extinction

Meaning: In classical conditioning, a conditioned stimulus (a bell) that was paired with an unconditioned stimulus (food) triggers a conditioned response (salivation). If the bell is presented repeatedly without food, the response declines. In operant conditioning, extinction occurs when a previously reinforced behavior stops producing the reinforcer, and the behavior becomes less frequent. Early in operant extinction there is often a brief rise in the behavior, called an extinction burst. After a rest period, the conditioned response often returns in weaker form. This is spontaneous recovery, and it suggests the original association is still present.

On the MCAT: Passages usually give a graph of response strength across trials: a rise during acquisition, a fall during extinction, a gap, then a partial rebound. You may be asked which stimulus or reinforcer was withheld, or to name the rebound. A common comparison is resistance to extinction. Behavior learned under partial (intermittent) reinforcement, especially variable-ratio schedules, is more resistant to extinction than behavior learned under continuous reinforcement.

Common confusion: Extinction is not punishment and not forgetting. Punishment decreases behavior by adding an aversive stimulus or removing a pleasant one, while extinction withholds the reinforcer or the pairing. Extinction is also not unlearning. Spontaneous recovery, and the fast relearning that often follows, show that the original learning is suppressed rather than erased.