International Journal of Comparative Psychology

Wheel running establishes conditioned aversion in rats to a taste solution consumed shortly prior to the running. Many studies have shown that this is a case of Pavlovian conditioning, in which the taste and running respectively act as the conditioned stimulus (CS) and the unconditioned stimulus (US), but extinction of this running-based taste aversion has not been explicitly demonstrated. Experiment 1, using a within-subjects design, showed that saccharin aversion formerly established by a single pairing of an exposure to saccharin solution with a running opportunity was extinguished by two daily exposures to the saccharin solution. However, there was no spontaneous recovery from extinction in the tests which were administered 6 and 27 days after the extinction days. Experiment 2, using a between-groups design, successfully demonstrated extinction and spontaneous recovery of running-based saccharin aversion, when rats were treated with a paradigm of 8 conditioning days, 8 extinction days, and 8 retention days.