Final answer:
The reappearance of a learned response after it has been extinguished is called spontaneous recovery. This effect, demonstrated in Pavlov's classical conditioning experiments, indicates that a suppressed conditioned response can resurface after a rest period.
Step-by-step explanation:
The reappearance of a learned response after extinction has occurred is called spontaneous recovery. This phenomenon is observed when, after a period of extinction where the conditioned stimulus is presented without the unconditioned stimulus, the conditioned response reappears, once the conditioned stimulus is presented again following a rest period. Pavlov's classical conditioning experiments with dogs demonstrated this when the dogs began to salivate to the sound of a bell, a previously extinguished response, after a period of time without hearing the bell associated with food.
Extinction itself occurs when the conditioned stimulus is repeatedly presented without the unconditioned stimulus, leading to a decrease in the conditioned response. However, spontaneous recovery shows that the learned association is not completely erased but merely suppressed, able to resurface under the right circumstances. This shows the resilience of the learned associations in the brain.