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. Author manuscript; available in PMC: 2010 Mar 15.
Published in final edited form as: Psychopharmacology (Berl). 2006 Jul 18;190(3):353–362. doi: 10.1007/s00213-006-0454-8

Fig. 3.

Fig. 3

Mean (+SEM) number of infusions earned when responding is reinforced with NIC or SAL in the absence of a contingent VS on an escalating fixed ratio schedule (a) or a progressive ratio schedule (b, SAL + no VS group is replicated in each panel). The schedule of reinforcement is indicated below the abscissa. Significant between-groups comparisons at each day are indicated as follows: *p<0.05, all comparisons (0.09 mg/kg per infusion > saline, 0.01 and 0.03 mg/kg per infusion)