Mean number of infusion attempts made by rats in all three SD conditions (SD0, SD4, and SD8) during the 45 min extinction period before (open bars) and after (closed bars) the passive infusion of cocaine. Rats with a history of low drug-taking (SD0: n=7, SD4: n=6, and SD8: n=7) can be viewed in the left panel, while rats with a history of high drug-taking (SD0: n=7, SD4: n=8, and SD8: n=7) can be viewed in the right panel. * denotes statistical significance (p < 0.05).