Final answer:
Spontaneous recovery is the reappearance of an extinguished conditioned response after a rest period.
Step-by-step explanation:
The reappearance, after a time lapse, of an extinguished conditioned response (CR) is called spontaneous recovery. Spontaneous recovery refers to the temporary return of a previously extinguished conditioned response following a rest period. This phenomenon demonstrates that extinction does not completely erase a learned association and that the memory of the conditioned response can be reactivated under certain conditions.