Degraded contingency effect on running-based flavor aversion in rats: Testing the associative cue-competition account with flavors of minimal similarity

Wheel running endows aversion to a paired flavor in laboratory rats, reflecting a form of Pavlovian conditioning, where the contingency between the flavor and running is crucial for the development of flavor aversion. This study investigates the impact of additional wheel running (extra running) opportunities on the development of flavor aversion based on the contingent flavor-running training. All rats had access to a target solution, followed by the opportunity to run on 5 out of 10 training days. The three groups of rats differed in treatment on the remaining 5 days: Unsignaled rats ran after consuming familiar tap water, while signaled rats ran after ingesting a solution of another flavor (a cover cue), and control rats drank tap water without running. The post-training choice test revealed that the unsignaled rats exhibited a weaker aversion for the target flavor compared to the control rats, indicating an attenuating effect of the extra running on running-based conditioned flavor aversion. This "degraded contingency effect" remained unchanged when the running was signaled by another flavor cue: the target flavor preference of the signaled rats was equivalent to that of the unsignaled rats. The failure to obtain any effect of the second flavor on the target aversion suggests that the degraded contingency effect demonstrated here is better explained by either habituation or the comparator mechanism, rather than cue competition.