For the present report, data were collected when members of both cohorts were at a similar age, specifically, the intake assessment for the 17-year-old cohorts (males: M=17.5, SD=0.4; females: M=17.5, SD=0.5) and the second follow-up assessment for the 11-year old cohorts (males: M=18.0, SD=0.7; females: M=18.3, SD=0.7). All study protocols and data collection methods remained consistent across the intake and second follow-up assessments. The current report included those participants for whom data on the psychophysiological measures of interest (see below for details) were available: 303 MZ and 153 DZ male twin pairs, 331 MZ and 182 DZ female twin pairs. Consistent with the demographics of Minnesota during the years the twins were born, almost all are Caucasian (98%). Written informed assent or consent (from the participant or from the parent of a minor child) was obtained as appropriate.
