Pavlov, Ivan 1849-1936

PAVLOV’S LIFE

PAVLOV’S WORK

BIBLIOGRAPHY

Ivan Petrovich Pavlov, a Russian physiologist, received a Nobel Prize for his experimental studies of the interactions of gastrointestinal secretions with the activities of the pancreas and other glands. His observations on the role of the nervous system led him to explore what he called “psychic reflexes”—secretions of stomach acids elicited not by food itself but by stimuli such as the smells or tastes preceding food ingestion. He is best known for this discovery of conditioned, or conditional, reflexes and his subsequent experimental analyses of them. He created preparations using the salivary glands of dogs in which he could conveniently measure salivation elicited by metronomes or other arbitrary stimuli presented in various temporal relations to subsequent food deliveries.

Research inspired by Pavlov’s work has been extended to applications such as the modification of emotional responding through behavior therapies. Pavlov was a principled scientist and an outspoken critic of the Soviet system in Russia, and it is unfortunate that brainwashing and other coercive methods have sometimes been attributed to his influence. These attributions are inappropriate and inaccurate because such methods are neither procedurally nor historically derivative of Pavlov’s scientific contributions.

PAVLOV’S LIFE

Pavlov was the son of a parish priest. Some personal characteristics appeared early and remained with him throughout his life: a passion for physical work (especially in the garden), a love of books and learning, and an unshakable integrity. His experience in working with his hands stood him in good stead later in the speed, efficiency, and delicacy of his surgical skills. His readings led him to chemistry and biology, and he came to regard as two of his intellectual heroes the physiologist Ivan M. Sechenov (1829–1905), for construing conscious as well as unconscious activity as reflexes of the brain, and the naturalist Charles Darwin (1809–1882), for his theory of natural selection. Pavlov attended a religious seminary but in 1870 dropped theology in favor of physiology and then a medical degree in Saint Petersburg. In 1881 he married Seraphema (Sara) Vasilievna. They raised two sons, Vladimir and Vselvolod, and a daughter, Vera (a third son, Mirchik, died as a child). Sara was both devout and devoted to Pavlov, and he envied her religious faith.

After completing his dissertation, Pavlov studied in Germany and then began independent research on cardiac physiology in the Saint Petersburg laboratory of the physiologist Sergei P. Botkin (1832–1889), who soon entrusted the direction of his laboratory to Pavlov. This allowed Pavlov to devote all of his time to research. He involved himself thoroughly in all details of an experiment and even in his earliest experimental work regarded it as essential to work with the intact organism in order to maintain as far as possible the natural conditions of the physiological systems he chose to study. He had no patience with people with motives other than knowledge, such as those who saw research as a way to satisfy nonscientific agendas. The motto in Pavlov’s laboratory was “Observation and observation,” and he meant the direct observation of nature itself, not what someone had written about it.

Pavlov received his Nobel Prize in 1904. By the time of the Russian Revolution in 1917, his international reputation protected him from external intrusions on his research. Though he did not study the nervous system directly, he interpreted his findings in terms of changes in the irradiation of brain areas and attempted to extend his thinking to theories of language and of psychiatric disorders such as psychoses. In contrast to his contributions in physiology and conditioning, these theories did not fare well.

Pavlov maintained regular schedules of activity throughout his life, including outdoor exercise in the form of games and swims. Even during Joseph Stalin’s purges, he was outspoken in his denunciation of the Communist system, going so far as refusing admission to his laboratory to the Communist commissar of education and writing a letter of criticism to Stalin. Pavlov worked in his Saint Petersburg laboratory until shortly before his death of pneumonia in February 1936.

PAVLOV’S WORK

The term conditioned, from the Russian phrase for “conditioned reflexes,” might better have been translated as “conditional,” because the name was applied to reflexes conditional upon relations among stimuli. In respondent conditioning, one stimulus, the conditional stimulus (CS), signals the presentation of another, the unconditional stimulus (US). The responses respectively elicited by these stimuli are the conditional response (CR) and the unconditional response (UR). Pavlov’s conditioned salivary reflexes provide the prototypical example. When an originally neutral bell repeatedly signals food in the mouth of a hungry dog, it becomes a CS as salivation begins to be elicited by this signaling stimulus as well as by the US, the food itself.

