Ivan Petrovich Pavlov
Pavlov, Ivan Petrovich
Pavlov, Ivan Petrovich
RUSSIAN PHYSIOLOGIST, PSYCHOLOGY RESEARCHER
ST. PETERSBURG UNIVERSITY, 1875; IMPERIAL MEDICAL ACADEMY (A.K.A. MEDICAL-SURGICAL ACADEMY), MD, 1879
Although he won the Nobel Prize for his research on the physiology of the digestive system of dogs, Ivan Pavlov left his most lasting legacy in psychology. In a career that spanned nearly seven decades, Pavlov discovered the basic concepts behind associative learning in both animals and humans. His theory of conditioned reflexes, or "training" individuals to respond to a neutral stimulus, laid the groundwork for behavioral psychology and associative learning theory. In addition, his work on experimental neuroses, or behavioral and thought problems caused by conditioning techniques, explained the causes of some mental disorders and, more importantly, helped develop effective behavioral therapy methods.
Pavlov began to study conditioned reflexes after conducting research on the digestive system of dogs. He discovered that his laboratory dogs would salivate after hearing a sound or other sensory stimulus that they had learned to associate with food, even if no food was present. Pavlov conducted meticulous and extensive studies into this phenomenon. He also pioneered new laboratory techniques.
Influenced in part by British naturalist Charles Darwin, Pavlov theorized that conditioned reflexes served as a survival mechanism. He reasoned that animals must adapt quickly to changes in their environment in order to stay alive.
He also believed that his conditioning experiments could help him better understand both the physiology and functioning of the brain. Pavlov believed that all nervous activity was based on the principals of excitation and inhibition. Individuals with strong and balanced excitatory and inhibitory responses were less likely to behave abnormally.
Throughout Pavlov's lifetime, his homeland of Russia experienced political and social upheaval. Because Pavlov worked and lived in the capital city of Saint Petersburg, he witnessed the changes firsthand. Pavlov spoke out frequently against the government, despite the fact that other protesters were being arrested and killed. It is a testament to his scientific prestige that he could openly criticize the Communist government while being financially subsidized by it.
Ivan Petrovich Pavlov was the eldest of 10 children born into a family with deep religious roots. His father, Petr Dmitrievich Pavlov, belonged to the sixth generation of Pavlov men appointed as local parish priests in the Eastern Orthodox Church. Ivan's mother, Varvara Ivanovna Pavlova, was a priest's daughter. With religion so deeply ingrained in both the family lineage and in the culture of their native village of Ryazan, his parents expected Ivan to be one of the seventh generation of Pavlov priests.
Pavlov's mother suffered from headaches, hair loss, and various skin conditions during his childhood; her symptoms were termed a "nervous disorder." Pavlov's colleagues have speculated that her condition may have motivated Pavlov to study psychopathology, the neurological basis of neuroses and psychoses.
As a child, Ivan enjoyed spending time outdoors; he especially liked working in the family garden with his father. At the age of eight, Ivan suffered injuries after falling from a high fence. He was weakened from the experience and recovered slowly. Discouraged by his continued illness, his family sent him to recover at the nearby Saint Trinity's Monastery, which was overseen by Pavlov's godfather. Through a rigorous schedule of daily exercise, chores, and other activities, Ivan regained his health. He also discovered a love for reading that would be nurtured by his father's extensive library. Pavlov was schooled at home until the age of 11.
Ivan entered the Ryazan Theological School in 1860. Four years later, he graduated and began studying for the priesthood at the Ryazan Theological Seminary. He was an excellent student, and the discipline he had gained from his experience at the monastery helped him to adapt easily to the rigors of academic life.
But his passion for reading and learning, along with the social changes that were sweeping Russia under the regime of Tsar Alexander II, would soon call Ivan away from a life in the priesthood. Seminarians were allowed to read only books that agreed with Eastern Orthodox doctrine; Pavlov's insatiable appetite for the written word and his budding interest in science, however, led him to sneak frequently into the Ryazan library. Ivan started a kruzhok, or discussion group, with other seminary students to discuss previously banned books and political journals that the government had recently re-released to the public. Many of these were science books, as the government was attempting to strengthening Russia's research programs. Pavlov's contemporaries perceived the materialism of science as an alternative to the mysticism of the church, necessary to support Russia's progress (see "Historical context").
As Ivan approached his final year at seminary, he made a critical decision that would affect not only his relationship with his family but also the fields of physiology, learning theory, and psychology. Much to his father's dismay, Pavlov left the Ryazan Theological Seminary to apply for entrance into St. Petersburg University. The university's faculty boasted many scientific luminaries and the campus was located next door to the prestigious Academy of Sciences. Pavlov began his studies there in 1870. He had difficulty coping with the demands of city and university life, however; before completing his first year of study, Ivan returned home suffering from nervous exhaustion. After the summer, however, Ivan returned to St. Petersburg accompanied by his younger brother Dmitry, who was entering the university's chemistry program.
Dmitry became Ivan's roommate and, although he was the younger of the two, he usually took care of Ivan. With his brother's support, Ivan began to flourish academically and socially. He joined a new kruzhok and chose a field of specialization—physiology.
Ivan's first mentor at St. Petersburg, physiologist Ilya Fadeevich Tsion, was well-known for his skilled surgical techniques in animal vivisection. Under his tutelage, Ivan won a gold medal for his work on the nerves of the pancreas.
In 1873, Tsion became the youngest-ever professor of physiology at the Imperial Medical Academy; he received the prestigious appointment at the age of 29. Tsion offered Ivan a lab assistant position, which Pavlov eagerly accepted. Tsion's tenure would be short-lived, however. His conservative social, religious, and political views caused controversy among his peers, who believed that everything could ultimately be explained through rigorous scientific experimentation. Moreover, Tsion thought physiologists could not study topics such as thought processes or emotions; his temperament alienated his colleagues, and he was a demanding teacher. Because Tsion was Jewish, he also faced anti-Semitism. Protests against his appointment reached their peak after Tsion flunked half of his sophomore physiology class. Both the Academy and St. Petersburg University were temporarily shut down as students demonstrated against the professor; eventually, the administration bowed to the pressure and removed Tsion from his post in 1874. Pavlov was devastated by the news.
After Tsion's departure, Pavlov went to work in the laboratory of Professor Ustimovich at the Veterinary Institute from 1876 through 1878. Instead of anesthetizing the dogs to insert a catheter that would be used to measure blood pressure, Pavlov first trained the animals to lie still. He then performed the procedure quickly and almost painlessly, without using anesthesia or causing stress to the dog.
Pavlov traveled to Breslau, Germany in 1877 to study the pancreas and digestive system. The following year, Professor Sergei P. Botkin hired Pavlov as his laboratory director. In addition to his career as a distinguished scientist, Botkin also served as personal physician to the tsar's wife. In Botkin's lab, Pavlov developed his theories of nervism—the idea that all physiological processes are somehow related to actions of the central nervous system.
In December of 1879, Pavlov graduated from the Medical-Surgical Academy, earning honors and a gold medal for his work on the circulatory system, and he was awarded a four-year postgraduate fellowship. That same year, Pavlov met a young teaching student and social activist, Serafima Vasil'evna Karchevskaia. As the school term ended, they began to write to each other; shortly after Serafima returned to St. Petersburg, they decided to marry. The wedding would not occur until 1881, however, after Ivan finished his doctoral work and Serafima had spent a year traveling and teaching the poor to read.
- Lectures on the Work of the Digestive Glands. Translated by W.H. Thompson. 1897. Reprint, London: Griffin, 1902.
- Lectures on Conditioned Reflexes: Twenty-Five Years of Objective Study of the Higher Nervous Activity of Animals. Translated by W. Horsley Gantt. 1923. Reprint, New York: International, 1928.
- "Lectures on the Work of the Large Hemispheres of the Brain." (1827) Experimental Psychology and Other Essays. New York: Philosophical Library, 1957.
- Psychopathology and Psychiatry. Translated by S. Belsky and D. Myshene. New Brunswick, NJ: Transaction, 1994.
- Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex. Translated and edited by G.V. Anrep, 1927. Reprint, Mineola, NY: Dover, 2003.
In Botkin's lab, Pavlov researched the cardiovascular system of dogs. His experiments led to his 1883 doctoral dissertation "The Centrifugal Nerves of the Heart," in which he established that cardiac nerves played a part in regulating heart rhythm. Except for a two-year hiatus in Europe during 1884–86 to conduct research related to his fellowship, Pavlov directed Botkin's lab until 1890.
Pavlov's first child, Wirchik, was born in 1883 during a time of financial hardship. After the young family moved in with Serafima's sister in order to make ends meet, Wirchik became ill and died. Both parents were devastated by the loss; two years later, Serafima gave birth to a second son that the couple named Vladimir. Eventually, two more sons, Viktor (1892) and Vsevolod (1893), and a daughter, Vera (1890), joined the family. Unlike Ivan, who turned away from his father's profession, three of Pavlov's children would pursue careers in various scientific disciplines (the fourth studied law).
Pavlov finally received a teaching post in 1890, becoming chair of pharmacology at the Military-Medical Academy. Five years later, he would be appointed chair of physiology at the same institution, a position he would hold until 1925. He was happy to leave Botkin's lab, which he considered limiting due to its small size, poor equipment, and unsanitary conditions. Also in 1890, a wealthy cousin of the tsar decided to fund a new medical research facility. After his first choice for director refused the post, he appointed Pavlov to run the physiological department of the Imperial Institute of Experimental Medicine. Pavlov would remain in that position for 45 years until his death in 1936.
In 1893 the Institute received a generous donation from Swedish inventor and philanthropist Alfred Nobel. This additional funding allowed Pavlov to equip his laboratory to perform experiments on animals that were still conscious, the technique he had pioneered early in his career. The Institute also offered surgical and recovery suites for the lab animals, separate experimental areas, and sterile equipment.
Most of Pavlov's work at the Institute focused on the physiology of the digestive system, primarily investigating the interaction between the central nervous system and digestion. He liked to experiment on dogs, citing their low cost, accessibility, intellect, and the similarity of their digestive systems to those of humans. In 1897 Pavlov published his findings in a collection called "Lectures on the Work of the Main Digestive Glands," which earned him international acclaim.
Pavlov conducted feeding experiments on dogs that had received esophagotomies (a surgical procedures that severs the esophagus so that ingested food never reaches the stomach, a process known as sham feeding) and gastric fistulas (a hole in the stomach that contains a feeding tube). He found that dogs that were sham-fed produced more gastric juice and saliva than dogs that were fed through a fistula. This important result demonstrated that stimulating the nerves in the mouth was an essential part of the digestive process. Pavlov also discovered that dogs that were allowed to feed themselves digested their food better than dogs that had food placed directly into their mouths. Therefore, he showed that the psychological influence of appetite also influenced the digestion.
One of the greatest innovations Pavlov made in the field of physiology and animal experimentation was waiting until after his animals healed from surgery before testing his theories. His contemporaries performed vivisection on an anesthetized animal and then measured the physiological results immediately afterwards. By contrast, Pavlov performed vivisection and then waited for the dog to heal. He was the first scientist to recognize that the physiological stress of the vivisection procedure sometimes influenced the outcomes of an experiment.
A skilled surgeon, Pavlov also made great advances in vivisection techniques. For example, he developed a procedure known as "the isolated stomach" that created a separate small pouch, or second stomach, with all its nerve connections intact. The isolated stomach, which was accessible to researchers through a fistula in the abdominal wall of the dog, could be used to measure reactions to food via the amount of gastric juice it secreted, even though food never entered it.
At a conference in Madrid in 1903, Pavlov gave a lecture entitled "The Experimental Psychology and Psychopathology of Animals." This speech was his first public discussion of the theory of conditioned reflexes. The following year, at the age of 55, Pavlov was awarded the Nobel Prize in Physiology or Medicine for his research on the digestive system. He was the first physiologist, and the first Russian, to receive the prestigious award. While accepting the prize, Pavlov elaborated even further on the psychological theories he had first introduced at the Madrid congress. He asked:
What now is the physiologist to do with the psychical phenomena? Disregarding them is impossible since in the action of the salivary glands, in which we are interested, they are closely connected with the purely physiological phenomena. If, nevertheless, the physiologist wants to study them, he finds himself faced with the question: How?
Pavlov would devote the rest of his career to delving into the interrelationship of the psychical (or psychological) with the physiological through studying conditioned and unconditioned reflexes. His findings in this area of research remain important nearly a century later.
