Ivan Pavlov

Russian physiologist

• Born: September 26, 1849; Ryazan, Russia
• Died: February 27, 1936; Leningrad, Soviet Union (now St. Petersburg, Russia)

Winner of the Nobel Prize in Physiology or Medicine in 1904, Ivan Pavlov was one of Russia’s most prominent physiologists. Best known for his investigation of the conditioned reflexes of animals, Pavlov was a skilled surgeon and clinician whose experiments greatly influenced both modern physiology and psychology.

Also known as: Ivan Petrovich Pavlov

Primary field: Biology

Specialty: Physiology

Early Life

Ivan Petrovich Pavlov was born on September 14, 1849, in Ryazan, a small village in central Russia. His father was a local priest who encouraged Pavlov to join the clergy. In 1864, at the age of fifteen, Pavlov entered the Ryazan Theological Seminary. While attending the seminary, Pavlov secretly began reading science essays and books such as Charles Darwin’s On the Origin of Species (1859) and Ivan Sechenov’s Refleksy golovnogo mozga (1863; Reflexes of the Brain, 1965). These works had a strong impact on Pavlov, and, in 1869, he left the seminary to pursue a scientific education at the University of St. Petersburg, where he studied animal physiology.

Pavlov’s mentor, Élie de Cyon, was an expert surgeon who persuaded Pavlov to concentrate his studies on the heart and digestive system. Under Cyon’s direction, Pavlov developed surgical precision that was admired by his colleagues. Pavlov received the university’s gold medal for his work on a research project concerning the pancreatic nerves. After graduating in 1875, Pavlov entered the Military Medical Academy in St. Petersburg to work as an assistant in Cyon’s laboratory. Pavlov resigned this post, however, after Cyon was dismissed by the academy’s administration. For the following two years, Pavlov studied at the Veterinary Institute in St. Petersburg.

In 1877, he went to Breslau, Germany (now Wroclaw, Poland), to work with Rudolf Heidenhain, a specialist in digestion. After receiving his medical degree in 1879, Pavlov went on to receive his postdoctoral degree from the University of St. Petersburg in 1883. He was awarded another gold medal for his doctoral dissertation, which described the nerves that control the heart. In 1881, Pavlov married Serafima Vasilievna Karchevskaia. The couple had four sons and a daughter.

Pavlov returned to Germany in 1884 to work with cardiovascular physiologist Carl Ludwig. For the following two years, he collaborated with both Ludwig and Heidenhain. In 1888, Pavlov was invited to direct an experimental physiological laboratory in St. Petersburg. During this period, Pavlov became interested in “nervism,” the manner in which the central nervous system affects reflexes. In 1890, he was appointed professor of physiology at the Russian Imperial Medical Academy. A year later, he became director of the Department of Physiology at the Institute of Experimental Medicine. There, he conducted the majority of his research until he resigned from the academy in 1924.

Life’s Work

Throughout his career, Pavlov challenged many of the accepted practices of his contemporaries. At the time Pavlov conducted his experiments, physiologists commonly relied upon vivisection, the dissection of live animals, in their research. Pavlov disagreed with this practice for both ethical and scientific reasons. Pavlov argued that, in addition to the suffering that animals experienced during vivisection, the procedure created stress in the animal subjects that altered their physiological reactions.

Using his surgical expertise, Pavlov developed methods to reduce the trauma experienced by animal subjects. Rather than vivisecting his subjects, Pavlov surgically altered animals in order to observe their nervous responses under relatively normal conditions over long periods of time.

In one experiment on a dog, Pavlov performed surgery to prevent the food that the animal had eaten from reaching the stomach. Pavlov used this experiment to demonstrate that digestive glands in the dog’s stomach still released digestive acids even though no food actually made its way to the stomach. As a result, Pavlov was able to demonstrate that part of the digestive process in the stomach was controlled by stimulation of the dog’s vagus nerve (one of the brain’s major cranial nerves) rather than the actual presence of food in the stomach. In 1904, Pavlov received the Nobel Prize in Physiology or Medicine for this research.

By the time Pavlov accepted the Nobel Prize, he was already involved in the study of conditioned reflexes. While studying the digestive processes of dogs, Pavlov performed operations on his animals that allowed him to collect the saliva they produced when fed. The amount of saliva produced was measured at various stages of feeding, and the saliva’s chemical properties were analyzed. While performing these experiments, Pavlov noticed that some dogs began to salivate before they were actually given food.

