Differential perseveration of reinstatement by stimuli conditioned to cocaine (COC) vs. natural reward (SCM). (A) Session lengths constant across experimental phases for the respective reinforcer (COC = 60 min; SCM 20 min). (B) Reinstatement session lengths modified to be constant across reinforcers (COC = 30 min; SCM 30 min). (C) Effects of SCM stimulus information (“compound” SD consisting of the auditory S+ plus the SCM olfactory cue) on reinstatement. Self-administration (left panels A – C): Mean (±SEM) responses averaged across the final three self-administration/conditioning sessions. Responding was differentially reinforced in the presence of discriminative (i.e., occasion setting contextual) stimuli signaling the availability (S+) or nonavailability (S−) of COC or SCM. ***p < 0.001 vs. non-reward and S− conditions. Extinction (center panels A – C): Mean (±SEM) non-reinforced responses averaged across the final three extinction sessions. Reinstatement (right panels A – C): Effects of the non-reward S− tested one day after the final extinction session, followed by effects of the reward-predictive S+ across four reinstatement sessions. ***p < 0.001, **p < 0.01, *p < 0.05, vs. corresponding EXT and S− tests; +++p < 0.001, ++p < 0.01, vs. SCM S+.