Pavlov was awarded membership in the Russian Academy of Sciences in 1907. Between his work at the Institute of Experimental Medicine (IEM), the Medical-Military Academy, and the Physiological Laboratory at the Academy of Sciences, Pavlov had dozens of physiology students and medical doctors working under his direction. In fact, between 1891 and 1917, over 110 individuals passed through Pavlov's lab at the IEM alone.
To further refine his experiments, Pavlov designed a new laboratory facility that was completely soundproof. This lab also featured equipment that allowed him and his assistants to control every aspect of an experiment without coming into contact with their subjects, the dogs. Construction on the "Tower of Silence" was completed in 1913.
Pavlov's work suffered a setback over the next decade, as Russia experienced massive political and social upheaval with the outbreak of World War I, the Bolshevik uprising, the October Revolution, and the Russian civil war (see "Historical context"). Pavlov suffered personal losses as well; his eldest son Viktor died of typhus and his younger son Vsevelod, who had joined the White Army during the civil war, was forced to leave the country after its defeat. The Pavlov family was left nearly destitute, food was scarce, and lab work had ceased.
In the summer of 1920, Pavlov wrote a letter to the head of the Bolsheviks (later called the Communist Party), Vladimir Lenin. He explained his current circumstances and requested permission to leave the country to continue his work. In response to the threat of losing an important academic resource and national icon like Pavlov, Lenin responded decisively. He issued a government decree in January of 1921 that stated that "In view of Academician I. P. Pavlov's outstanding scientific services, which are of tremendous importance to the working people of the world," Pavlov would receive lifetime housing and rations for his family and full funding for publication of "a deluxe edition of the scientific work prepared by Academician Pavlov, summing up the results of his research over the past 20 years." In addition, Pavlov's flat and laboratory would be equipped with "every possible facility." Lenin also appointed a special commission devoted solely to ensuring that Pavlov's research could continue under "the best conditions."
The Communist Party continued to supply Pavlov with everything he needed for his research, even though he openly criticized the government's religious persecution and political arrests. Pavlov frequently used his influence to free other scientists from imprisonment.
An act of nature in September 1924 paved the way for one of Pavlov's biggest discoveries in the emerging field of conditioning. Heavy rains caused the Neva River to swell beyond its banks, and floods swept the streets of St. Petersburg (by then renamed Leningrad). Pavlov's dogs had to be rescued from their kennels, and they swam to the nearby main laboratory building, where they were kept until the danger passed. Pavlov reported that "All this produced a very strong and obvious inhibition in all the animals, since there was no fighting or quarrelling among them whatever, otherwise a usual occurrence when the dogs are kept together." After the floodwaters had receded and experiments resumed, Pavlov and his colleagues discovered that the conditioned reflexes in some of the dogs had disappeared, apparently as a result of the trauma.
Pavlov soon theorized that traumatic experiences could also trigger psychoses and neuroses in humans. In Conditioned Reflexes, Pavlov stated that
a development of a chronic pathological state of the hemispheres can occur from one or other of two causes: first a conflict between excitation and inhibition which the cortex finds itself unable to resolve; second the action of extremely powerful and unusual stimuli.
Pavlov had begun working with human psychiatric patients in 1890 as part of his investigative work on the actions of the cerebral cortex. In the 1920s, for his ongoing research into ways that the physiology of the brain and nervous system triggered mental illness, Pavlov attended seminars at Leningrad's Neuropsychiatric Hospital and the Balinskiy Psychiatric Hospital. Here, psychiatrists presented neurotic and psychotic patient case studies and Pavlov analyzed the patient's history, interviewed the patients, and recommended a course of treatment based on what he considered the cause of their neurosis or psychosis. Pavlov took a special interest in schizophrenia, which he likened to a "chronic hypnotic state." In the early 1930s, he studied dozens of schizophrenic patients at the psychiatric clinic of the Balinskiy Hospital.
At the youthful age of 80, Pavlov received a substantial grant from the Soviet government for a new laboratory: an entire dog village located on the outskirts of Leningrad. The Koltushi compound was fully outfitted for Pavlov's new line of research, known as eugenics. Eugenics was the science of improving the genetic stock of the human race by breeding out "inferior" qualities; it has since been discredited and is considered unethical today. The scientific theory dovetailed with the socialist ideals of the Soviets. Pavlov wanted to find a way to scientifically isolate the conditions necessary to create a dog with an ideal nervous temperament. He believed that the controlled environment of Koltushi would allow him and his staff to isolate the environmental and hereditary factors that determined the temperaments in the dogs he would raise there.
A big believer in brisk exercise, Pavlov remained more physically active than some men half his age and continued to work long days in his labs. (Besides winning the Nobel Prize as well as recognition from the Russian Academy of Sciences, he also received many other honors, including an honorary doctorate from Cambridge University, the Order of the Legion of Honour from the government of France, and honorary memberships in scores of medical societies.) In August of 1935, Pavlov helped to bring the Fifteenth International Physiological Congress, an esteemed gathering of physiologists from around the world, to the Soviet Union. Pavlov was honored by his fellow physiologists, and he was recognized as the preeminent leader in the field in an address by Scottish physiologist George Barger. Six months after the congress, Pavlov developed pneumonia. He died on February 27, 1936, and scientists from the Soviet Union and around the world mourned the passing of a scientific icon.
Even though his specialty was physiology, most experts consider Pavlov's contributions to psychology, specifically those related to conditioned reflexes, to be his greatest legacy.
Reflexes themselves were not a new concept. In his "Lectures on Conditioned Reflexes," Pavlov notes that the idea of man as a machine governed by complex nervous reflexes originated with French philosopher and mathematician René Descartes three centuries earlier. Several of Pavlov's contemporaries also had explored the reflexive properties of the nervous system. Pavlov's work, however, is based on the physiology of the brain, and therefore it is, as he puts it, a "purely objective investigation into the highest nervous activities."
Pavlov was particularly influenced by the work of his eminent Russian colleague Ivan Sechenov. Sechenov wrote Reflexes of the Brain, and he was considered one of the founders of objective (i.e., materialist-based) psychology. Sechenov asserted that all mental processes, or "psychic phenomenon," were reflexive actions (or reactions) of the nervous system. In experiments with frogs, he was able to inhibit muscle reflexes by placing salt crystals on the animal's brain. Sechenov also suggested that reflexes might somehow be reshaped or changed, but he never tested his hypothesis in the lab. Pavlov used Sechenov's theory to experimentally demonstrate the phenomenon of classical conditioning.
Pavlov was the first to empirically demonstrate the existence of a "mind-body" connection; that is, to show that mental and emotional variables can have affect physical processes of the body. The learning theory that evolved from Pavlov's findings on conditioned reflexes became known as classical conditioning. Conditioning helps to explain the ways in which some people develop seemingly irrational fears and anxieties or associate certain smells and sounds with a specific place or situation. The theory even discusses why a dog barks and becomes agitated when the doorbell rings.
Through his work on the nervous system and cerebral cortex, Pavlov also was one of the first scientists to explore the role of personality and temperament in physiological reactions. Despite well-controlled conditions and precise measurements, not all dogs would react exactly the same to an identical stimulus, even when allowances were made for different physical characteristics. Furthermore, Pavlov discovered that certain temperament types were more prone to psychopathological conditions than others.
Pavlov conducted extensive experimentation that involved removing portions of the brains of dogs to establish that the cerebral cortex was related to reflexive reactions. He published his findings in his 1927 book entitled Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex.
Pavlov believed that all of what was considered "psychic" phenomenon, which had previously been explained only in terms of abstract introspective processes such as psychoanalysis, could be explained through careful physiological experimentation. In his 1904 Nobel lecture, Pavlov stated the scope of his vision:
Essentially only one thing in life interests us: our psychical constitution, the mechanism of which was and is wrapped in darkness. All human resources, art, religion, literature, philosophy and historical sciences, all of them join in bringing light in this darkness. But man has still another powerful resource: natural science with its strictly objective methods.
Main points Through Pavlov's work on the physiology of the digestive system, he discovered that digestive processes could be triggered even before food passed a dog's lips. Just showing food to a hungry dog could cause the animal to begin to salivate and secrete gastric juices. Why did these external factors cause these reactions, or reflexes? The dogs had previously learned through experience that the appearance of a bowl of kibble meant they would be eating shortly, so the sight of food cued their digestive systems to start up. This finding was Pavlov's first indication that what he called "psychic" influences (i.e., thoughts, emotional states, personality) could have a direct bearing on physiological processes.
Pavlov had already demonstrated that the taste of food in a dog's mouth stimulated the animal's oral nerves in such a way that salivation was triggered, an involuntary physiological reaction he called an unconditioned response. But Pavlov and his colleagues soon discovered that by repeatedly presenting a completely unrelated and neutral stimulus (e.g., the ringing of a bell, the click of a feeding device, or the beat of a metronome) to the feeding process, they could eventually trigger salivation in the dog with the neutral stimulus alone. Pavlov called this reaction a conditioned response, or reflex, and the process by which it was achieved was called conditioning.
Explanation In his Nobel lecture, Pavlov explained his theory of unconditioned (or physiological) and conditioned (or psychic) reflexes:
The difference between the two reflexes is firstly that our old physiological reflex is constant, unconditioned, while the new reflex continually fluctuates and, hence, is conditioned. . . in the conditioned reflex, however, those properties of the object act as stimuli that in themselves have no direct relation at all with the physiological role of the saliva.
In other words, conditioning involves pairing a neutral stimulus (or conditioned stimulus) with an unconditioned stimulus to create a conditioned response. Dogs that were exposed to a particular sound (the conditioned stimulus) each time they were given food (the unconditioned stimulus) eventually began to associate the bell with eating and would salivate at the sound of the bell. A conditioned reflex had been created in those dogs.
Does a conditioned reflex occur every time a neutral stimulus is presented with an unconditioned stimulus? No. Usually, the pairing must be repeated several times before conditioning takes hold; the number of repetitions depends upon the subject and the stimuli. A profound event or a very novel stimulus may require fewer pairings (also called trials). The conditioned response is dependent on the intensity of the stimulus itself.
An American psychologist who founded the field of psychology known as behaviorism, John Broadus Watson (1878–1958) believed that psychological study should be based on observable reflexes and behavior only instead of introspection of the subconscious mind.
Watson entered college at the age of 16, and received his Ph.D. from the University of Chicago in 1903 at the age of 24. His dissertation involved work with learning behaviors culled from maze experiments with white rats. In 1908 he joined Johns Hopkins University, where he was appointed a professor and made director of the psychological laboratory.
In 1913, Watson delivered a lecture at Columbia University (which was later published in Psychological Review) entitled "Psychology as the Behaviorist Views It." This work, which would become known as the "behaviorist manifesto" in later years, asserted that the only valid study of psychology was that of observable states and not of the introspection of "states of consciousness" that dominated the field at the time. This work was followed a year later by his text Behaviorism: An Introduction to Comparative Psychology, which built on Pavlov's conditioned reflexes and outlined Watson's stimulus-response theory of behavior.
Watson was elected president of the American Psychological Association in 1915 at the age of 36, making him the youngest person ever to hold that office. Around this time, his research focus shifted to infants and children. Watson believed that all human emotion was rooted in three reactions—fear, rage, and love—that were not innate but rather conditioned. Through a now infamous experiment with a white rat and an 11-month-old boy named "Little Albert," Watson conditioned the boy to be afraid of a white rat by banging on a metal bar loudly with a hammer and frightening him each time he reached for the animal. Albert quickly became fearful at the sight of the rat alone.
Later, he discovered that Albert subsequently transferred this fear-response reaction to another stimulus, also becoming afraid of a white rabbit with which he had previously played. This phenomenon of developing a conditioned response to a stimulus that is different from but similar to the original stimulus used in conditioning came to be known as generalization.
While at Johns Hopkins, Watson also did substantial consulting work for organizations as diverse as the Baltimore and Ohio Railroad and the Social Hygiene Board of the U.S. government. His distinguished career in academia came a sudden end in 1920 after a scandal involving an affair with a research assistant. Watson subsequently divorced his wife and married graduate student Rosalie Rayner, and he was asked to resign his professorship at Johns Hopkins.
By 1924, Watson had become a vice president at J. Walter Thompson, one of America's largest ad agencies, where he remained until 1935. Here he helped develop and refine a number of groundbreaking strategies that persist in the field today, including market research of the motivations behind consumer brand loyalty and testimonial advertising. Watson continued to write on behavioral psychology, making the field more accessible to the general public. He participated in applied psychology projects while working in the ad world; for example, he was one of the first proponents of personality testing for prospective employees in the corporate world.
Watson wrote a popular book entitled Psychological Care of the Infant (1928) that was based on his observational studies of infants and his theories of behavioral psychology. He believed that proper conditioning of the child was the key to forming healthy personality traits.
