Unconditioned Stimulus (US):The unconditioned stimulus is a stimulus that automatically triggers an unlearned response. For example, in Pavlov's experiment, the food was the unconditioned stimulus.
Conditioned Stimulus (CS):The conditioned stimulus is a previously neutral stimulus that, after being paired with an unconditioned stimulus, elicits a learned response. In Pavlov's experiment, the bell became the conditioned stimulus after it was repeatedly paired with food.
Conditioned Response (CR):The conditioned response is the learned response that occurs when an organism reacts to a conditioned stimulus. In Pavlov's experiment, salivating at the sound of the bell became the conditioned response.