQ units. Using full- and half-sibling sets matched for genetic background, we found replicated evidence that (i) rearing environment affects IQ measured in late adolescence, and (ii) a portion of the IQ of adopted siblings could be explained by the educational level of their adoptive parents.
关键词：cognitive ability ; environment ; adoption ; rearing ; cosibling control