50 Pavlov & Classical Conditioning

Based on Research by Ivan Pavlov, M.D.. Psychology Science Minute written by Kyle Piecora, M.S.

A key figure in the psychology world is Dr. Ivan Pavlov, whose vital discovery of classical conditioning has changed the way psychologists look at learning.  Pavlov was studying digestion and the nervous system, measuring the amount of salivation in response to food quantities.

He labeled the food an unconditioned (or unlearned) stimulus that set off an automatic, unlearned or unconditioned response in the dog’s mouth: salivation.  However, he found that when he entered the room, the dogs would salivate before the food was presented.  He was irritated that this kind of salivations was interfering with his experiment.

He hypothesized that if another stimulus, such as a ringing bell, occurred just before the food, the bell alone may eventually trigger the dogs’ salivation, because the bell occurring just prior to the food presentation predicted the food.

Sure enough, the more frequently Pavlov presented the bell just before the food, the more saliva flowed, something that would not have had this effect on his dogs prior to his study!  Thus the dogs had learned this association.  When in 1901 Pavlov realized that he had made an important scientific discovery, he devoted the rest of his life to studying what is now called Classical Conditioning.


Pavlov, Ivan. (1927). Conditioned Reflexes. Oxford, England:  Clarendon Press.

Pavlov, I. P. (1928). Lectures On Conditioned Reflexes. (Translated by W.H. Gantt) London: Allen and Unwin.

Pavlov, I. P. (1927). Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex. Translated and Edited by G. V. Anrep. London: Oxford University Press.

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