Eaves Lindon, Foley Debra, Silberg Judy
Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298-0003, USA.
Twin Res. 2003 Dec;6(6):486-9. doi: 10.1375/136905203322686473.
A recurring criticism of the twin method for quantifying genetic and environmental components of human differences is the necessity of the so-called "equal environments assumption" (EEA) (i.e., that monozygotic and dizygotic twins experience equally correlated environments). It has been proposed to test the EEA by stratifying twin correlations by indices of the amount of shared environment. However, relevant environments may also be influenced by genetic differences. We present a model for the role of genetic factors in niche selection by twins that may account for variation in indices of the shared twin environment (e.g., contact between members of twin pairs). Simulations reveal that stratification of twin correlations by amount of contact can yield spurious evidence of large shared environmental effects in some strata and even give false indications of genotype x environment interaction. The stratification approach to testing the equal environments assumption may be misleading and the results of such tests may actually be consistent with a simpler theory of the role of genetic factors in niche selection.
对用于量化人类差异的遗传和环境成分的双胞胎方法的一种反复出现的批评是所谓“等环境假设”（EEA）的必要性（即同卵双胞胎和异卵双胞胎经历同等相关的环境）。有人提议通过按共享环境量的指标对双胞胎相关性进行分层来检验EEA。然而，相关环境也可能受到遗传差异的影响。我们提出了一个关于双胞胎在生态位选择中遗传因素作用的模型，该模型可能解释双胞胎共享环境指标的变化（例如，双胞胎对成员之间的接触）。模拟结果表明，按接触量对双胞胎相关性进行分层可能在某些层次上产生关于大的共享环境效应的虚假证据，甚至给出基因型与环境相互作用的错误指示。检验等环境假设的分层方法可能会产生误导，而且此类检验的结果实际上可能与遗传因素在生态位选择中作用的更简单理论一致。
