A conditioned response is a learned reaction to a previously neutral stimulus that has been paired with an unconditioned stimulus. It is the behavioral evidence that classical conditioning has taken place.

In Pavlov’s laboratory the conditioned response was salivation to the sound that predicted food. In everyday life it appears as the anxiety felt when approaching a place associated with past danger, the hunger triggered by the smell of a familiar restaurant, or the emotional warmth evoked by a song linked to a meaningful relationship. The conditioned response is often similar to the unconditioned response, yet it need not be identical; it can be a preparatory or compensatory reaction rather than a simple copy.

Once established, a conditioned response can be extinguished by presenting the conditioned stimulus without the unconditioned stimulus. Even after extinction, however, the response may reappear spontaneously or after a reminder of the original pairing, showing that the underlying association is not simply erased.

The conditioned response is the organism’s anticipatory adjustment to a world that contains reliable predictors.