Classical conditioning is a type of learning that occurs through the association of stimuli and responses. It was first described by Russian psychologist Ivan Pavlov, who observed that dogs would begin to salivate when they heard a bell ringing, even if there was no food present. Pavlov discovered that the dogs had learned to associate the bell with food, and that the bell alone was enough to elicit the salivatory response. Classical conditioning is a type of learning that involves the formation of an association between a previously neutral stimulus and a naturally occurring stimulus. The neutral stimulus becomes able to elicit a response that was originally only produced by the naturally occurring stimulus. Classical conditioning has been studied extensively, and has been found to play a role in a wide range of psychological phenomena, including emotional responses, phobias, and addiction.