Fig. 8. Effects of drug-free (abstinence) periods on anticipation and consumption of cocaine under the FI-FR response chain.

A) Incubation-like increases in fixed-interval responding for cocaine (solid bars; left y-axis), but not saccharin (striped bars; right-y axis) reinforcement. B) Renewed access to cocaine after a 15-day drug-free period resulted in increased FI responding (solid bar) and decreased cocaine intake (open bar). All values depicted as a mean (±SEM). *p<.05, ,**p < .01,***p < 0.001.