In 1935, Watson left J. Walter Thompson to continue his advertising career at the William Esty Company, where he remained until his retirement in 1945. The APA awarded Watson a gold medal for his contributions to psychology in 1957. One year later, he passed away at the age of 80.
A unique or novel neutral stimulus is more likely to cause a conditioned response than a common one. For example, a woman who split up with her boyfriend while a certain song was playing on the radio may forever identify that particular tune with heartache. But if a telephone was also ringing at the same time, the less "novel" stimulus of a ringing phone would be less likely to trigger an emotional response in the future.
Finally, Pavlov believed that the neutral stimulus had to be contiguous (that is, occur at the same time or in close proximity to) the unconditioned stimulus in order for a conditioned response to develop. Later research has found that conditioning is most effective when the conditioned stimulus is presented just before the unconditioned stimulus, and when both stop at the same time.
Pavlov discovered that conditioned reflexes could be reversed if the neutral stimulus was presented enough times in the absence of the unconditioned stimulus. He explains the process, known as extinction, in the context of his study on salivating dogs and food: "On the other hand promptly active signals can lose their stimulating effect if repeated over a long period without bringing the object concerned into contact with the oral mucous membrane." Extinction would prove to be a useful psychological finding to treat phobias and other irrational fears.
Extinction of a behavior was not always permanent, however. Pavlov found that conditioned responses that were extinguished could spontaneously recur later (spontaneous recovery). One of Pavlov's dogs had been conditioned to salivate at the sound of a bell. Pavlov extinguished the reflex by repeatedly exposing the dog to the bell without the presence of food or feeding. Although the conditioned reflex was gone, Pavlov found that some time later, it suddenly reappeared when the dog was exposed to the sound of a bell. The response was weaker (less salivation), but it was still present.
Conditioned reflexes could also be temporarily interrupted if extra stimuli were introduced, either on purpose or unintentionally. In Conditioned Reflexes, Pavlov described how a co-worker would call him into their work area to demonstrate a dog's newly acquired conditioned reflex, only to have the dog fail to perform. The reason was Pavlov's presence itself; he was what he termed a temporary inhibitory stimulus; his presence triggered the dog's investigatory reflex and temporarily distracted it (what one might call a sense of curiosity, although Pavlov did not like to attribute human characteristics to his dogs).
Pavlov also developed the concept of higher-order conditioning, which involved pairing one neutral stimulus previously associated with a conditioned response with a second neutral stimulus. In higher-order, or second-order conditioning, a conditioned stimulus (A) is first paired with an unconditioned stimulus until a conditioned response is achieved. Then a second conditioned stimulus (B) is paired with the first conditioned stimulus (A). Even though the unconditioned stimulus is never presented with stimulus B, it is able to achieve a conditioned response simply by its association with the stimulus A.
Examples Pavlov's drooling dogs are the most famous example of classical conditioning. A bell is rung immediately before or as food is served to a dog. With repetition, the dog eventually salivates at the sound of the bell only. Pavlov used a number of different neutral stimuli in his conditioning experiments, including the beat of a metronome, flashes of light, odors, and skin stimulation. When the bell was rung repeatedly without the presence of food (or feeding of the dogs), the conditioned response would eventually disappear.
Many dogs will also show a classically conditioned response to the sound of a doorbell. The dog knows that the sound of the bell means a visitor has arrived, because the sound of the bell has preceded a guest's presence many times before. So when the doorbell rings, the dog runs to the door, wags his tail, and perhaps even barks in response, even though he cannot see who or what is on the other side. In fact, even if the interior bell is located far from the front door, the dog will still run to the door because he knows from experience the visitor will appear here.
If someone plays ding-dong-ditch (rings the doorbell and runs away before the resident anwers the door) a few times, however, the dog may get a little less excited about the sound of the bell. And some dogs may also react to the sound of the phone, because they have generalized their conditioned response to the doorbell stimulus to apply to similar stimuli (in this case, all bells). For more on generalization, see "John Watson" sidebar.
The influence of classical conditioning is quite commonly seen in house pets. Any cat owner knows that the sound of a can opener will trigger a feline frenzy. Why? Because the owner has conditioned the cat to associate the sound of a can being opened with dinnertime.
For humans, conditioning can often be seen as phobias and irrational fears. Prior bad experiences associated with places, people, activities, or things can condition individuals to develop fearful or anxious reactions to neutral events or objects. For example:
- A man who was stuck in an elevator for 12 hours develops a fear of confined spaces.
- A child who is repeatedly dunked in the pool by a mean-spirited peer grows into an adult with a swimming phobia.
- A woman who was abused by her ex-husband when they lived in a small apartment over a music store is gripped by fear whenever she hears the sound of piano music.
Pavlov believed that the theory of classical conditioning could help eradicate neuroses and psychoses as well as explain their origins.
Temperament and psychiatric disorders
Main points For Pavlov, temperament of both animals and humans is determined by the interplay of what he called excitatory and inhibitory responses. As the names suggest, excitation stimulates nervous reaction while inhibition suppresses it. Through his studies of the nervous system of dogs, Pavlov developed the theory that abnormalities in behavior and temperament occur when excitation and inhibition are either out of balance or when both processes are very weak. Dogs that had strong excitatory and inhibitory responses that were in equilibrium were the most easily disciplined; those dogs also responded the best to conditioning. Pavlov called their temperament type strong.
In those animals for which both excitation and inhibition were weak or were out of balance with each other, behavioral problems and neuroses were common. Pavlov found that these dogs were not able to deal appropriately with environmental stimuli. Pavlov called this type of dog inhibitable, or weak. An animal's ability to adapt quickly to a changing environment, called mobility, also influenced its temperament type.
Pavlov's theory of temperament types was rooted in the ancient concept made famous by the Greek physician Galen of four humors: choleric, melancholic, sanguine, and phlegmatic. The Greeks believed that the balance of the four humors (which corresponded to yellow bile, black bile, blood, and phlegm) determined an individual's personality type. The relative quantities of the humors created warm versus cool and dry versus moist (which were related to the elements of fire, air, earth, and water). A person with an excess of yellow bile was choleric (warm and dry—also easily excitable and hot-tempered), one with an abundance of black bile was melancholic (cool and dry—also inhibited and pessimistic), someone with excess blood was sanguine (warm and moist—also confident and energetic), and finally, one with abundant phlegm was phlegmatic (cool and moist—also calm and hard-working). In Pavlov's system, the choleric temperament is analogous to the excitable type, the melancholic to the inhibitable type, and the phlegmatic and sanguine to the strong type.
Of course, Pavlov realized that the human personality was slightly more complex than the personalities of the dogs he studied. He believed human behavior was determined by three factors:
- second signal system (language)
- temperament (as determined by excitation and inhibition)
The first signal system is conditioned reflexes—instinctual behaviors learned through experience with one's environment. Pavlov also realized that, unlike his dogs, human beings also had a second set of signals at their disposal—language—or what Pavlov called "the signals of signals." In his view, personality was determined by which signal system was dominant in an individual. Those who reacted predominately to environmental stimuli rather than language were called artists, while those for whom language was a greater motivator were termed thinkers. Rarely, someone would have equal strength in both areas; Pavlov called these people "intermediate" types.
- artists = first signal system over second signal system
- thinkers = second signal system over first signal system
Furthermore, Pavlov believed that the different personality types were prone to certain psychological disorders based on their reaction to their environment. Thinking types were predisposed to obsessions and phobias, while artistic types leaned towards hysteria and outbursts. Whether or not these disorders manifested themselves depended on an individual's ability to cope with environmental stress or trauma.
Explanation Pavlov found that neuroses could actually be induced in the lab in those animals with weak and unbalanced temperaments. Strong negative stimuli could cause experimental neuroses by overwhelming the animals' inhibitory or excitatory processes. Stimuli that were difficult to differentiate from previously introduced stimuli could also cause behavioral problems. Neurotic behaviors might be removed through counter-conditioning techniques or by extinction of the conditioned response. Pavlov also experimented with the use of bromide drugs to return dogs to a non-neurotic state.
Pavlov's physiological experiments on the brain function of his animal subjects also influenced his theories on personality and psychopathology. He held that the basic drives, emotions, and instinctual behavior, or unconditioned reflexes, were regulated in the subcortex area of the brain in both animals and human beings. Immediately above the subcortex, in the cerebral hemispheres, Pavlov believed could be found the "signal systems" that helped regulate temperament and subsequently behavior. He associated the first signal system (conditioned reflexes) with the cerebral hemispheres (excluding the frontal lobes) and the second signal system (language) with the frontal lobes.
In a 1932 work entitled "Essay on the Physiological Concept of the Symptomatology of Hysteria," Pavlov describes how the activity that takes place in each of these brain areas determines the temperament type of the individual:
In the artist the activity of the cerebral hemispheres, while developing throughout their entire mass, least of all involves the frontal lobes and concentrates mainly in other parts; in the thinker, on the contrary, it is most intense in the frontal lobes.
Pavlov had a special research interest in schizophrenia, and he studied many patients with the disorder at the Leningrad Clinic. He theorized that schizophrenia was the result of both a weak temperament type and childhood trauma. Because of schizophrenics' weak inhibitory responses, the trauma overwhelms them and damages their nervous system.
Examples One of Pavlov's students, N. R. Shenger-Krestovnikova, was the first researcher to describe the role of sensory discrimination in producing neuroses. Shenger-Krestovnikova performed an experiment that conditioned a dog to salivate whenever it saw a light projection of a circle (that is, a visual image of a circle was paired with food). At the same time, the dog was conditioned to have an inhibitory response when it was presented with an ellipse (that is, the sight of an ellipse was followed by no food). Then Shenger-Krestovnikova gradually changed the shape of the ellipse to become more circular. Eventually, the dog could not discriminate the circle from the ellipse, and it lost all conditioned responses to both circles and ellipses. The dog also demonstrated behavioral problems, such as whining and struggling, when presented with the task. Pavlov believed that the neurotic behavior in the dog was produced by a clash between the inhibition and excitation responses of its nervous system. Two stimuli that were once unique had become too similar for the dog to differentiate between; the result was an induced neurosis.
Pavlov and his associates also pioneered the use of negative or painful stimuli in experimental conditioning. Another Pavlov student, M.N. Eroféeva, used an electric shock as a stimulus before presenting food, thereby conditioning the dog to associate the shock with food (as evidenced by its salivary response) without reacting defensively (growling or barking). Initially, the shock was always applied to the same part of the dog's body. Later, when Eroféeva administered the shock to another part of the dog's body, the conditioned response disappeared and the dog acted defensively. This experiment proved to Pavlov and his colleagues that neurotic or maladaptive behavior—in this case, the loss of defensive reflexes when the subject was placed in a painful or dangerous situation—could be induced in the laboratory. Perhaps more importantly, this finding laid the groundwork for the concept that the conditioning of neurotic behavior could be reversed, a method known as counter-conditioning.
Hypnosis, sleep, and cortical inhibition
Main points Pavlov devoted considerable time to the study of sleep and hypnosis; he considered both states as forms of progressive "cortical inhibition" of the nervous system. Representing them as two points along a continuum, Pavlov portrayed sleep as complete, diffuse internal inhibition of the cortex and hypnosis as a "partial sleep" state.
According to Pavlov, certain conditioned reflexes, such as the salivation response, remained in his animal subjects during hypnosis, while other reflexes related to movement disappeared. Pavlov concluded that the reflexes that remained did so either because they were governed by the subcortex rather than the cortex, or because the state of hypnosis was light and did not significantly inhibit the cortex.
Explanation In Pavlov's lecture "Conditioned Reflexes: Pathological Disturbances of the Cortex," he discussed experiments in which a dog was hypnotized by applying a physical restraint or by placing the animal on its back. According to Pavlov,
[t]he inhibitory influence of very strong stimuli can be regarded as a reflex of 'passive self-defense,' as, for instance, in the case of hypnosis. The immobility of the animal makes it less noticeable to the enemy, and thus abolishes or diminishes the aggressive reaction of the enemy.
Pavlov also described the use of "strong and unexpected stimuli" to induce hypnosis in cases of "hysteria" in man.
Strong stimuli were not the only triggers of a hypnotic response. Pavlov also described other "external stimuli which directly lead to inhibition of the cortical elements. These are of three kinds—monotonously reoccurring weak stimuli, very strong stimuli, and unusual stimuli." Repetitive, recurring conditioned stimuli gradually lulled dogs to sleep in several of Pavlov's experiments.
