Rearing Environmental Influences on Religiousness: An Investigation of Adolescent Adoptees

Abstract

Religiousness is widely considered to be a culturally transmitted trait. However, twin studies suggest that religiousness is genetically influenced in adulthood, although largely environmentally influenced in childhood/adolescence. We examined genetic and environmental influences on a self-report measure of religiousness in a sample consisting of 284 adoptive families (two adopted adolescent siblings and their rearing parents); 208 biological families (two full biological adolescent siblings and their parents); and 124 mixed families (one adopted and one biological adolescent sibling and their parents). A sibling-family model was fit to the data to estimate genetic, shared environmental, and nonshared environmental effects on religiousness, as well as cultural transmission and assortative mating effects. Religiousness showed little evidence of heritability and large environmental effects, which did not vary significantly by gender. This finding is consistent with the results of twin studies of religiousness in adolescent and preadolescent samples.

Figure 1

A sibling-family model showing one biological and one adopted sibling. The model includes genetic (a), shared environmental (c), nonshared environmental (e) effects. Assortative mating was modeled in terms of a co-path (D) between the parents' phenotypes. The sibling shared environment is modeled as an effect of mother's (m) and father's (f) religiousness, as well as a sibling-specific residual effect (B). The existence of the cultural transmission paths (m and f) as well as assortative mating (D) induces a correlation between additive genetic and shared environmental effects (the A-C covariance; the same correlation exists in the offspring generation but is not depicted for convenience).