The results of the study should be viewed with caution because of a few limitations. Six subjects in the HR group and 3 subjects in the LR group had marijuana dependence, and one from each group had cocaine dependence. However, visual analysis of the wave pattern of these subjects did not show any gross deviation from others in the same group. Analysis of the data without including these subjects still yielded similar results. In addition, it has been shown that the presence of comorbid marijuana and cocaine dependence did not have any effect on N4 of the alcoholic subjects in a similar semantic priming task (Ceballos et al., 2005). On the other hand, subjects in both groups were not matched on any measure of intelligence. However, this might not be a major limitation considering the reaction time and latency measures did not differ between the two groups. Another, important factor to consider is that the high risk subjects, despite having a parent who is alcohol dependent, were not alcohol dependent themselves, though they may have the genetic risk to develop
