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Acquisition of cocaine self-administration behavior in sign-trackers (n=14) and goal-trackers (n=16). (a) The mean ± SEM number of cocaine infusions per minute for infusion criteria 5, 10, 15, and 25 (0.5 mg/kg/inf) and 40 and 80 (0.2 mg/kg/inf). (b) The mean ± SEM number of active and inactive nose poke responses at each infusion criterion.
