UCS revaluation and conditioning models of acquired fears

Summary-Recent developments in the study of Pavlovian conditioning in humans have suggested that the strength of a conditioned response (CR) is affected not only by associative processes that link the conditioned stimulus (CS) with the unconditioned stimulus (UCS), but also by processes which lead the individual to revalue the UCS itself. These latter processes can frequently lead to dramatic changes in CR strength independently of any experience with the CS-UCS contingency. This paper discusses a number of ways in which UCS revaluation can be effected in human subjects, and discusses their implications for conditioning models of acquired fears. In the last 20 yr or so, our conception of the nature of conditioning in animals has changed considerably. No longer is Pavlovian conditioning considered to be the mechanistic learning of S-R reflexes, but it is seen to be comprised of a complex interaction of cognitive and information processing capacities. We know this primarily because of the inferential techniques that have been developed over this period which allow us to infer the nature of some of the unobservable processes that underlie Pavlovian conditioning in animals. Two of the most important findings involve the nature of the associations that underlie conditioning and the nature of the cognitive processes that mediate the conditioned response (CR). In particular, one technique, known as the postconditionin