Fig. 4.

Subjects that had a significant place preference in Fig. 3 were extinguished and then the response probed with a priming dose of 5 mg/kg cocaine to determine the level of reinstatement. A preference score (calculated as the time on [drug side − time on saline side])/[drug + saline)]) of less than 0.54 was used as the criterion for extinction; anything above a score of 0.54 is considered a preference.