Associative relations in instrumental learning: The eighteenth Bartlett memorial lecture

Instrumental learning involves three primary events: a stimulus (S), a response (R), and an outcome (O). Evidence is reviewed indicating the presence of binary associations among those events, as well as a hierarchical structure of the form S-(R-O). Experiments examining the conditions that produce learning, the content of the learning once it has occurred, and the way learning maps into performance all suggest the presence of such a hierarchical structure.