Respondent (classical) conditioning is based on innate stimulus-response relationships called reflexes. In his famous experiments with dogs, Pavlov usually used the salivary reflex, namely salivation (unconditioned response) following the taste of food (unconditioned stimulus). Pairing a neutral stimulus, for example a bell (conditioned stimulus) with food caused the bell to elicit salivation (conditioned response). Thus, in classical conditioning, the conditioned stimulus becomes a signal for a biologically significant consequence. Note that in respondent conditioning, unlike operant conditioning, the response does not "produce" a reinforcer or punisher (e.g. the dog does not get food "because" it salivates).