What is classical conditioning?
Classical conditioning is learning an association between two stimuli. While studying digestion, Ivan Pavlov noticed that dogs began to salivate before food arrived, for example at the sound of an assistant's footsteps. He then repeatedly paired a sound such as a metronome with food, and found that the sound alone came to produce salivation. Pavlov received the 1904 Nobel Prize in Physiology or Medicine for his work on digestion, and his research on conditioned reflexes became a foundation of behaviorism.
Four key terms
- Unconditioned stimulus (US)
- Triggers a response without learning (food)
- Unconditioned response (UR)
- The natural response to the US (salivation)
- Conditioned stimulus (CS)
- A once-neutral stimulus that now triggers a response (the sound)
- Conditioned response (CR)
- The learned response to the CS alone
Key phenomena
- Acquisition: the association forms best when the CS comes shortly before the US.
- Extinction: presenting the CS repeatedly without the US weakens the conditioned response.
- Spontaneous recovery: after a rest, an extinguished response can briefly return.
- Generalization: stimuli similar to the CS also produce the response.
- Discrimination: the learner responds to the paired stimulus but not to others.
Everyday examples and uses
A song that brings back the feelings of a past summer, or an advertisement that keeps pairing a product with a well-liked celebrity, rely on the same principle. Systematic desensitization and exposure therapy for phobias work by extinguishing conditioned fear. Watson and Rayner's 1920 "Little Albert" study claimed that fear could be conditioned in an infant, but it is now regarded as seriously unethical.
How it differs from operant conditioning
Classical conditioning pairs stimuli and changes automatic, reflexive responses. Operant conditioning changes how often a voluntary behavior occurs through its consequences, reinforcement and punishment. In classical conditioning the stimuli arrive regardless of what the learner does; in operant conditioning the outcome depends on the learner's behavior.
References
- Pavlov, I. P. (1927). Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex (G. V. Anrep, Trans.). London: Oxford University Press.
- Watson, J. B., & Rayner, R. (1920). Conditioned emotional reactions. Journal of Experimental Psychology, 3(1), 1–14.
- Rescorla, R. A. (1988). Pavlovian conditioning: It's not what you think it is. American Psychologist, 43(3), 151–160.
- The Nobel Prize in Physiology or Medicine 1904: Ivan Pavlov. NobelPrize.org.