Ironically, Pavlov may never have used a bell in his experiments; his rare mention of bells occurs only in later work, where it probably refers to electrically operated devices. The ubiquitous references to Pavlov’s bell probably originated with a common example of a conditioned reflex in popular writings about Pavlov’s research: a dinner bell eliciting salivation in those called to the table (Pavlov’s own bell was kept on his desk, presumably for summoning servants).

Pavlov’s conditioning procedure has been called “respondent,” “Pavlovian,” and “classical conditioning,” distinguishing it from procedures studied especially by the American psychologists Edward L. Thorndike (1874–1949) and later B. F. Skinner (1904–1990). In Pavlov’s procedure the important features are the relations between two stimuli, whereas in Thorndike’s and Skinner’s instrumental or operant procedures they are the relations between a stimulus and the response that has produced it.

Pavlov arranged various temporal relations between the CS and the US. For example, in both trace and delay conditioning, a relatively long time elapsed between CS and US; they were distinguished by whether the CS turned off or remained present in the interim. In both types conditional responding began shortly after the start of the CS, but with successive trials it gradually moved closer to the time of the US. Trace conditioning acquired its name from Pavlov’s assumption that the CS had to leave some trace in the nervous system to be effective.

Attention to Pavlovian conditioning followed from how easily it could be related to the concept of association, a learning principle with substantial precedent in philosophy and psychology. Learning was said to take place through associations of ideas, and conditional reflexes seemed to represent a primitive example of their formation. In a kind of mental chemistry, ideas were thought to be associated through such properties as having common elements or occurring together in time. Thus conditioning was regarded as at the root of all learning.

During Pavlov’s lifetime, conditioning was seen as a sort of stimulus substitution in which, through CS-US pairing, the CS acquires power to elicit the UR. But it is now clear that this account misrepresents what happens in at least three ways. First, conditioning depends not on CS-US pairings but rather on whether the CS predicts the US. If the CS is as often followed by no US as by the US, the two are often paired, but conditioning does not occur because the CS does not predict a US delivery. Second, in many preparations the CR differs in form or other properties from the UR. For example, with an intravenous opiate as the US, the CR is a diminished pain threshold, whereas the UR is a heightened pain threshold; the CS does not substitute for the US (similarly, if a metronome becomes a CS, the dog does not try to eat it). Third, preparations in which the typical latency between US and UR is long enough that a CS can be presented after the US but either before or after the UR show that conditioning depends on the CS-UR rather than the CS-US sequence. Conditioning occurs as long as the CS precedes the UR, so the relation of the CS to responding is more important than its relation to stimuli.

SEE ALSO Classical Conditioning; Empiricism; Operant Conditioning; Psychology; Skinner, B. F.; Thorndike, Edward; Union of Soviet Socialist Republics

BIBLIOGRAPHY

Babkin, Boris P. 1949. Pavlov: A Biography. Chicago: University of Chicago Press.

Catania, A. Charles, and Victor G. Laties. 1999. Pavlov and Skinner: Two Lives in Science. Russian Journal of Physiology 85 (Pavlov Sesquicentennial Issue): 1307–1313.

Donahoe, John W., and Rocio Vegas. 2004. Pavlovian Conditioning: The CS-UR Relation. Journal of Experimental Psychology: Animal Behavior Processes 30: 17–33.

Pavlov, Ivan P. 1927. Conditioned Reflexes. Trans. G. V. Anrep. London: Oxford University Press.

Rescorla, Robert A. 1988. Pavlovian Conditioning: It’s Not What You Think It Is. American Psychologist 43: 151–160.

Siegel, Shepard, Riley E. Hinson, Marvin D. Krank, and Jane McCully. 1982. Heroin “Overdose” Death: The Contribution of Drug-Associated Environmental Cues. Science 216: 436–437.

A. Charles Catania

Pavlov, Ivan Ivan Petrovich Pavlov (1849–1936) was a Russian physiologist who won the Nobel Prize in Physiology or Medicine in 1904 for his work on the physiology of gastric secretion. However he is more famous for his subsequent studies on reflexes and for laying the foundations of the field of behavioural psychology.

