Data for the current study were taken from the Minnesota Twin Family Study, a longitudinal investigation of reared together twins and their parents (Iacono, Carlson, Taylor, Elkins, & McGue, 1999), focused primarily on the etiology of substance use disorders, and related forms of psychopathology. Although the Minnesota Twin Family Study included both male and female twins, the females were not asked to complete the psychopathy measure used in the current study; hence, this report deals only with the male participants. Data used in the present study was collected from a cohort of adolescent male twins (N = 315) born between the years 1972–1978, and identified via Minnesota public birth records and recruited for participation the year the twins turned 17-years-old. Among eligible families identified during recruitment, 83% agreed to participate. Parents of participating and non-participating families were not found to differ in terms of rates of psychopathology or SES (Iacono et al., 1999). Twin families were excluded from participation if either twin had a cognitive or physical disability that would hinder their participation in the day-long, in-person assessment, or if
