To test our hypothesis that the genetic and environmental influences on internalizing pathology differ as a function of marital quality, we needed to utilize a model that allowed the variance components of internalizing to vary as a function of marital quality. This type of analysis has been referred to as a test of “gene-environment interaction,” or the notion that different environments can lead to different genetic expression of a phenotype. However, this term does not completely describe the nature of the effects we examined. In the current study, neither the moderator variable, marital quality, nor the dependent variable, internalizing pathology, are wholly “environmental” or wholly “genetic.” The advantage of the model that we utilize is that it is possible to decompose the moderator variable into its genetic and environmental variance components, and test for gene-environment interaction in the presence of gene-environment correlation (Purcell, 2002). A genetic correlation is the amount of overlap in the genetic influences on two phenotypes and ranges from −1 to +1; similar types of correlations (i.e., overlap) can occur for shared and nonshared environmental influences. Therefore,