Pavlov believed hypnotic conditioning of humans was very similar to that of animals: According to Pavlov, "The classical method consisted in the performance of so-called 'passes'—weak, monotonously repeated tactile and visual stimuli, just as in our experiments upon animals." At present the more usual method consists in the repetition of some form of words, describing sleep, articulated in a flat and monotonous tone of voice. Such words are, of course, conditioned stimuli that have become associated with the state of sleep. In this manner any stimulus that has coincided several times with the development of sleep can now by itself initiate sleep or a hypnotic state. The mechanism is analogous to the inhibitory chain reflexes.
Pavlov also addressed the concept of hypnotic suggestion in terms of conditioned response. He theorized that because language is a excitatory stimulus,
[t]he command of the hypnotist, in correspondence with the general law, concentrates the excitation in the cortex of the subject (which is in a condition of partial inhibition) in some definite narrow region, at the same time intensifying (by negative induction) the inhibition in the rest of the cortex and so abolishing all competing effects of contemporary stimuli and of traces left by previously received ones. This accounts for the large and practically insurmountable influence of suggestion as a stimulus during hypnosis as well as shortly after it.
In other words, suggestion works because a) it is a novel stimulus and b) language, as Pavlov's "second signal," dominates and overrides all other competing stimuli.
Examples The concept of hypnotic inhibition as a reaction to a new and overwhelming stimulus was described in Pavlov's description of an experimental dog that was brought to a large lecture hall filled with people for a demonstration of the animal's conditioned reflexes. Because of the new location and the large audience, the dog became almost catatonic, and while it exhibited a digestive reflex when a conditioned stimulus was presented, it refused to take the food that was presented. A short time later, it fell asleep in its stand. Pavlov explained that the conditioned reflex remained because the dog was in a hypnotic state due to the unfamiliar stimulus of the lecture hall. After a time, the animal's diffuse inhibition had spread throughout the cortex and subcortex, triggering sleep.
Pavlov also related the story of a dog that was left in its stand (or experimental harness) for hours at a time between experiments. Eventually, the dog would shift into a hypnotic or pre-sleep stage immediately upon entering the experimentation room, and it would fall asleep within ten minutes if the experiment was not begun. It had been conditioned to associate the monotony of the room with the inhibited sleep state.
Russia during Pavlov's lifetime was in constant turmoil. He lived through the reigns of four tsars, a world and civil war, a revolution, and two socialist governments. When Pavlov was born in 1849, Russian society was on the cusp of significant change. Since medieval times, Russia had been bound by a rigid class structure: many poor serfs ruled by a few wealthy, land-owning aristocrats, all of whom were subject to a supreme ruler called the tsar.
Tsar Nicholas I ruled Russia from 1825 to 1855. Near the end of his reign, his army suffered a devastating defeat in the Crimean War, eventually surrendering to France and England in 1856. Nicholas' son and successor, Alexander II, had to bear the burden of his father's failures. In order to return Russia to international prominence, Alexander initiated the Great Reforms, which included rapid industrialization, infrastructure improvements, and removal of censorship restrictions. Most importantly, Alexander II also became a great patron scientific research. For young students such as Pavlov, this abandonment of state-sanctioned censorship and support of science was very exciting.
In order to ensure the success of his reforms, the tsar decided to abolish serfdom. In 1861, he granted freedom to the approximately 50 million Russian serfs, much to the chagrin of the landed nobility. With greater Russian freedoms and relaxed censorship, public discussion of a wide range of issues became commonplace. Journals were published that covered virtually every aspect of Russian life. The availability of these journals, and books such as Charles Darwin's On the Origin of Species and G.H. Lewes Practical Physiology, inspired Pavlov's interest in science.
A failed 1879 assassination attempt caused Alexander to roll back many of the reforms he had instituted during the previous two decades. Alexander appointed six military governor-generals to enforce a stringent censorship system. He banned controversial books throughout Russia, and arrested and imprisoned many critics of the government.
The renewed repression intensified revolutionary opposition to Alexander's government. A second assassination attempt succeeded in 1881, and the new tsar, Alexander III, vowed to stamp out all revolutionary activities and regain governmental control. He reduced access to education, established 'land captains' to beat the peasantry for committing minor offenses, and exiled or executed members of revolutionary groups. Even with this dramatic shift in public policy, however, Russian industrialization grew at a faster rate than that of any other European nation during the 1890s.
Despite the booming economy, however, working and living conditions in the urban areas were deplorable. Newlyweds Ivan and Serafima Pavlov suffered from these difficulties; one of Pavlov's biographers reported that the couple once found their infant son covered in lice. Ivan's later appointment to the Institute of Experimental Medicine, however, would improve their lifestyle considerably.
After the death of Alexander III in 1894, the last tsar of Russia assumed the throne: Nicholas II. Famine became commonplace and discontent rose throughout the nation. Once again, revolutionary groups began to grow in size and strength.
One such group, the Social Democrats, formed in 1898 to foster a revolution by the Russian working class. In 1903, this organization split into two opposing factions: the Mensheviks and the Bolsheviks. The Mensheviks, led by George Plekhanov, believed that all Russians should be eligible for membership and that all members should be given a voice in the party policy. The Bolsheviks, led by Vladimir Lenin, believed that the party should contain only a few highly dedicated and intelligent revolutionaries. This group would conceive and implement all legislation on behalf of the people. The Bolsheviks wanted to overthrow the tsar and establish the working class (the proletariat) as the ruling class of Russia, completely eliminating the nobility (the bourgeois).
Despite the rise of revolutionary groups, Nicholas II did nothing to alleviate the social and economic burdens facing his nation The situation continued to deteriorate until a major strike was called in St. Petersburg in July 1914. Within days however, on August 1, 1914, World War I broke out. A new wave of patriotic support postponed revolutionary activity for a while.
The Russian army that entered World War I was pathetic. Starvation, military ineptitude, and tremendous loss of life in the world war sparked the final Russian revolution in March 1917. Nicholas II was forced to abdicate and a provisional government was established, led by Aleksandr Kerensky. Kerensky's government disappointed most members of the proletariat, mainly because of it did not enact genuine land reforms or withdraw from the war.
The Russian scientific community, however, was primarily pleased with the political changes. Under the tsar, the development of new institutions and acquisition of funding had been slow and difficult. Not only had the Kerensky government promised additional support for scientific research, it had also appointed several leading scholars to commissions that were designed to expand Russia's academic and scientific scope.
Over the the next eight months, many revolutionary organizations and anarchists attempted to overthrow Kerensky. Then, on November 7, 1917, the great October Revolution erupted. (The Russians used a different calendar than the rest of the world, and so they were a few days behind.) Led by Bolshevik leader Vladimir Lenin, the rapid coup d'etat overthrew the Kerensky government and immediately led to several dramatic reforms.
Following the October Revolution, the Russian Academy of Sciences (of which Pavlov was a member) met to discuss their options in dealing with the new Bolshevik government. Most academy members were disappointed that the advances that the Kerensky government had promised would never materialize. They also did not trust the Bolsheviks' political motivations. Nevertheless, the general assembly of the academy decided to enter into negotiations with the Bolsheviks. Pavlov was one of only two academy members who voted against the proposal, advocating a boycott of the Bolsheviks instead.
On the evening of July 16, 1918, several Bolsheviks stormed the house where the tsar and his family were being held and executed them all.
As did most Russians, Pavlov and his family found life during wartime difficult. The Bolsheviks searched Pavlov's home several times between 1918 and 1920, and he and his son were even arrested for a brief period. Scientific experimentation ground to a halt as supplies and food became scarce and many of Pavlov's colleagues and students left university to fight in the war.
By 1922, the Bolsheviks had solidified their control over the new Soviet Union. In part because of the Russian Academy of Science's swift acceptance of the Bolshevik government, the Academy's doors remained open. The Bolsheviks, believing that a strong science program was essential to building the socialist state, generously funded research and established prestigious awards, such as the Lenin Prize, for individual scientific achievements.
Yet the relationship between the government and science faced some challenges, especially in Pavlov's case. In 1931 the state planning committee ordered the Academy members to compile detailed work plans. Many members, objected, however, citing concerns such as practicality (scientific discoveries could not always be held to a deadline) and productivity (a predetermined agenda could hamper theoretical exploration). Pavlov simply refused to comply. Pavlov also strongly opposed many other government initiatives, including the Politburo's insistence in 1927 that the Academy should elect communist members. Pavlov and others argued that membership should be determined by scientific merit only and not political affiliation. The fact that he could defy the authorities with so little repercussion proved his esteemed position and reputation within the Bolshevik government.
Moreover, the Soviets greatly valued Pavlov's scientific theories on conditioning. They dovetailed nicely with the government's concept of humans as mechanistic—biological machines that could be understood and controlled through science. In addition, the the Soviet military employed knowledge gained from Pavlov's experimental work on neuroses and the physiological mechanisms underlying hypnosis.
Pavlov's work on conditioned reflexes earned him international scientific recognition and great prestige in his homeland; as Russia's only Nobel Prizewinning scientist in a field, physiology, that was highly regarded by the Communist government, he was considered a national treasure. But as a physiologist working in the realm of psychology, he faced some unique challenges within the scientific community. Ironically, however, Pavlov's psychological theories have stood the test of time more readily than have his physiological theories of brain function.
In Conditioned Reflexes, Pavlov discussed "the close connection between physiology and psychology," something he recognized that many psychologists in Russia and America did not acknowledge or appreciate:
I am convinced that an important stage in the development of human thought is approaching, a stage when the physiological and the psychological, the objective and the subjective, will really merge, when the painful contradiction between our mind and our body and their contraposition will either actually be solved or disappear in a natural way.
Of course, advances in neurological research and imaging have provided a much clearer understanding of the workings of the frontal lobes and other sections of the brain about which Pavlov theorized. He was correct in his assessment that the subcortex region of the brain regulated autonomic and instinctual functioning. Later re-searchers have found that conditioning of some subcortical functions may also be possible.
While Pavlov was partially right in his supposition that the frontal lobes were involved in processing language (the "second signal"), researchers now know that the temporal lobes are primarily responsible for language recognition (left temporal lobe) and speech (right temporal lobe).
Among his contemporaries, Polish researcher Jerzy Konorski criticized certain aspects of Pavlov's physiological work. Konorski was actually a student in Pavlov's lab from 1931 to 1933. He had a strong research interest in the concept of association and the relationship between stimuli and responses. But Konorski found Pavlov's concepts of diffuse inhibitions and theoretical waves of cortical excitation and inhibition centers speculative and inconsistent with his knowledge of neuron theory. Yet the Polish scientist was respectful of Pavlov's contributions to conditioning theory, and he dedicated his 1948 book, Conditioned Reflexes and Neuron Organization, in part to Pavlov.
In 1937 Konorski published a paper with S. Miller to present their ideas on classical versus instrumental conditioning to the growing behaviorism movement in America. They had trained a dog to lift its foot in response to a cue in order to receive a food reward. Konorski and Miller explain that "[i]n conditioned reflexes of the first type, the reaction is effected by organs innervated through the central or autonomic nervous system, while, in conditioned reflexes of the second type, the effector can probably be only a striate muscle." In other words, the conditioning was formed through the conscious actions of the dog itself, not through external stimuli triggering a reflex, as Pavlov had surmised. Konorski also developed the idea of avoidance conditioning in later works.
Some additional concepts about the interrelationship between stimuli in conditioning that have been
Clark Hull and Kenneth Spence
Clark L. Hull (1884–1952) and Kenneth Wartinbee Spence (1907–67) met at Yale University, where Hull was a professor of psychology and Spence was a graduate student and research assistant in the primate lab of Robert Yerkes. Hull and Spence shared an interest in experimental psychology, researching maze learning in the rat. Although the two men jointly authored only one published paper, they created one of the most influential learning and conditioning theories of their time—the Spence-Hull theory.
The Spence-Hull theory attempted to quantify the way behavior was learned by using a mathematical equation, or model. It also elaborated on the concept of conditioned and unconditioned motivation in behavior formation. Environmental cues can condition motivation; strong environmental events, such as an electric shock, are an unconditioned source of behavioral drive.
Both Hull and Spence were considered part of the neobehaviorist movement, along with their contemporaries B.F. Skinner and Edward Tolman. Neobehaviorism was founded on Pavlovian conditioning, but the field also explored the role of motivation and environment in forming behavior. Hull, Spence, and others developed complex associative learning theories that were typically tested on laboratory animals.
The concept of drive reduction theory as an essential part of learning was developed by Hull. Drive reduction theory held that behavior was motivated by basic drives, or instinctual needs, such as hunger and sexual desires. When an individual responded to those drives (for example, by obtaining and eating food to satisfy hunger), the drives were reduced. This reduction in basic drives consequently served as a form of reinforcement for the behavior that fulfilled them. This was tied to Hull's idea of "habit strength," that the reinforced behavior would be self-perpetuating as long as the drive was satiated by the behavior. Both habit and drive strength elicit what Hull calls "reaction potential," or the likelihood that a response or behavior will occur again. Hull combined all of his ideas into a series of complex mathematical theorems and formulas designed to explain behavior.
