Pavlov, Ivan P.

Ivan Petrovich Pavlov (1849–1936) was a Russian physiologist who developed one of the two basic procedures used to study behavioral change in the laboratory. His procedure is variously called Pavlovian, classical, or respondent conditioning. In the Pavlovian procedure, the learner is presented with a “neutral” stimulus, followed closely in time by a stimulus that already elicits behavior. In Pavlov's laboratory, the neutral stimulus was commonly the ticking sound of a metronome, and the eliciting stimulus was food that elicited salivation. After a number of pairings of the ticking sound with food, the sound alone could evoke [Page 428]salivation. Thus, the procedure produced a new relation between the environment and behavior: the sound-salivation relation. The second procedure used to study behavioral change is called operant or instrumental conditioning and was independently developed by Edward L. Thorndike at about the same time, around 1900. In contrast to Pavlov's procedure, in the operant procedure, a behavior instead of a stimulus precedes the eliciting stimulus. Outside the laboratory, elicitors are typically preceded by both stimuli and behavior, as when seeing and then eating ice cream are followed by stimulation of receptors in the mouth and elicitation of salivation. As a result, the sight of ice cream comes to control both salivating and eating.

Pavlov began to study behavioral change after incidental observations during his studies of digestion. Using his skills as a surgeon—he was ambidextrous—Pavlov had been able to expose nerves controlling the heart, and ducts secreting digestive juices during food intake. For this work, he would receive a Nobel Prize for medicine in 1904. However, a few years before receiving the prize, Pavlov noticed that the salivary glands would often begin to secrete before food was introduced into the mouth. For example, salivation might be evoked by the sound of the footsteps of the caretaker who normally fed the dogs or by the mere sight of food. Instead of regarding these events as unwanted intrusions into his study of digestion, Pavlov realized that he had inadvertently identified a method to study learning in the laboratory. Accordingly, he dropped his study of the neural control of digestion and—against the advice of colleagues—turned his attention to what he called “psychic reflexes.” In 1903, his first paper on conditioning was presented to the 14th Medical Congress in Madrid, in which he described the basic phenomena using terminology that is now standard in the field. Among the phenomena were extinction, discrimination, generalization, spontaneous recovery, and higher-order conditioning. Higher-order conditioning demonstrated that new environment-behavior relations could be selected not only by innate eliciting stimuli (e.g., food-elicited salivation) but also by learned elicitors (e.g., a light that was paired with only the sound of a metronome would come to evoke salivation if the sound had previously been paired with food). Thus, the range of possible elicitors that served as reinforcers could expand with experience.

After the Communist Revolution in Russia, the Soviet government continued to support Pavlov as one of their most famous scientists. However, Pavlov resisted the intrusion of politics into science. When his status entitled him to special food rations, he refused unless members of his institute also received them. When admission to the university was about to be denied to an applicant because he was the son of a priest, Pavlov responded that he also was the son of a priest. When political figures were proposed for membership in scientific societies, Pavlov alone opposed them. Pavlov remained scientifically productive throughout his long life, devoting his later years to the application of conditioning for the alleviation of mental illness.

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