Second-order conditioning during a compound extinction treatment

Two conditioned taste aversion experiments with rats were conducted to establish if a target taste that had received a prior pairing with illness could be subject to second-order conditioning during extinction treatment in compound with a flavor that also received prior conditioning. In these experiments, the occurrence of second-order conditioning was indicated by protection from extinction of the aversion elicited by the target taste. This possibility, although intuitive, deserves attention because current associative models [e.g., Rescorla, R. A., & Wagner, A. R. (1972). A theory of Pavlovian conditioning: variations in the effectiveness of reinforcement and nonreinforcement. In A. H. Black & W. F. Prokasy (Eds.), Classical conditioning II: Current research and theory (pp. 64–99). New York: Appleton-Century-Crofts.] predict exactly the opposite outcome, namely, that compound extinction of two CSs should result in enhanced extinction.