Spontaneous recovery

Spontaneous recovery is a phenomenon of learning and memory that was first named and described by Pavlov in his studies of classical (Pavlovian) conditioning. In that context, it refers to the re-emergence of a previously extinguished conditioned response after a delay. Such a recovery of "lost" behaviors can be observed within a variety of domains, and the recovery of lost human memories is often of particular interest. This article summarizes research in a number of related areas.

Spontaneous recovery is associated with the learning process called classical conditioning, in which an organism learns to associate a neutral stimulus with a stimulus which produces an unconditioned response, such that the previously neutral stimulus comes to produce its own response, which is usually similar to that produced by the unconditioned stimulus. Although aspects of classical conditioning had been noted by previous scholars, the first experimental analysis of the process was done by Ivan Pavlov, a nineteenth-century physiologist came across the associative effects of conditioning while conducting research on canine digestion.

To study digestion, Pavlov presented various types of food to dogs and measured their salivary response. Pavlov noticed that with repeated testing, the dogs began to salivate before the food was presented, for example when they heard the footsteps of an approaching experimenter. Pavlov named this anticipatory behavior the "conditioned" response or, more exactly, the "conditional" response. He and his associates discovered and published the basic facts about this process, which has come to be called classical or Pavlovian conditioning.

Among the phenomena that Pavlov observed was the partial recovery of a classically conditioned response after it had been extinguished by withholding the unconditioned stimulus. This recovery happened in the absence of any further unconditioned stimulation. Pavlov referred to this phenomenon as spontaneous recovery. Although spontaneous recovery increases with time following the extinction procedure, such conditioned responses do not generally return to full strength. Moreover, with repeated recovery/extinction cycles, the conditioned response tends to be less intense with each period of recovery. On the other hand, reconditioning by pairing the same conditioned and unconditioned stimuli usually occurs much faster than the original conditioning.

A key conclusion is that extinction leaves a permanent trace; it does not simply reverse conditioning. This conclusion has been very important to both theories of classical conditioning and to its applications in behavioral therapy, See the main article on classical conditioning for the origins of conditioning and a discussion of spontaneous recovery in the context of related phenomena within classical conditioning.

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