He was the eldest of eleven children of a Russian orthodox priest, and entered the theological seminary in his home town of Ryazan, in provincial Russia, with the intention of following his father's profession. In later years he recalled to colleagues that it was seeing an illustration of the gastrointestinal tract in a book by the English writer George Henry Lewes, The Physiology of Common Life, that persuaded him to leave the religious life to study the natural sciences. This drawing of the alimentary system was based on the physiological research work of Claude Bernard, and the complexity of it challenged Pavlov to explore its intricacies further.

Pavlov entered the university of St Petersburg in 1879 to study medicine, and, after graduating, obtained his doctorate in 1883 from the Medical Military Academy, also in St Petersburg. As a student he had been particularly influenced by, and collaborated with, the physiologist Elie Cyon, and on Cyon's advice he studied the nerves to the pancreas, and identified those which stimulated the secretion of its digestive juices; for this he was awarded the University's gold medal. It was thus a natural progression for him to travel abroad to study with two of the greatest living physiologists, Carl Ludwig in Leipzig and Rudolph Heidenhain in Breslau. Soon after returning to St Petersburg he was appointed Professor of Physiology at the Medical Military Academy, in 1890. He remained there until 1924, when the newly-created Soviet Academy of Sciences established a special Institute of Physiology for him.

Pavlov's work can be divided into two distinct phases: earlier work on digestion, and later work on the conditioned reflex. He was a noted experimenter and renowned surgeon, and, using anaesthetized experimental animals, usually dogs, he created several ‘windows’ in the body through which the secretions of the stomach, salivary glands, pancreas, and intestine could be collected. Of particular value was his ability to bring the stomach out through the body wall with its nerve and blood supply intact, so that he could observe its functions in a conscious dog, behaving normally. He also made an artificial hole in the oesophagus (gullet) so that food taken into the mouth escaped before it reached the stomach. Together, these allowed him to show that gastric juices were secreted in anticipation of receiving food from the mouth, and also to collect and study the secretions uncontaminated by food particles. His techniques led to the discovery and identification of several key enzymes and mechanisms that occur in normal digestion. This work had commercial spin-offs: from 1898 onwards Pavlov's lab contained a ‘gastric acid factory’, the acid produced by the dogs being collected and sold as a remedy for dyspepsia, and by 1904 the project was contributing over 65% of the laboratory's budget.

Perhaps the most influential observation he made was in the early years of the twentieth century, when he noticed that even the mere sight and smell of food could stimulate the anticipatory production of salivary and gastric secretions in his experimental dogs. Further systematic experiments on this phenomenon revealed that if the appearance of food was repeatedly preceded by the ringing of a bell, then eventually the dog would produce secretions after hearing the bell, and before or without the appearance of food. This encouraged Pavlov and his co-workers to turn their attention to the activities of the higher nervous system and to the further study of such responses, which he originally called a ‘conditional reflex’, because ‘their inclusion as reflexes had for him a conditional character’. To English speakers the expression has now become known as ‘conditioned reflex’, although the French still refer to ‘le réflexe conditionnel’. His work from then onwards focused on links between nervous activity and behaviour, extending into observational and theoretical work on human behaviour. Many of his views were rapidly absorbed into psychological and psychiatric practice and teaching.

By the time of the Russian and Bolshevik revolutions in 1917, Pavlov was a world-renowned scientist. He was subsequently courted by the new regime, which wanted to build up Soviet science. In the years immediately after the revolutions Pavlov frequently denounced the Bolsheviks and their ideology, and at one period considered emigrating. He was, however, offered privileges for himself and his colleagues that permitted him to continue working, and by the 1930s had apparently reconciled himself to living in Soviet Russia, particularly through his friendship with Nikolai Bukharin. He continued nonetheless to be a critic of the government, and was subject to secret police surveillance for many years up to his death in 1936.

E. M. Tansey

Bibliography

Brown, E. M. (1990). Ivan Petrovich Pavlov . In Nobel Laureates in Medicine or Physiology: a biographical dictionary, (ed. D. M. Fox, M. Meldrum, and I. Rezak). Garland Publishing, New York.
Todes, D. P. (1995). Pavlov and the Bolsheviks. History and Philosophy of the Life Sciences, 17, 379–418.
Todes, D. P. (1997). Pavlov's physiology factory. Isis, 88, 205–46.
Todes, D. P. (1997). From the machine to the ghost within: Pavlov's transition from digestive physiology to conditional reflexes. American Psychologist, 52, 947–55.

