A study published in the current issue of Journal of Personality studied adult male monozygotic (MZ) and dizygotic (DZ) twins to find that difference in religiousness are influenced by both genes and environment. But during the transition from adolescence to adulthood, genetic factors increase in importance while shared environmental factors decrease. Environmental factors (i.e. parenting and family life) influence a child's religiousness, but their effects decline with the transition into adulthood. An analysis of self-reported religiousness showed that MZ twins maintained their religious similarity over time, while the DZ twins became more dissimilar. "These correlations suggest low genetic and high...