Hull wrote Principles of Behavior in 1943, in which he stated that the strength of a fear response corresponds directly with the level of negative reinforcement. He also discussed ways by which negative reinforcements increase fear and anxiety. For example, repeatedly avoiding an anxiety-provoking situation, such as public speaking, can actually heighten the anxiety response.
Clark Hull earned his Ph.D. from the University of Wisconsin in 1918 after doing undergraduate work at the University of Michigan. Hull joined Yale's Institute of Human Relations in 1929, and was elected president of the American Psychological Association in 1936. He also did extensive research into both psychometric testing and the field of hypnosis, publishing Aptitude Testing (1929) and Hypnosis and Suggestibility (1933). Hull remained at Yale until his death in 1952.
Beyond his association with Hull, Spence is best known for his theory of discrimination learning, published in the Psychological Review in 1936. The theory explained how animals choose, or discriminate, between two or more stimuli that are presented at the same time, selecting the one that produces a reward.
Kenneth Spence received his Ph.D. from Yale in 1933. He was awarded a four-year fellowship to the Yale Laboratories of Primate Biology at Orange Park, Florida. In 1938, he took a faculty position at the State University of Iowa, where he taught for over two decades. In 1956, Spence received the Distinguished Scientific Contribution Award from the American Psychological Association. He moved to the University of Texas in 1964, and three years later he succumbed to cancer at the age of 59.
developed and refined since Pavlov's original work include:
- Cue competition. The interplay of two conditioned stimuli presented simultaneously with an unconditioned stimulus.
- Blocking effect. Initial conditioning to stimulus A alone prevents or minimizes conditioning to stimulus B when A and B are presented together. This idea is rooted in Pavlov's concept of overshadowing, which said that if stimulus A is stronger or more novel than stimulus B, even if both are presented simultaneously, stimulus B will create minimal conditioning (that is, A will overshadow B).
- Differential conditioning. The concept that an animal can learn to discriminate between two different but similar stimuli if one is presented with some sort of reinforcement.
At the start of the twentieth century, Pavlov's ideas on conditioning and stories of his laboratory investigations began to spread beyond Russia. First came Pavlov's Nobel Prize; in 1906, he gave a lecture in the United Kingdom at Charing Cross Hospital on "The scientific investigation of the psychical faculties or processes in the higher animals" that was published in the noted American journal Science. Researchers Robert Yerkes and Sergius Morgulis also published a review of Pavlov's lab work that was printed in The Psychological Bulletin in 1909.
But it was the publication of G. Anrep's English translation of Pavlov's lectures on conditioned reflexes that really brought Pavlov's theories on conditioning to the attention of American scientists. His work had a significant impact on learning theorists and the fledgling psychological field of behaviorism, attracting the attention of behavioral psychologists such as B.F. Skinner.
Although he built on Pavlov's work in conditioned reflexes and acknowledged the Russian scientist's major contributions to the field, American behavioral psychologist B.F. Skinner (1904–90) diverged from Pavlov's theories on two fronts. First, he did not believe that Pavlov could accurately determine the physiologic structure and nature of the nervous system simply by examining the behavior of his experimental subjects. In other words, he believed that physiology and behaviorism were completely separate areas of study that could not be extrapolated from each other. Secondly, Skinner was more interested in behavior as a reaction to environment, where choice and consequences reinforce behavior.
Skinner went on to delve deeper into the concepts of operant conditioning outlined by Konorski and Miller in their earlier work. He explained the differences between the two approaches: "In the Pavlovian experiment, however, a reinforcer is paired with a stimulus; whereas operant behavior is contingent upon a response." Reinforcers in an operant conditioning experiment only appear when the subject has made the correct behavioral "choice." The wellknown "Skinner box" provided an environment for lab animals to learn how to receive food by pressing a lever. Within the box, different simultaneous stimuli (e.g., light and dark, sounds) provided additional operant stimuli. Skinner used different forms of positive and negative reinforcement to shape an animal's behavioral choices.
Beyond behaviorism, Russian psychologist and learning theorist Lev Vygotsky applied Pavlov's conditioning theory to the process of language development, or "second signaling" system. Vygotsky hypothesized that children acquired language through imitation and interaction with adults. Eventually, a child's internal concept or picture of what a word symbolizes becomes her conditioned stimulus for language.
The neuropsychologist Alexander Luria, a student of Vygotsky's, used the concept of "semantic conditioning" to establish a conditioned reflex to a word and then investigated whether words that were similar in structure or sound would elicit the same reflex. For Luria, internal conceptualizations of words (that is, "inner speech") were temporary mental associations that were flexible and therefore easily modified and revised with experience. This theory was in contrast to the rigid mental associations formed by conditioning in animals that Pavlov had inferred.
During the summer of 1950, the Russian Academy of Sciences the Academy of Medical Sciences held a joint session and issued a directive to their members that Pavlov's scientific principles should guide all future research work. This edict significantly limited research freedom, and several scientists were removed from their posts and publicly denounced for espousing non-Pavlovian theories. Among those discredited were Russian physiologist I.S. Beritov, who had disagreed with Pavlov's concept of inhibition in the forming of conditioned reflexes, instead surmising that reflexes resulted from spontaneous electrical activity in the brain. Also removed from his position as director of the Institute of Physiology of the Academy of Medical Sciences was Pyotr K. Anokhin, a former student of Pavlov's who had attempted to refine his theory of the reflex arc of the conditioned reflex. This display of political muscle and restriction of scientific autonomy would have greatly distressed Pavlov himself, had he been alive to witness it, and it significantly hampered Russian research initiatives.
THEORIES IN ACTION
Pavlov's rigorous scientific method, innovative experimentation techniques, and aseptic (sanitary) laboratory environment revolutionized the way animal research was performed; many of his methods remain in widespread use today. Pavlovian conditioning continues to be a methodological and conceptual foundation for psychological research and learning theory—the benchmark by which behavioral animal experiments are designed.
Behavioral therapy, which emerged in the 1950s, also owes a tremendous debt to Pavlov's theories of conditioning. The concept of conditioning gave psychologists a way to uncover the etiology, or causes, behind certain phobias and neuroses. Pavlov's theories on experimental neuroses have also laid the foundation for modern behavioral-based treatment of psychiatric disorders such as panic and anxiety disorders and phobias. Behavioral therapy is based on the concept of replacing undesirable or maladaptive conditioned responses (such as irrational fear) with a positive and appropriate conditioned response (such as relaxation). Gradually, the positive response should replace or extinguish the maladaptive one. Cognitive-behavioral therapy (CBT), an offshoot of behavioral therapy, also uses behavioral techniques supplemented by an increased awareness of the causes behind the maladaptive behavior.
The behavioral-based treatment method of systematic desensitization—the process of eliminating fear or anxiety by gradual and constant exposure to the source of fear—is rooted in Pavlov's findings that learned conditioned behaviors could also be extinguished, or unlearned. The technique was developed by psychiatrist Joseph Wolpe in the 1950s. Relaxation exercises are usually used as part of systematic desensitization techniques to further eliminate feelings of anxiety by introducing a substitute conditioned stimulus to associate with the source of the fear. For example, someone who is afraid of the water can overcome the fear by gradual exposure to a pool coupled with deep muscle relaxation techniques. Each time the person enters the pool and does not experience something terrible, the learned association between water and bad feelings is eroded.
Aversive therapy is another offshoot of Pavlovian theory. It involves pairing a highly negative stimulus with a harmful stimulus to eliminate a maladaptive behavior. Aversive therapy is used frequently in the treatment of alcoholism. One form of aversive therapy is the use of disulfarim (Antabuse), a drug that triggers extreme nausea and vomiting when combined with alcohol. In a technique called "taste aversion therapy," an individual may be put through several sessions at which they are given the drug and then given alcohol to smell and drink, making them ill. More frequently, the drug is prescribed to individuals that are newly recovering alcoholics as a prophylactic to prevent relapse.
Stimulus control therapy (SCT), commonly used in treating sleep disorders, is also based in classical conditioning theory and is a form of counter-conditioning. This treatment is based on the idea that insomnia is actually a self-perpetuating learned response that is caused by an individual's association of their bedroom with sleeplessness and anxiety. In SCT, the sleep environment is carefully controlled—the individual is instructed to leave the room for a period of time when they are unable to sleep, to have a fixed waking time each day, and to avoid any activities in the bedroom that aren't related to sleep or sex.
Modern learning theory continues to build on Pavlovian conditioning. Researchers have developed models of associative learning that examine the relationship between multiple conditioned stimuli. Pavlov's theories of personality also have influenced later behaviorists. German-born psychologist and statistical researcher Hans Eysenck built on Pavlov's idea that excitation and inhibition activity determines temperament. Eysenck theorized that personality is predetermined by both genetics and by the physiological balance of cortical arousal and depression. Eysenk's "dimensions" of temperament were neuroticism and introversion-extroversion (the latter being his interpretation of inhibition and excitation). Later, he also added psychoticism to his theory. Neuroticism was determined by the level of activity in an individual's sympathetic (or autonomic) nervous system; neurotic behaviors, such as anxiety or panic attacks, were caused by hyperactivity of this area of the brain.
The Pavlov Department of Physiology at the Institute of Experimental Medicine continues his research tradition, conducting animal and human studies in the department's three laboratories. For example, in the Laboratory of Psychophysiology of Emotion, researchers investigate anxiety, depression, and other emotional disorders. Victor Klimenko, the department's director since 1995, reports that:
Nowadays the phenomenon of reinforcement is the central point in different theories of emotions and behavior. Main principles of forming conditioned reflexes—a specially directed control of emotional state—are employed by staff during investigations of purposeful activity of dolphins in free behavior.
At the Institute's Clinical Laboratory of Neurodynamic Correction of Psycho-Neurological Pathology, researchers study how conditioned reflexes cause childhood behavior, and how deficits in emotional reinforcement and environmental feedback can trigger neurological problems. At the Laboratory of Neurobiology of Integrative Brain Function, scientists continue to map the complex interrelationships and functions of the brain through both the analysis of conditioned reflexes and behavior and via research on biochemical regulation of the brain.
A fear of dentists is a common phobia that often is conditioned by societal messages but also may be rooted in other experiences. A 2002 case report in the Journal of Clinical Psychology described a 39-year-old woman ("Carly") who had a phobia of dental work that started at the age of eight, when a dentist slapped her after she tried to get out of the chair during a procedure. She had avoided dentists ever since; consequently, she had to have half of her teeth surgically removed due to neglect. Clearly, this traumatic childhood experience had conditioned her anxious response to the dentist's office. Carly received a deconditioning therapy known as Eye Movement Desensitization and Reprocessing (EMDR), which couples a stimulus, such as eye movement or finger tapping, to redirect attention from the anxiety-provoking stimulus (in this case, the dentist) and remove any negative associations. At the end of the treatment period, Carly reported significantly less anxiety, and she was able to proceed with dental treatment.
Two case studies reported in Virtual Environments in Clinical Psychology and Neuroscience described a unique treatment approach of systematic desensitization—the use of virtual reality simulations (called virtual reality therapy, or VRT). The first was a 32-year-old woman who underwent eight 30-minute sessions of VRT that simulated the experience of flying over an urban area. Her anxiety level, which was high at the initiation of VRT, was gradually reduced and had declined significantly enough to allow her to undertake "real-world" long-distance flights by the end of her therapy. The second subject, a 42-year-old man, underwent five sessions of VRT. Although he experienced emotional anxiety and physical symptoms (such as sweaty palms) at the start of each session, the researchers reported that subjective and objective measures of his anxiety level would decrease significantly as the session progressed. At the end of the treatment, the subject was able to fly with minimal anxiety.
1849: Born in the village of Ryazan, Russia.
1870: Leaves the seminary to enroll at St. Petersburg University
1875: Begins physiology studies at the Medical Academy
1879: Graduates from the Academy; wins a gold medal in student competition.
1881: Marries Serafima Vasil'evna Karchevskaia, a teacher.
1897: Publishes "Lectures on the Work of the Main Digestive Glands."
1904: Awarded the Nobel Prize in Physiology or Medicine.
1910: Construction of "Towers of Silence" begins.
1917: The October Revolution occurs; the Bolsheviks take power and Vladimir Lenin becomes new Soviet leader.
1921: Lenin issues special decree giving Pavlov full funding and supplies for his research and living expenses.
