Hostility and Nonshared Family Environment: A Study of Monozygotic Twins

Abstract

A sample of 25 adult male monozygotic (Mz) twin pairs completed the Cook and Medley Hostility scale, and Structural Analysis of Social Behavior measures of their parents′ behavior toward them during childhood. Results indicated that high levels of hostile control and low levels of positive involvement from parents were associated with high levels of self-reported hostility. To rule out possible genetic influences on this covariation between parental behavior and hostility, co-twin difference scores for hostility and parental behavior were computed and correlated. The more hostile Mz co-twin described his parents as exhibiting a greater degree of hostile control. Thus, nongenetic variance in hostility was associated with perceived differences in early environments. Implications for the development of hostility and its association with health are discussed.