Conditioned Stimulus (CS): In classical conditioning, an originally irrelevant stimulus that, after association with an unconditioned stimulus (US), comes to trigger a conditioned response (CR).
Acquisition: In classical conditioning, the initial stage, when one links a neutral stimulus and an unconditioned stimulus so that the neutral stimulus begins triggering the conditioned response. In operant conditioning, the strengthening of a reinforced response.
Higher-order conditioning: A procedure in which the conditioning stimulus in the one conditioning experience is paired with a new neutral stimulus, creating a second (often weaker) conditioned stimulus
Extinction: The diminishing of a conditioned response; occurs when an unconditioned stimulus (US) does not follow a conditioned stimulus (CS); occurs in operant conditioning when a response is no longer reinforced.