1927: Publishes "Lectures on the Work of the Large Hemispheres of the Brain."
1929: Construction of Pavlov's research facilities at Koltushi begins.
1936: Dies on February 27 after developing pneumonia at the age of 86.
Conditioning is also used to eliminate behaviors or habits considered undesirable for health reasons. Behavioral and cognitive-behavioral techniques are frequently used in smoking cessation programs. Other less dangerous but unwelcome habits, such as nail-biting, can also be extinguished through these techniques. A study in Psychological Reports describes a 32-year-old woman that underwent systematic desensitization in order to eliminate her nail-biting habit. During the 28-day study, she completed interviews and self-reporting questionnaires that uncovered the triggers of anxiety that caused the nail-biting behavior. Through techniques of muscle relaxation and meditation, she learned to replace the negative behavior with positive stress-reduction techniques when faced with anxiety.
The ways in which behaviors are conditioned in infancy and even before birth continue to be a rich source of study for psychologists. Animal studies, in particular, frequently use conditioning techniques to explore how prenatal and neonatal environments affect development. A 2004 study in the journal Developmental Psychobiology reported on a classical conditioning experiment with a chimpanzee fetus. The chimp fetus was exposed to a combination of vibro-acoustic (that is, sound vibration) stimulation and two specific tones of different frequencies. Tone A was always followed by the VAS (the unconditioned stimulus), while tone B was never followed by the VAS. After birth, when the tones were presented to the chimp, it could differentiate between the two, and it responded more excitedly to tone A.
Relevance to modern readers
Pavlov's influence is so far-reaching because conditioning forms an integral part of people's lives. Learning through association—either consciously or unconsciously—is part of the essence of humanity. Behaviors and attitudes are shaped by a person's life experiences, or conditioning. A man's ongoing preference for a suit that he was wearing when he landed his last job, a woman's aversion to a food that made her extremely ill in the past, a boy's fear of wasps as a result of a previous bee-sting—all of these are common examples of the ways in which conditioning, reinforcement, generalization, and aversion affect common aspects of everyday life.
An example of conditioning in modern society is popular advertising. The creative forces behind print and broadcast advertising know that associating a product with popularity, beauty, money, and love can make the public identify that product with those desirable traits (even when it has nothing to do with them). Young people should drink a certain soda because a beautiful pop star does, kids should wear a designer's clothes because the coolest kids do, and moms should serve the best brand of rice because it means they love their families. Fear may also be invoked and associated with brand identity; without the "right" insurance protection, car, stockbroker, or health plan, families will be left penniless. In short, brands become attractive not simply because they represent inherently good products, but because they become associated with some other appealing characteristic.
Boakes, Robert. "The Impact of Pavlov on the Psychology of Learning in English-Speaking Countries." The Spanish Journal of Psychology 6, no. 2 (November 2003): 93–98.
Catania, A. Charles and V. Laties. "Pavlov and Skinner: Two Lives in Science." Journal of the Experimental Analysis of Behavior 72, no. 3 (1999): 455–61.
David-Fox, Michael and György Péteri, eds. Academia in Upheaval: Origins, Transfers, and Transformations of the Communist Academic Regime in Russia and East Central Europe. Westport, CT: Bergin & Garvey, 2000.
De Jongh, A. et al. "Efficacy of Eye Movement Desenstization and Reprocessing in the Treatment of Specific Phobias: Four Single-Case Studies on Dental Phobias." Journal of Clinical Psychology 58, no. 12 (2002): 1489–503.
Kawai, N. et al. "Associative Learning and Memory in a Chimpanzee Fetus: Learning and Long-Lasting Memory Before Birth." Developmental Psychobiology 44, no. 2 (March 2004): 116–22.
Klimenko, Victor and J.P. Golikov. "The Pavlov Department of Physiology: A Scientific History." The Spanish Journal of Psychology 6, no. 2 (November 2003): 112–20.
Kreshel, Peggy. "John B. Watson at J. Walter Thompson: The Legitimization of 'Science' in Advertising." Journal of Advertising 19 (1990).
Lenin, V.I. "Concerning the Conditions Ensuring the Research Work of Academician I.P. Pavlov and his Associates." Lenin's Collected Works Vol. 32. Moscow: Progress Publishers, 1965. Marxist Internet Archive Eds. Robert Cymbala and David Walters. [cited April 10, 2004]. http://www.marxists.org/archive/lenin/works/1921/jan/24.htm.
Mackintosh, Nicholas. "Pavlov and Associationism." The Spanish Journal of Psychology 6, no. 2 (November 2003): 177–84.
McClanahan, T.M. "Operant Learning (R-S) Principles Applied to Nail-Biting." Psychological Reports 77, no. 2 (October 1995): 507–14.
North, Max M. et al. "Virtual Reality Therapy: An Effective Treatment for Phobias." In Virtual Environments in Clinical Psychology and Neuroscience. Amsterdam, Netherlands: IOS Press, 1998.
Pavlov, Ivan P. Conditioned Reflexes. Mineola, NY: Dover, 2003.
Pavlov, Ivan P. Psychopathology and Psychiatry. New Brunswick, NJ: Transaction, 1994.
Plaud, Joseph. "Pavlov and the Foundation of Behavior Therapy." The Spanish Journal of Psychology 6, no. 2 (November 2003): 147–54.
Ruiz, Gabriel et al. "Pavlov in America: A Heterodox Approach to the Study of his Influence." The Spanish Journal of Psychology 6, no. 2 (November 2003): 99–111.
Smith, Gerald. "Pavlov and Integrative Physiology." American Journal of Physiology—Regulatory, Integrative, and Comparative Physiology 279, no. 3 (September 2000): 743–55.
Spence, Kenneth W. Behavior Theory and Learning, Selected Papers. Englewood Cliffs, NJ: Prentice-Hall, 1960.
Todes, Daniel. Pavlov's Physiology Factory: Experiment, Interpretation, Laboratory, Enterprise Baltimore, MD: Johns Hopkins University Press, 2001.
Viru, A. "Early contributions of Russian stress and exercise physiologists." Journal of Applied Physiology 92, no. 4 (April 2002): 1378–82.
Nobel e-Museum. "The Nobel Prize in Physiology or Medicine 1904." The Nobel Foundation. [cited April 10, 2004]. http://www.nobel.se/medicine/laureates/1904/index.html.
Windholz, George. "Ivan P. Pavlov: An Overview of His Life and Psychological Work." American Psychologist 52, no. 9 (1997): 941–46.
Wolpe, Joseph, and Joseph J. Plaud. "Pavlov's Contributions to Behavior Therapy: The Obvious and the Not So Obvious." American Psychologist 52, no. 9 (1997): 966–72.
Pavlov, Ivan Petrovich
Pavlov, Ivan Petrovich
Ivan Petrovich Pavlov (1849-1936), Russian physiologist, psychologist, and Nobel prize winner, was born in the city of Ryazan, the eldest in a family of ten. His father was a priest and teacher of Greek and Latin, his grandfather and greatgrandfather were sextons and produce farmers. His great-great-grandfather, Mokey Pavlov, was a freed serf, the son of a serf who had no surname and whose Christian name, Pavel, became the family name of succeeding generations. Pavlov’s mother was also the daughter of a priest, yet was herself illiterate; she was known in the vicinity for her ability to heal jaundice by having her patients gaze steadily at a pike swimming in a tank of water.
Pavlov was enrolled in the second grade of the First Ryazan Parochial School in 1860, at the age of 11 (an injury caused by a fall had delayed his formal schooling), and in the Ryazan Theological Seminary in 1864. He left the seminary a year before graduation to enter the division of natural sciences of the physicomathematical faculty of the University of St. Petersburg in 1870. The radical change in his outlook and career plans appears to have been brought about by his reading of Russian translations of Jacob Moleschott’s Physiologisches Skizzenbuch and G. H. Lewes’s Physiology of Common Life, as well as the writings of D. I. Pisarev, and particularly, I. M. Sechenov’s “Refleksi golovnogo mozga” (“Reflexes of the Brain”; 1863), which Pavlov had managed to digest in his seminary days.
Pavlov was graduated from the university in 1875 and became a student of the Imperial Medicosurgical Academy in the same year. As a university student, he had performed two original experiments, one with V. N. Veliky on “the effect of the laryngeal nerve on blood circulation” and “the afferent accelerators of tachycardia,” the other with M. Afanas’ev on “the nerve supply of the pancreas.” An abstract of the report of the first experiment was published in 1874 in the Transactions of the St. Petersburg Society of Naturalists. Pavlov was awarded a gold medal for his second experiment, a full report of which was published in 1878 in the highly authoritative Pflugefs Archiv fiir die gesamte Physiologie des Menschen und der Tiere.These two experiments substantially foreshadowed Pavlov’s research interests for the next 16 years—innervation of the vascular and digestive systems.
As a student at the academy, Pavlov served first as a research assistant to K. N. Ustimovich in the veterinary division and later as an assistant to Sergei P. Botkin in the clinical division. He was graduated from the academy in 1879 with the unusual record of 11 scientific publications, only two of which were collaborations and seven of which appeared in Pflugefs Archiv. He stayed on at the academy for postgraduate research, continuing his work in the physiological laboratory of Botkin’s clinic. His 77-page doctoral thesis, “Tsentrobezhnye nervy serdtsa” (“Efferent Nerves of the Heart”), appeared in 1883. In 1884 he was accorded the rank of lecturer in physiology and awarded a twoyear foreign travel fellowship that he spent at the laboratory of C. F. W. Ludwig in Leipzig and at that of P. Haidenhain in Breslau (he had visited the latter laboratory earlier, as a student).
In 1890 Pavlov was made professor of pharmacology of the academy and director of the physiological laboratory of the newly founded St. Petersburg Institute of Experimental Medicine. He became professor of physiology in the academy in 1895, holding the post until 1924, when the Soviet Academy of Sciences established a special Institute of Physiology under his direction and began planning the transfer of its laboratories to the village of Koltushi (now named Pavlovo), about twenty miles from Leningrad. The compound of imposing buildings of the Institute was completed in 1935 and has since expanded. Comprising not only outstanding and interrelated research laboratories but also neuropsychic clinics and young children’s experimental schools, Pavlovo is a unique scientific community, centering on what is perhaps man’s leading life science—behavioral change (conditioning) and related neural action. Pavlov was elected a member of the Russian Imperial Academy in 1907, a member of the U.S. National Academy of Sciences in 1908, and a member of the American Philosophical Society in 1932. Hishonoris causa doctorates include those awarded by the universities of Geneva, Vienna, Cambridge, Edinburgh, and Paris. In 1935, at the age of 86, Pavlov was honorary president of the Fifteenth International Congress of Physiology, held in Leningrad.
Pavlov’s 62 years of almost unceasing experimentation (eight days before his death he discussed and directed the conduct of nine experiments on dogs and discussed and interpreted the behavior of five mental patients) illustrate well the scientist’s way of learning—by studying “more and more about less and less/’ His first 16 years of research centered on uncovering the neural mechanism of blood circulation and digestion; by 1890 he had restricted his research almost wholly to the mechanisms of digestion, a fact cited when he was awarded the Nobel prize; and after 1903 he concentrated almost entirely on the study of salivation. As early as his doctoral dissertation, Pavlov had begun to uphold Botkin’s view of nervism—the nervous system in some way affects both normal and pathological activities of the organism. (This doctrine continues to make Russian medicine and physiology distinctive by emphasizing the functional over the organic, becoming over being.) However, Pavlov went much beyond Botkin. He combined nervism with objective associationism,thereby founding a new life-science discipline—“higher nervous activity”—in his own country and laying a firm basis for objective and behavioral psychology and for behavioral sciences in general. His specific physiological discoveries and surgical innovations (e.g., the Pavlov pouch, permitting the collection of pure gastric juice) developed into a general, novel and, to a large extent, revolutionary system of studying normal and abnormal action in man and animals.
In a more specific sense, one might say that almost all of Pavlov’s research revolved around the action of reflexes—in the nineteenth century, unlearned, or what he came to call “unconditioned,” reflexes and in the twentieth century, his famous “conditioned” reflexes [SeeLearning,article oninstrumental learning]. Here he was influenced by a distinctive feature of the life sciences in Russia: Sechenov’s concept of the reflex. Whereas in western Europe and in America the reflex denoted only a special reaction—peripheral, segmental, simple, quick, unconscious, involuntary—Sechenov had made it the essence of all reactions. As early as 1860, in his doctoral dissertation, Sechenov had declared that voluntary reactions are reflexive in nature. He developed this idea into an all-embracing and radical life-science philosophy in his classic “Refleksi . . .” (1863). All significant animal and human reactions, wrote Sechenov, are (a) determined and determinable, i.e., evoked by measurable and controllable physical stimuli and (b) mediated by the nervous system. Hence, they are all reflexes, whether they be simple or complex, peripheral or central, involuntary or voluntary, unconscious or conscious, physiological or psychical. The reflex was set forth not only as the unit of body action but also of body-mind or body-including-mind action. Indeed, present-day Soviet psychologists typically state that Sechenov uncovered the reflex nature of the psyche, meaning thereby that he upheld the materialistic—or physicalistic—philosophy that psychical reactions invariably originate in physical stimulation and invariably are mediated by neural reactions. [See the biography ofSechenov.]