Ivan Pavlov

1849-1936
Russian physiologist and Nobel laureate best known for his development of the concept of the conditioned reflex, or conditioned response.

Ivan Pavlov was born into an impoverished family in the rural village of Ryazan, Russia. He won a government scholarship to the University of St. Petersburg and studied medicine at the Imperial Medical Academy, receiving his degree in 1883. In 1890, Pavlov was appointed to a professorship at the St. Petersburg Military Academy and a few years later joined the faculty of the University of St. Petersburg. He organized the Institute of Experimental Medicine in 1895, which was to be his research laboratory for the next 40 years.

In the 1890s, Pavlov investigated the workings of the digestive system—focusing on digestive secretions— using special surgically created openings in the digestive tracts of dogs, a project strongly influenced by the work of an earlier physiologist, Ivan Sechenov (1829-1905). As a result of this research, Pavlov was awarded the Nobel Prize for Physiology and Medicine in 1904. During his investigations in this area, Pavlov observed that normal, healthy dogs would salivate upon seeing their keeper, apparently in anticipation of being fed. This led him, through a systematic series of experiments, to formulate the principles of the conditioned response , which he believed could be applied to humans as well as to animals. According to Pavlov's system, an unconditioned stimulus, such as offering food to a dog, produced a response, or unconditioned reflex, that required no training (salivation). In contrast, a normally neutral act, such as ringing a bell, became a conditioned stimulus when associated with the offering of food and eventually would produce salivation also, but as a conditioned reflex. According to Pavlov, the conditioned reflex was a physiological phenomenon caused by the creation of new reflexive pathways created in the cortex of the brain by the conditioning process. In further studies of the cortex, Pavlov posited the presence of two important processes that accompany conditioning: excitation, which leads to the acquisition of conditioned responses, and inhibition, which suppresses them. He eventually came to believe that cortical inhibition was an important factor in the sleep process.

Pavlov continued working with conditioned reflexes throughout the early decades of the twentieth century, generating several addition principles through further experimentation. The principle of timing dictated that the neutral stimulus must precede the unconditioned reflex in order to become a conditioned stimulus. (In other words, a buzzer would have to go off before food was offered to a dog in order for the dog to associate the food and buzzer with each other). The concept of extinction referred to the fact that a conditioned response could be "unlearned" if the neutral stimulus (buzzer) was repeatedly used without reinforcement (food). Generalization was the name given to the observation that a stimulus similar to the conditioned stimulus would still produce a response as the dog generalized from its original experience to a similar one, but the response would be less pronounced in proportion to the difference between the stimuli. Finally, testing the limits of the dogs' ability to differentiate among stimuli led, unexpectedly, to experimental

neuroses, similar to mental breakdowns in humans, when the subjects were forced to confront conflicting or ambiguous stimuli for any length of time. Observing the ways in which neurotic symptoms differed among test subjects led Pavlov between 1916 and 1936 to formulate a theory of four different types of temperament linked to physiological differences based on differences in excitatory and inhibitory activity. Attempting to extend the implications of this theory to human psychopathology, Pavlov helped establish the Soviet Union's continuing tradition of organically-based psychiatric treatment.

Pavlov, who died of pneumonia in 1936, tried to apply his ideas to psychiatry, and was influential enough to be considered one of the founders of Russian psychiatry, and he remains a dominant figure in Russian psychology. Although he never considered himself a psychologist, Pavlov's ultimate belief in conditioning as the fundamental unit of learning in humans and animals provided one of the cornerstones of the behaviorist school of psychology in the United States. It is ironic that, although Pavlov was a staunch critic of communism, in the late 1920s Joseph Stalin (1879-1953) chose Pavlov's work as the basis for a new Soviet psychology. Pavlov's books include Lectures on the Work of the Principal Digestive Glands (1897), Lectures on Conditioned Reflexes (1928), and Conditioned Reflexes and Psychiatry (1941).

See also Behaviorism

Further Reading

Babkin, Boris P. Pavlov: A Biography. Chicago: University of Chicago Press, 1949.