Mean reinforcers obtained (±SEM) during the first session of Experiment 4 conducted with male and female rats given saline (0.00 mg/kg, Sal), 0.015 mg/kg, IV nicotine (Nic), or 0.03 mg/kg, IV Nic on a FR1 schedule of reinforcement while allowed limited social contact through a mesh barrier (Soc: solid bars) or while isolated (Iso: open bars). Inset illustrates the social condition by dose interaction. N/condition ranged from 10-14. Asterisk (*) represents a difference from Iso, test of simple effects, p <0.05.