Spontaneous recovery is the reappearance of a conditioned response after a rest period following extinction. The response returns even though no further pairing of the conditioned and unconditioned stimuli has occurred.

After a conditioned response has been extinguished by repeated presentation of the conditioned stimulus alone, a pause is introduced. When the conditioned stimulus is presented again, the response often reappears at reduced strength. Additional extinction trials weaken it once more, yet spontaneous recovery can occur again after further rests. The phenomenon shows that extinction does not erase the original learning; it creates a competing inhibitory association that can temporarily dissipate.

Spontaneous recovery is observed in both classical and operant conditioning. It helps explain why extinguished fears or habits sometimes return after a period of calm. Complete elimination of a conditioned response may require multiple extinction sessions spaced over time or extinction conducted in varied contexts.

A response that seemed gone can reappear after a pause. That return is spontaneous recovery.