classical conditioning
a type of learning in which an initially neutral stimulus—the conditioned stimulus (CS)—when paired with a stimulus that elicits a reflex response—the unconditioned stimulus (US)—results in a learned, or conditioned, response (CR) when the CS is presented. For example, the sound of a tone may be used as a CS, and food in a dog’s mouth as a US. After repeated pairings, namely, the tone followed immediately by food, the tone, which initially had no effect on salivation (i.e., was neutral with respect to it), will elicit salivation even if the food is not presented. Also called Pavlovian conditioning; respondent conditioning; Type I conditioning; Type S conditioning. [discovered in the early 20th century by Ivan Pavlov]