What occurs during spontaneous recovery in classical conditioning?

During spontaneous recovery in classical conditioning, a conditioned response that has previously been extinguished unexpectedly reappears after a period of rest. This phenomenon demonstrates that even after conditioning has been weakened or eliminated through extinction—where the conditioned stimulus is presented without the unconditioned stimulus—there may still be a lingering association that can spontaneously resurface. The reemergence of the conditioned response suggests that the learning has not been completely erased but rather suppressed.

The other options point to different concepts in learning and conditioning. For instance, the notion of a conditioned stimulus being no longer paired with an unconditioned stimulus relates to the process of extinction itself rather than spontaneous recovery. Establishing a new conditioned response would indicate further learning rather than a reappearance of a prior response. Lastly, altering a reinforcement schedule pertains to operant conditioning, not classical conditioning, hence it does not apply in the context of spontaneous recovery.