The role of US signal value in contingency, drug conditioning, and learned helplessness.

In Pavlovian conditioning, organisms can learn that a conditioned stimulus (CS) signals the delivery of an unconditioned stimulus (US). The present paper first reviews research showing that organisms can also learn that a stimulus, normally considered to be a US, signals the delivery of another US. Second, the paper shows how such signal value may contribute to three conditioning phenomena that are of interest to many psychologists: contingency, drug conditioning, and learned helplessness. In addition to showing how such signal value may contribute to these three phenomena, suggestions for further research, as well as current gaps in the knowledge base, are outlined.