Although Pavlov was fully familiar with Sechenov’s writings, he did not at first realize their full implication. In the 1890s, during his experiments with digestion, he ascertained that glandular secretion is by no means only a function of measurable physical stimulation. However, at that time, he freely used the concept of “psychic secretion,” which, as he wrote later, he had “then contrasted sharply with reflex secretion”; he also spoke of the experimental animals’ “thoughts, desires, and feelings” ( 1955, pp. 83-85.) By 1898, however, Pavlov had deleted from the manuscript of his pupil’s, S. G. Wolfson’s, doctoral dissertation, “The Work of the Salivary Glands,” several paragraphs containing such sentences as the “role of the psyche in salivary secretion is of course undeniable” and the “psyche determines the work of the salivary glands, choosing between acceptable and rejectable substances.” And in 1901 he took similar exception to a psychic interpretation in a dissertation, entitled “Analysis (of the Normal Conditions) of the Work of Salivary Glands in the Dog,” by another of his students, A. T. Snarsky. Pavlov wrote that:
Dr. Snarsky clung to subjective interpretations of the phenomena, but I, taken aback by the fantasy and scientific barrenness of the approach, began looking for another way out of the difficult position. After persistent thought and mental conflict I finally decided that with regard to so-called psychic stimulation I must remain in the role of a pure physiologist, that is, of an objective external observer dealing only with external phenomena and their reactions. . . . The chief stimulus for my decision, although then an unconscious one, arose out of an impression made upon me in my youth by the brilliant monograph of I. M. Sechenov, father of Russian physiology, entitled Reflexes of the Brain (1863). ( 1928-1941, vol. 1, pp. 38-39)
The decision in favor of the objective-physiological approach was fully realized in 1903 in an address before the Fourteenth International Medical Congress. Entitled “Experimental Psychology and Psychopathology in Animals,” the address put forward clearly and cogently the Pavlovian doctrine of unconditioned and conditioned reflexes, forever replacing psychic secretion with conditionedreflex secretion and declaring boldly that: “Vital phenomena that are termed psychic are distinguishable from pure physiological phenomena only in degree of complexity. Whether we call these phenomena psychical or complex-nervous is of little importance, as long as it is realized and recognized that the naturalist approaches them only objectively, leaving aside the question of their essence” ( 1928, pp. 59-60).
This statement combines with two others—first, that “the physiology of the higher nervous system [read: the behavior] of higher animals can be successfully studied only if one completely renounces the indefinite formulations of psychology and stands wholly upon a purely objective ground” ( 1928, p. 75), and second, that “the naturalist has no right to speak of higher animals’ psychic processes [Pavlov’s italics] without deserting the principle of natural science—which is the work of the human mind directed to nature through studies that derive their assumptions and interpretations from no other sources than nature itself” ( 1928, p. 82). These statements were surely clarion calls to behavioral objectivism and were sounded in almost the same form a decade later by John B. Watson, the father of American behaviorism. Yet it must be made clear that Pavlov was not simply a “general behavioral objectivist” but a specific “objective associationist.” His historic contributions inhere not just in advocating the objectification of categories of the mind through behavior categories but in providing a specific objective method of studying the chief traditional explanatory principle of mind—associationism. What had, ever since Aristotle, been merely imaged and meditated on, Pavlov made to flow, so to speak, in capillary tubes and electric batteries. Through the conditioned reflex, the study of association became subject to all the refinements and measurements and means of verification of modern science and technology.
The conditioned reflex
In its original, classical paradigm the conditioned reflex demonstrates that a stimulus initially inadequate to evoke some reflex may become adequate after it has been administered one or more times together with a stimulus adequate to produce the reflex. Pavlov called the inadequate stimulus the conditioned or to-be-conditioned stimulus; the adequate stimulus was called the unconditioned stimulus; the reflex in response to the originally adequate stimulus, the unconditioned reflex; and the reflex in response to the originally inadequate and later adequate stimulus the conditioned reflex. Later, Anatolii G. Ivanov-Smolenskii (1927-1952), working in Pavlov’s laboratory, J. Konorski and S. Miller, in their own and in Pavlov’s laboratory (see Konorski 1948), and Starytsin in Bekhterev’s laboratory, modified the original Pavlovian paradigm. Similarly, in the United States the paradigm was modified and was called instrumental conditioning (Hilgard & Marquis 1940) or operant conditioning (Skinner 1938), and it stimulated a great deal of research and thought in the field. The modified paradigm, however, added little to Pavlov’s empirical laws of, and generalizations about, conditioning, its contribution being more in the realm of expanding theory.
Approximately six thousand successful experiments employing the exact Pavlovian paradigm of pairing unconditioned with to-be-conditioned stimuli have by now been reported. All kinds of organisms, from protozoa to men and from neonates (even fetuses) to the most advanced human and animal seniles, and all kinds of reflexes and stimuli have been used in these experiments. Moreover, conditioning has been related experimentally to almost all other known organismic changes, either as the changes affect the conditioning or as the conditioning affects the changes. To cite two out of hundreds of examples: data from eight experiments are available on the effects of “experimental clinical death” on conditioning, that is, on the fate of conditioned reflexes when an animal is experimentally put to death and then revived (Negovskii 1954); and data from 82 experiments are at hand on the effect of ionizing radiation on conditioning (Voprosy . . . 1962). Reports of conditioning experiments exist in 29 different languages, although the large majority are in Russian and English.
Early in his experimentation Pavlov noted that the study of conditioning yielded sets of interrelated functional laws or generalizations and suggested related sets of testable hypotheses for further laws or generalizations. On such a basis a complete systematic discipline could be erected, and Pavlov gradually proceeded to do so.
The chief functional laws or generalizations concerning empirical conditioned-reflex data established by Pavlov include: (a) extinction, the gradual diminution and final disappearance of a conditioned reflex, when the conditioned stimulus is repeatedly administered without the unconditioned stimulus; (b) spontaneous recovery, the partial reversal of the effects of extinction and regaining of the original conditioning in the course of time—a sort of forgetting of extinction that is greater than the forgetting of the original conditioning; (c) generalization, the partial transfer of a conditioned reflex to stimuli similar to the conditioned stimulus (stimulus generalization) and to reflexes similar to the conditioned reflex (reflex generalization); (d) differentiation, the training that involves alternating presentations of the conditioned stimulus, accompanied by the unconditioned stimulus, with presentations of related stimuli, unaccompanied by the unconditioned stimuli (differential conditioning); (e) higher-order conditioning,the formation of a conditioned reflex through pairing a to-be-conditioned stimulus with a previously conditioned stimulus (instead of an unconditioned stimulus); (f) dynamic stereotypy, the patterning of successively applied conditioned stimuli in such a way that the positional order of each stimulus rather than its specific nature determines the nature and magnitude of the conditioned reflex evoked by the stimulus; (g) disinhibition, the partial regaining of conditioning, when a partially or totally extinguished conditioned stimulus or a partially or totally differentiated similar stimulus is applied together with some new or extra stimulus—putative indication that extinction and differentiation are inhibitory processes that may themselves be inhibited (i.e., disinhibited) by the action of an extra stimulus. Obviously these generalizations are basic to the understanding of the mechanisms of change in human and animal behavior—ways through which the change occurs in normal (and abnormal) life situations, methods and techniques for its full analysis in the laboratory, and means of producing and controlling it through special education.
In the main, Pavlov’s formulations—although not necessarily his whole system—have been verified and accepted. In a glossary in a recent standard textbook on conditioning and learning (Hilgard & Marquis  1961) 36 terms are attributed to Pavlov and only 25 to all other students of the field combined. A perusal of the two current official periodicals of American experimental psychology—the Journal of Experimental Psychology and theJournal of Comparative and Physiological Psychology—reveals that their contributors are still very much concerned with Pavlov’s work, perhaps more so than with the work of any other physiologist or psychologist. A recent survey of members of the American Psychological Association placed Pavlov second only to Freud in the members’ estimate of who most influenced contemporary psychology. And there is no doubt that Pavlov would have ranked first, had the survey been confined toexperimental psychologists.
Conception of higher nervous activity
Pavlov named the new life-science discipline of the formation and disruption of conditioned reflexes “higher nervous activity,” and in his first book on the topic (1923) he added to it the term “behavior” in parentheses. This addition indicated both Pavlov’s realization that others—notably American psychologists—saw the new discipline as the study of behavior and also his intention to convey that, while conditioned reflexes become manifest in behavior, their interpretation inheres in higher-nervous or cortical action—indeed, that they reveal this action and have no real systematic or scientific import without it. Since, however, no technique for directly probing higher-nervous or cortical action was as yet known in Pavlov’s day, he proceeded to develop a hypothetical, yet highly comprehensive, system of such action: a postulated complex interplay of neural excitation and inhibition, their irradiation, concentration, and induction, underlying all behavioral conditioned-reflex manifestations.
The Pavlovian neuroconditioning system was often called by others a conceptual (i.e., inferential) nervous system: a system based only on inferences—which is all that it originally was. Modern research, however, with its direct electroencephalographic, microelectrodic, and even biochemical probing of neural action during conditioning, seems to show that Pavlov’s inferences were for the most part correct. In any event, his original conditioning scheme, which was like the modified paradigm, provides complete information on dependent and independent variables—control and measurement of both the conditioned and the unconditioned stimuli and measurements of conditioned reflex, unconditioned reflex, and original reflex in relation to conditioned stimulus—and has in recent years become the most serviceable means of correlating direct neural action and conditioned action, thus unveiling the true physical basis of learning. This enterprise, one of the most challenging in our age, is also one in which the contact between research workers in the East and West has been very close, a fact witnessed by the Colloquium on Electroencephalography of Higher Nervous Activity in Moscow in 1958, the Macy Conferences on the Central Nervous System and Behavior in 1958, 1959, and 1960, the Montevideo Conference on Brain Mechanism and Learning in 1959, the New York Pavlovian Conference on Higher Nervous Activity in 1961, the California Conference on Brain and Behavior in 1961, and several others.
While a system of behavior based wholly on conditioned reflexes might be expected, at least superficially, to be highly mechanistic and reductionistic and not to draw a basic distinction between animal and human learning, Pavlov had, in his later years, prevented his system from having these defects. In 1927 he wrote: “Of course a word is for man as much a real conditioned stimulus as are other stimuli common to men and animals, yet at the same time it is so all-comprehending that it allows no quantitative or qualitative comparisons with conditioned stimuli in animals” ( 1960, p. 407). In 1932 Pavlov asserted that speech, and especially the kinesthetic stimuli to the cortex from the speech organs, are second signals—signals of signals. These second signals are in essence abstractions of reality and means of generalization uniquely characteristic of human higher thought ([1932a] 1941, p. 69); and, similarly, also in 1932: “In man there comes to be .. . another system of signalization, a signalization of the first system . . . a new principle of neural action is [thus] introduced” ([1932b] 1941, p. 113). This is the Pavlov “second-signal system” principle that distinguishes verbal conditioning, or language acquisition, in man from first-signal conditioning in men and animals. And it is a principle that is clearly broader than that of most American behaviorists, for whom language is either a mediator operating essentially according to the laws of the reactions that it mediates or is merely a conditioned vocal reaction.
From the very beginning Pavlov was concerned with the relation of conditioning to psychopathology (as indicated in the title of his 1903 address)—an unusual concern for that time. His interest continued, and in 1920, in Pavlov’s laboratory, N. R. Shenger-Krestovnikova demonstrated empirically how a conditioned reflex produces experimental neurosis. Thereafter Pavlov devoted a large portion of his experimental research and thought to this topic, supplementing his laboratory work with frequent visits to mental clinics. He postulated the “clash” of excitation and inhibition as the general cause of psychological disturbances and “protective inhibition” as a corrective cure. He assumed the existence of special psychopathological forms of neural action, which he termed “paradoxical,” “ultraparadoxical,” “totalinhibitory,” and “egalitarian”; he investigated them through unconditioned and conditioned behavioral manifestations. In the early 1930s K. M. Bykov, and E. Sh. Ayrapet’yants and V. L. Balakshina, began a stimulating series of experiments on interoceptive conditioning (conditioning in which direct stimulation of an internal organ is the conditioned stimulus). These experiments, which suggest promising leads to a fully objective science of psychopathology and of psychosomatics, are only now beginning to be duplicated in American laboratories. M. K. Petrova (1925) was an early pioneer in drug and sleep therapy, while a number of Pavlov’s other students made both diagnostic and therapeutic use of concepts based on interaction between the patients’ first-signal and second-signal systems.[See alsoNeurosis; Psychosomatic Illness.]
