The dependent variables that were most relevant to choice impulsivity were indifference points and k values. A mixed Experiment (1 or 2) × Sex × Alcohol Preference (High or Low) × Delay (0, 1, 2, 4, or 8) ANOVA was performed on indifference points. Main effects of Delay F(4.0,240.0) = 178.68, p < 0.001 and Alcohol Preference were detected F(1,60) = 14.04, p < 0.001, but no main effects of Experiment (p = 0.20), Sex (p = 0.58), or interactions with Alcohol Preference, Experiment, or Sex were observed (ps > 0.17). Mean indifference points and discounting curves are presented in Fig. 2; for clarity, we have included data from each of the 4 lines plotted separately, as well as the data collapsed across Alcohol Preference (bottom panel). These data indicated a consistent effect of a genetic difference in alcohol preference on indifference points in the DD task, consistent with impulsivity’s role in high alcohol consumption.
