Final answer:
A temporary increase in the rate of responding after a period of extinction is known as spontaneous recovery, where the extinguished conditioned response reappears for a brief time.
Step-by-step explanation:
After a period of extinction, a temporary increase in the rate of responding is called spontaneous recovery. This phenomenon occurs when the conditioned response returns after it had been extinguished. For example, Pavlov's dogs, after a break from conditioning, once again began to salivate at hearing the bell even though the bell had stopped being paired with food. This response is temporary and generally weaker than the original conditioned response, demonstrating how learned behaviors can resurface even after they seem to have been unlearned.
It is not to be confused with stimulus discrimination, where an organism learns to respond differently to similar but not identical stimuli, or stimulus generalization, where an organism responds to stimuli that are similar to the conditioned stimulus. Moreover, spontaneous recovery differs from shaping, which involves rewarding successive approximations toward a target behavior.