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Acquisition of self-administration behavior in sign trackers (n=12) and goal trackers (n=15). (a) The mean+SEM number of cocaine infusions per minute for infusion criteria 10, 20, 40, and 80 (0.2 mg/kg/inf). (b) The mean+SEM number of active (circles) and inactive (squares) nose-poke responses at each infusion criterion. (c) The mean+SEM cumulative interinfusion interval (III) during the final two self-administration sessions at IC 80.
