As most adults will marry at least once during their lifetime, studying marital quality and its predictors is of great importance. The current study addresses (a) the extent of agreement between husbands and wives on their marital quality, (b) genetic and environmental sources of individual differences on spouse reports of marital quality, and (c) the extent to which genetic and environmental influences account for overlap of spouse reports on marital quality. Adult Swedish twin women and their partners participated in this study. Genotype-environment (GE) correlations were found for marital quality, suggesting that wives' genetically influenced characteristics set a tone for the marriage. Wives' genetically influenced characteristics also accounted for overlap of spouse reports of marital quality. Finally, nonshared environmental influences were the primary contributor to both individual reports and the overlap of spouse reports, an interesting deviation from findings of behavior genetic studies of other types of relationships.

The knowledge we have of childhood and adolescent behaviour is, to some extent, a function of the unique perspective of the rater. Although many behavioural genetics studies have used parent and child self-reports in their assessments of child and adolescent adjustment, few have included teacher ratings of behaviour. It is possible that genetic and environmental contributions to teacher reports are different from those using parent and self-reports. The present study examined genetic and environmental influences on six subscales of the Child Behavior Checklist Teacher Report Form (CBC-TRF) using a normative sample of adolescents. The sample consisted of 373 same-sex twin and sibling pairs of varying degrees of genetic relatedness participating in the Nonshared Environment in Adolescent project (NEAD). For all of the CBC subscales, except attention problems and social problems, nonshared environmental influence was the most important source of variance. Additive genetic factors were of moderate importance for externalising behaviours, whereas nonadditive genetic factors contributed to the anxious/depressed, attention problems, withdrawn, and social problems subscales. For none of the constructs was shared environment a significant influence. Three alternative models testing for contrast effects, differences in twin and nontwin siblings, and differences in nondivorced and stepfamilies were examined. In most cases, the best-fitting model was a model that did not include any of these effects, suggesting that these factors do not critically affect the basic model. However, some of the patterns of correlations and parameter estimates were unusual and may warrant future investigation.

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Findings from decades of research show that the environmental experiences of individuals reared in the same home can make them different from one another as well as similar. This is true for a wide range of individual characteristics and personal relationships. The phenomenon in which environmental influences cause family members to differ from one another is known in the behavioral genetic literature as nonshared environment.