Redefining Pavlovian conditioning.

Pavlovian conditioning is typically defined as a form of learning in which a neutral stimulus, through repeated pairing with an unconditional stimulus (US) that elicits an unconditional response (UR), comes to evoke a conditional response (CR) that is related to the UR. I argue that each substantive element of this common definition is empirically and conceptually flawed and that it obscures conditioning's central role in everyday adaptive behavior. I develop an alternative framework in which Pavlovian conditioning is the process by which organisms learn to recognize biologically significant objects (e.g., foods, mates, predators, toxins) and generate phylogenetically appropriate responses via functional behavior systems organized along imminence continua. Within this view, CSs and USs are features of objects, with the difference that a US serves to tag the object as belonging to a specific behavior system. CRs consist of behavior system mode-specific behaviors and broad changes in reactivity (Pavlovian sensitization). This reconceptualization provides new definitions of CS, US, CR, and UR and situates Pavlovian conditioning as a pervasive mechanism for immediate adaptive action rather than a narrow laboratory phenomenon.