Abstract

A 51-item fear survey was administered to more than 2,600 adolescents and adults, including m ore than 400 pairs of like-sex twins, to examine developmental patterns and genetic influences on common fears. Raw data were age-sex standardized and subjected to factor analysis, and preliminary analyses of the factor scores documented both age and genetic effects. Some fears habituate with age; others exhibit sensitization; and, for some fears, intensity is uniform across development. Genetic effects were found for all factors, but the magnitude of such effects varied. Based on these initial analyses, developmental patterns of genetic and environmental influences on self-assessed fears were examined in 354 pairs of like-sex twins, ages 14-34. Hierarchical multiple regression was used to predict a twin's fearfulness from the co-twin's fear, the age and zygosity of the twin pair, and the interactions of these 3 predictors. For all fear factors, co-twin's score and the interaction of co-twin's score with pair zygosity significantly contributed to the prediction of a twin's fearfulness, but the magnitude of both effects varied for different fears. For 2 fear factors, Personal Death and Loved One's Misfortunes, 3-way interactions of co-twin's score, age, and zygosity were observed. The findings suggest significant genetic modulation of developmental patterns in the acquisition and maintenance of some adaptive fears.