Another look at the extinction of conditioned flavor preferences: Amount of training and tests for spontaneous recovery.

A conditioned flavor preference develops when hungry or thirsty rats experience a neutral flavor mixed in solution with a nutrient. In two sets of studies, we previously demonstrated that this learned preference is highly sensitive to flavor nonreinforcement (i.e., exposure to the flavor without the nutrient) either prior to (latent inhibition), during (partial reinforcement), or following (extinction) flavor-nutrient pairings. In each of these studies we employed a nutrient devaluation procedure to assess the integrity of specific flavor-nutrient associations following extinction, but more recently Gonzalez, Morillas, and Hall (Journal of Experimental Psychology: Animal Learning & Cognition, 42, 380-390, 2016) observed that sensitivity to extinction in thirsty rats in this preparation may depend upon use of a post-conditioning nutrient devaluation procedure. To assess the generality of our earlier results, but without including a post-conditioning nutrient devaluation phase, we assessed in three experiments the role of the number of flavor-nutrient pairings given prior to extinction and the possibility of spontaneous recovery following a 3-week delay. We observed that extinction consistently weakened the flavor preference in thirsty rats (in spite of the absence of a nutrient devaluation procedure) and also found no evidence for spontaneous recovery. These results establish that our prior findings that conditioned flavor preferences are weakened by extinction are quite robust in thirsty rats and that these extinction effects may be fairly permanent.