Timeline of experimental procedures across PNDs in Experiments 1-3 (a) and mean reinforcers obtained (±SEM) across acquisition sessions in (b) Experiment 1 with male rats given access to 0.015 mg/kg, IV nicotine, (c) Experiment 2 with female rats given access to 0.015 mg/kg, IV nicotine, and (d) Experiment 3 with male rats given access to saline (i.e., 0.00 mg/kg, IV). Sessions were conducted on a FR1 schedule of reinforcement while rats were isolated (Iso: open squares) or while allowed limited social contact through a mesh barrier (Soc: closed circles). See Table 1 for n/condition. Asterisk (*) represents a difference from Iso, test of simple effects, p <0.05.