Mean ± SEM preference (top) and difference (bottom) scores on the baseline (preconditioning, open bars) and test (post-conditioning, black bars) are shown for female rats that received Nonpaced Mating, Artificial Vaginocervical Stimulation (aVCS), Social Interaction or the Control treatment. n = 8–9 rats per group. Rats receiving either Nonpaced Mating or aVCS displayed a CPP for the compartment associated with the treatment: a significant increase in preference score coincident with a significant decrease in difference score, *p < 0.05 vs. Baseline.