Answer:Spontaneous recovery
Explanation:Spontaneous recovery is a phenomenon in which a behavior that was thought to have been extincted suddenly appears.
This response is the one that has resulted from classical and operant conditioning.
Spontaneous recovery in this way can be defined as a conditioned response that appears after it it rest period.
This usually occurs when the conditioned response stimulus is no longer associated with unconditioned stimulus.
Hans conditioned fear had extinguished after he left the military buy after months it came back again this is spontaneous recovery.