Statistical analyses were performed using SPSS 21.0 (IBM Corporation, Armonk, NY). Prevalence rates of externalizing diagnoses were compared between HR and LR groups in each gender as well as total samples using Chi-square test with significance testing for Likelihood Ratio (see Table 2). P3 amplitudes from 12 electrodes (F3, FZ, F4, C3, CZ, C4, P3, PZ, P4, O1, OZ, O2) were analyzed using a repeated measures analysis of variance (RM-ANOVA) of the general linear model involving Risk Group (HR and LR), Age Group (12–15 and 16–25 years), and Gender (male and female) as between-subjects factors, and Task condition (Loss and Gain) and Region (frontal, central, parietal, and occipital) as within-subjects factors. Four scalp regions with three electrodes per region (Frontal: F3, FZ, F4; Central: C3, CZ, C4; Parietal: P3, PZ, P4; Occipital: O1, OZ, O2) were included in the model. Although affected status (i.e., individuals with any externalizing diagnosis as shown in Table 2) was initially used as a covariate in the RM-ANOVA model, it was removed from the later analysis which is presented here, as the covariate (i.e., externalizing