Pavlov called this reaction “psychic secretion” and believed that the dogs were responding to other stimuli such as the food’s smell. He conducted experiments in which food was placed at different distances from the test animals, and discovered that some dogs began to salivate even when no food was presented. Pavlov concluded that the dogs were responding to environmental factors that they had learned to associate with food, such as the appearance of the laboratory assistants who fed them.

Pavlov considered the presence of food an unconditioned stimulus, because the dogs’ reactions to it occurred naturally and did not have to be learned. Under these circumstances, the dogs’ salivation was considered an unconditioned reflex. Alternately, he concluded that the appearance of the laboratory assistants was a conditioned stimulus, because the animals had learned to associate the staff with feeding. When the assistants appeared but did not provide food, the dogs’ salivation was considered a conditioned reflex, because it was a response that did not occur naturally, but one that had been learned through association.

The study of conditioned reflexes became a major component of Pavlov’s research. In order to reduce the number of external influences, Pavlov isolated some of the dogs and began to pair unrelated stimuli (such as sounds and flashing lights) with their feeding, which was now done by machine. He discovered that a neutral stimulus (such as the ringing of a bell) could become a conditioned stimulus and could produce a conditioned reflex (such as salivation) if the neutral stimulus was consistently paired with an unconditioned stimulus (such as food).

Pavlov’s breakthrough led to a whole field of study known as classical conditioning, in which Pavlov tested how animals reacted to subtle changes in their environments. As a result, Pavlov was able to draw conclusions about higher cerebral functions in animals. By applying this knowledge to additional experiments in which the animals were surgically altered, Pavlov was able to develop a general theory about how the brain’s major hemispheres function.

Impact

Although Pavlov considered himself a physiologist, his work also had an enormous impact on psychology. His book Conditioned Reflexes (1927) delineates the basic principles of classical conditioning. These theories were modified by John B. Watson and the behaviorist school of psychology to explain how anxieties and other disorders arise from previous associations, and how maladaptive behaviors could be extinguished through positive and negative reinforcement. Classical conditioning has also been applied to business management, prison reform, military training, education, advertising, and a variety of other fields.

In 1924, some of Pavlov’s animals nearly drowned when his laboratory was flooded. Pavlov noticed that several animals never recovered from this trauma, concluding that people could also respond to negative events in unusual ways. Most notably, he theorized that some schizophrenics become withdrawn because they associate external stimuli with potential danger. Based on Pavlov’s theory, the Soviet government (Russia having become the Soviet Union in 1922) began to institutionalize patients in calm environments that provided little stimulation.

Throughout his career, Pavlov imposed rigorous control over his staff. He anticipated modern clinical practices by carefully designing experiments and by relying on assistants to conduct research and to interpret results. Although he was a strict supervisor, Pavlov was loyal to his associates. Highly critical of the Soviet regime, he openly opposed many political practices, using his influence to assist colleagues persecuted by the government. He died in Leningrad on February 27, 1936.

Bibliography

Babkin, Boris P. Pavlov: A Biography. Chicago: U of Chicago P, 1949. Print. Written by one of Pavlov’s pupils, including personal anecdotes and information gathered from both A. A. Savich, one of Pavlov’s colleagues, and Pavlov’s widow.

Pavlov, Ivan Petrovich. Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex. Trans. G. V. Anrep. New York: Dover, 1960. Print. One of the best translations available of Pavlov’s key lectures. Contains an extensive bibliography.

Saunders, Barbara R. Ivan Pavlov: Exploring the Mysteries of Behavior. Berkeley Heights, NJ: Enslow, 2006. Print. Written for a juvenile audience. Considers his early life and highlights his primary scientific contributions. Includes a time line, glossary, and bibliography.

Todes, Daniel P. Ivan Pavlov: Exploring the Animal Machine. New York: Oxford UP, 2000. Print. Concise biography designed to provide high school students and other readers with an introduction to Pavlov’s life, ideas, and scientific discoveries.

---. Pavlov’s Physiology Factory: Experiment, Interpretation, Laboratory Enterprise. Baltimore: Johns Hopkins UP, 2002. Print. Examines Pavlov’s early work in physiology by focusing on the structure and operations of his laboratory in the Physiology Department of the Institute of Experimental Medicine. Describes the role the institute and its employees played in Pavlov’s research and discoveries.