Sundet Jon Martin, Eriksen Willy, Tambs Kristian
Institute of Psychology, University of Oslo, Norway.
Psychol Sci. 2008 Sep;19(9):843-7. doi: 10.1111/j.1467-9280.2008.02166.x.
Research on twins and unrelated persons living together indicates that, although differences in intelligence between persons are caused by both genetic and environmental factors, similarities--and especially those between adults--are mostly or exclusively due to shared genes. However, twin and adoption designs have been criticized for incorrectly estimating the effects of the environment on the similarity between relatives, and studies of environmental effects in other family constellations may be enlightening. In a sample comprising more than 334,000 pairs of brothers (ages 18-21 years) who were tested at the mandatory conscription for military service in Norway, correlations between brothers' intelligence-test scores decreased with increasing age difference between the brothers. This result indicates that family environmental factors have an impact on the intelligence of young adults. Analyses of subgroups defined by family size and parental education demonstrated that the effects of age difference are essentially independent of these factors.
对双胞胎和共同生活的非亲属的研究表明，尽管人与人之间智力的差异是由基因和环境因素共同造成的，但相似性——尤其是成年人之间的相似性——大多或完全归因于共享基因。然而，双胞胎和收养研究设计因错误估计环境对亲属间相似性的影响而受到批评，对其他家庭组合中环境影响的研究可能会有所启发。在一个由超过33.4万对兄弟（年龄在18至21岁之间）组成的样本中，这些兄弟在挪威义务兵役征兵测试中接受了测试，兄弟间智力测试分数的相关性随着兄弟间年龄差的增加而降低。这一结果表明家庭环境因素对年轻人的智力有影响。按家庭规模和父母教育程度定义的亚组分析表明，年龄差的影响基本上独立于这些因素。
