Horwitz Allan V, Videon Tami M, Schmitz Mark F, Davis Diane
Institute for Health, Health Care Policy, and Aging Research, 30 College Ave., Rutgers University, New Brunswick, N.J. 08901-1293, USA.
J Health Soc Behav. 2003 Jun;44(2):111-29.
A central sociological problem is the extent to which genetics and the environment influence human behavior. Studies of twins are a core method in attempts to disentangle and to determine the comparative strength of genetic and environmental influences on psychosocial outcomes. A critical assumption of twin studies is that both monozygotic "identical" twins and dizygotic "fraternal" twins share common social environments. Therefore, any greater similarity of monozygotic than dizygotic twins is attributed to genetic influences. This paper tests the equal environment assumption by examining the extent to which greater concordance of adolescent monozygotic compared to dizygotic twins results from social, as well as genetic, influences. Bivariate comparisons indicate that monozygotic twins show greater similarity than dizygotic twins in socially-based characteristics including physical attractiveness, time spent in each other's company, the overlap in friendship networks, and friends' use of alcohol. Multivariate analyses indicate that measures of the social environment sometimes reduce or eliminate apparent genetic effects. In comparison with genetic indicators, social variables are usually stronger predictors of depression and alcohol use and abuse. These findings suggest that past twin studies could overstate the strength of genetic influences because some similarities in behavior among monozygotic compared to dizygotic twins stem from social influences.
一个核心的社会学问题是基因和环境在多大程度上影响人类行为。双胞胎研究是试图厘清并确定基因和环境对心理社会结果影响的相对强度的核心方法。双胞胎研究的一个关键假设是，同卵（“ identical”）双胞胎和异卵（“fraternal”）双胞胎都共享共同的社会环境。因此，同卵双胞胎比异卵双胞胎表现出的任何更大相似性都归因于基因影响。本文通过研究与异卵双胞胎相比，青少年同卵双胞胎更高的一致性在多大程度上是由社会影响以及基因影响导致的，来检验等环境假设。双变量比较表明，同卵双胞胎在基于社会的特征上比异卵双胞胎表现出更大的相似性，这些特征包括外表吸引力、彼此相处的时间、友谊网络的重叠以及朋友的饮酒情况。多变量分析表明，社会环境的测量有时会减少或消除明显的基因效应。与基因指标相比，社会变量通常是抑郁以及酒精使用和滥用更强的预测因素。这些发现表明，过去的双胞胎研究可能高估了基因影响的强度，因为同卵双胞胎与异卵双胞胎之间行为上的一些相似性源于社会影响。
