Consistent with past findings (Hill et al., 1999), visual P300 amplitude decreased significantly with age from 17 to 24 years in young men from a community sample. This finding is consistent with the results of studies using the same task as used here (Hill et al., 1999; Katsanis et al., 1996), as well as with a variety of other visual tasks (Courchesne, 1978; Friedman et al., 1989; Johnson, 1989; Mullis, Holcomb, Diner, & Dykman, 1985; Taylor, 1993). As we had predicted, developmental trajectories differed significantly across groups of young men varying in paternal history of externalizing problems. On the basis of findings of Hill and colleagues (Hill & Shen, 2002; Hill et al., 1999), we had predicted that sons with heightened risk would have developmental trajectories characterized by lower intercepts and less change with age relative to those at low risk. Consistent with P300 amplitude being associated with risk for an externalizing dimension underlying vulnerability for substance use disorders (Hicks et al., 2007; Patrick et al., 2006) and findings that paternal AAB is a more severe indicator of externalizing than