Pavlovian psychology, indeed learning psychology in general, has become so replete with tempting interpretations of psychopathology that unfortunately a good deal of uncritical writing has been published both in the United States and in the Soviet Union. Yet there is no denying the worth and soundness of the approach. In the Soviet Union it is the only one in existence, and in the United States it is gaining adherence in the face of competing approaches—notably psychoanalysis; there continue also to be many efforts to synthesize Pavlov with Freud.
As already indicated, Pavlov, Bekhterev, and the earlier work of Sechenov had in essence set forth the requisite principles for an objective and behavioral psychology a number of years before Watson launched behaviorism. However, while Watson was generally apprised of the “Pawlow method” through a short English summary in 1909, he learned of the Russians’ systematic principles only in 1914, when as he stated himself, he read the 1913 French and German translations of Bekhterev’s Objective Psychology. Watson’s 1913 article, “Psychology as a Behaviorist Views It,” in which behaviorism was first promulgated, mentions nothing of Russian research, and there is no doubt that he developed his system wholly independently. Yet Watson related himself unequivocally to the Russian enterprise afterward. When he was elected president of the American Psychological Association, the title of his presidential address was “The Place of the Conditioned Reflex in Psychology” (Watson 1916). He continued to uphold the conditioned reflex as the high hope for a true science of man and society and to produce challenging Pavlov-like and Bekhterev-like laboratory experiments. Yet Watson’s conditioned-reflex edifice—and that of early classical behaviorism in general—was in the main only programmatic and general, lacking both Pavlov’s well-knit system and its abundance of empirical material. Between 1916 and 1930 American behaviorism dealt with a single “law” of conditioning rather than with system-forming interrelated “laws,” and the number of American experiments in the area was only 16 compared to the Russians’two hundred.
The development of systems of behavior based predominantly on the conditioned reflex was begun in the United States in the early 1930s, a few years after the English translations of Pavlov’s two major books on the topic. This period marked the rise of American neobehaviorism—primarily the work of C. L. Hull, B. F. Skinner, E. R. Guthrie, and E. C. Tolman. Roughly, the two systems, Pavlovian and American, differ in that Pavlov’s is a neurobehavioral, or S-N-R (stimulus → neural process → response), system, while American neobehavioristic systems are in the main positivistic, or autochthonous-behavioral, systems: S-R (stimulus → response) or S-O-R (stimulus → organism → response), where O is a postulated matrix of mediating variables. Yet it is also true that in significant respects the difference between the Pavlovian system and the American neobehavioristic systems may well be less than the difference among the American systems themselves. Each American neobehavioristic system is broadly based on Pavlov-established conditioning laws or generalizations, plus its own superstructure.
In the United States and elsewhere outside the Soviet sphere, Pavlov has influenced all concepts of modifiable behavior or learning—what are known as the vertical dimensions of mind. However, in the Soviet Union itself his influence has also extended to mind’s horizontal dimensions—through the doctrine of types of nervous systems based on alleged genotypic individual differences in five phases of neural action (strength of excitation and of inhibition, mobility of each, and balance between the two). Roughly speaking, the doctrine posits that individual variations in unconditioned and conditioned effector reactions—in recent years also in electroencephalographic and biochemical reactions—demonstrate that the nervous systems of men and animals fall into several specific genetic types that most clearly differentiate all phases of living and behaving: from susceptibility to disease (and to ionizing radiation) and life expectancies, to work styles, motor deftness, modes of thinking, and of course temperament, personality, and emotional balance. Even variation in general intelligence—“general ability” in Russian terms—is held to be a function of the type of nervous system. To American researchers the doctrine seems hardly credible, yet it has not been tested in any significant manner outside the Soviet Union. [SeeGenetics, article onGenetics and Behavior.]
As of today one might argue with good reason and abundance of evidence that Pavlov’s neurobehavioral S-N-R system is gaining the upper hand over American pure behavioral systems—S-R andS-O-R. Recent spectacular advances in techniques of neural recording and interpretation of the information thereby obtained stress the need for integrating neural and behavioral data and relating the latter to the former. The earlier American view that the neural has no information significant to the analysis of the behavioral no longer holds. Modern psychology demands that the neural level have, and continue to have, an important role in behavioral analysis as neo-behaviorism is gradually being replaced by brain-behaviorism, which is in essence identical with Pavlovian higher nervous activity. There is also strong evidence that Pavlov was on the right track when he accorded true verbal conditioning, or language acquisition—what he called the second-signal system—a higher ontological status and when he refused to class it as merely a conditioned vocal reaction, thereby upholding the qualitative distinctness of man. Consider the clinical-neurological evidence that the human speech area is found in the associational cortex, while the mechanisms of mere vocalization—animal and human—are imbedded in the deep-lying mesencephalon. Moving away rightly from anthropomorphizing animals, psychology need not bounce to the other extreme—human zoomorphism.
In general terms Pavlov expressed a “deep, irrevocable and uneradicable conviction that this path [study of conditioned reflexes] is the path of the final triumph of the human mind over its last and uppermost problem—full knowledge of the laws and mechanisms of human nature and thus full, true, and permanent happiness . . . deliverance from present gloom and the purge of present-day shame in interhuman relations” ( 19281941, vol. 1, p. 41). He did not specifically attempt to extend his principles to any system—or indeed any analysis—of social and societal behavior, holding social science to be embryonic. But Pavlov’s students and particularly Bekhterev and his students did thus utilize conditioning concepts. However, in the middle 1930s, sociology and social psychology ceased to be independent fields of study in the Soviet Union, and the entire approach lay fallow. The two fields are now being revived and, by all tokens, so is a Marxist-Leninist and Pavlovian approach to them. In the United States the systematization of social phenomena in terms of conditioned reflexes met with considerable approval in the 1920s and early 1930s, as witnessed by the influence of Allport’s Social Psychology. But in the mid-1930s phenomenology and psychoanalysis became dominant in both sociology and social psychology, presumably because they could more readily be applied to immediate social problems. There can be no doubt, however, that ultimately, as in the case of psychopathology, societal and individual social-attitudinal changes are intimately related to learning processes and conditioning principles. Thus, a Pavlovian social psychology and sociology that is critical, comprehensive, and well systematized may well re-emerge with the ongoing rapid development of psychophysiology in the United States.
1874 O vliianii gortannykh nervov na krovoobrashchenie; O tsentrostremiternykh uskoriteliakh serdstebieniia (The Effect of the Laryngeal Nerve on Blood Circulation; The Afferent Accelerators of Tachycardia). S. Peterburgskoe Obschestvo Estestvoispytatelei, Trudy 5:lxvi-lxvii.
1878 Pavlov, Ivan P.; and Afanas’ev, M. Beiträge zur Physiologie des Pancreas. Pflüger’s Archiv für die gesamte Physiologie des Menschen und der Tiere 16, no. 2-3:173-189.
1883 Tsentrobezhnye nervy serdtsa (Efferent Nerves of the Heart). Arkhiv kliniki vnutrennykh boleznei 8: 645-719.
(1897) 1955 Lectures on the Work of the Principal Digestive Glands. Pages 83-148 in Ivan P. Pavlov, Selected Works. Moscow: Foreign Languages Publishing House. → First published as Lektsii o rabote glavnykh pishchevaritel’nykh zhelez.
(1903) 1928 Experimental Psychology and Psychopathology in Animals. Volume 1, pages 47-60 in Ivan P. Pavlov, Lectures on Conditioned Reflexes. New York: International Publishers. → First published as “Eksperimental’naiia psikhologiia i psikhopatologiia na zhivotnykh.” The translation of the extract in the text was provided by Gregory Razran.
(1904) 1928 The Psychical Secretion of the Salivary Glands. Volume 1, pages 61-75 in Ivan P. Pavlov,Lectures on Conditioned Reflexes. New York: International Publishers. → First published in French in Volume 1 of the Archives internationales de physiologie.
(1906) 1928 Scientific Study of the So-called Psychical Processes in the Higher Animals. Volume 1, pages 81-96 in Ivan P. Pavlov, Lectures on Conditioned Reflexes. New York: International Publishers. → First published in Lancet.
(1923) 1928-1941 Lectures on Conditioned Reflexes: Twenty-five Years of Objective Study of Higher Nervous Activity (Behaviour) of Animals. 2 vols. New York: International Publishers. → First published as Dvadtsatiletnii opyt ob’jektivnogo izucheniia vysshei nervnoi deiatel’nosti (povedeniia) zhivotnykh. The translation of the extracts in the text was provided by Gregory Razran.
(1927) 1960 Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex. New York: Dover. → First published as Lektsii o rabote bol’shikh polusharii golovnogo mozga.(1929-1936) 1949 Pavlovskie sredy (Pavlov’s Wednesdays). 3 vols. Moscow and Leningrad: Akademiia Nauk SSSR. -* Stenographic records of Pavlov’s informal talks.
(1931-1936) 1954-1957 Pavlovskie klinicheskie sredy (Pavlov’s Clinical Wednesdays). 3 vols. Moscow: Akademiia Nauk SSSR.
(1932a) 1941 Physiology of the Higher Nervous Activity. Volume 2, pages 60-70 in Ivan P. Pavlov, Lectures on Conditioned Reflexes. New York: International Publishers. → First published as “Fiziologiia vysshei nervnoi deiatel’nosti.”
(1932b) 1941 Essays on the Physiological Concept of the Symptomatology of Hysteria. Volume 2, pages 102116 in Ivan P. Pavlov, Lectures on Conditioned Reflexes. New York: International Publishers. → First published as Proba fiziologicheskogo ponimaniia simptomologii isterii. The translation of the extracts in the text was provided by Gregory Razran.
Polnoe sobranie trudov (Complete Works). 5 vols. Moscow and Leningrad: Akademiia Nauk SSSR, 1940-1949.
Selected Works. Edited by J. Gibbons under the supervision of K. S. Koshtoyants. Moscow: Foreign Languages Publishing House, 1955.
Akademiia Nauk Sssr, Institut Fiziologii Imeni I. P. Pavlova 1954 Bibliografiia trudov I. P. Pavlova i literature o nem (Bibliography of the Works of I. P. Pavlov and of Works About Him). Moscow and Leningrad: Akademiia Nauk SSSR.
Anokhin, P. K. 1949 Ivan Petrovich Pavlov. Moscow: Akademiia Nauk SSSR.
Babkin, B. P. 1949 Pavlov: A Biography. Univ. of Chicago Press.
Carpenter, H. C. H. 1936 Ivan Petrovich Pavlov. Royal Society of London, Obituary Notices of Fellows 2:1-24.
Hilgard, Ernest R.; and Marquis, Donald G. (1940) 1961 Hilgard and Marquis’ Conditioning and Learning. Revised by Gregory A. Kimble. 2d ed. New York: Appleton. → First published as Conditioning and Learning.
Hull, Clark L. 1943 Principles of Behavior: An Introduction to Behavior Theory. New York and London: Appleton.
Ivanov-Smolenskii, Anatolii G. (1927-1952)1954 Essays on the Patho-physiology of the Higher Nervous Activity According to I. P. Pavlov and His School.Moscow: Foreign Languages Publishing House. → First published in Russian.
Konorski, Yerzy 1948 Conditioned Reflexes and Neuron Organization. New York: Cambridge Univ. Press.
Negovskii, Vladimir A. 1954 Patofiziologiia i terapiia agonii i klinicheskoi smerti (Pathophysiology and Therapy of Agonia and Clinical Death). Moscow: Medgiz. → Published in German in 1959 by the Akademie Verlag.
Petrova, M. K. 1925 Curing Experimental Neuroses in Dogs. Arkhiv biologicheskikh nauk 35:3-16. → First published in Russian.
Razran, Gregory 1961 The Observable Unconscious and the Inferable Conscious in Current Soviet Psychophysiology: Interoceptive Conditioning, Semantic Conditioning, and the Orienting Reflex. Psychological Review 68:81-147.
Razran, Gregory 1965 Russian Physiologists’ Psychology and American Experimental Psychology. Psychological Bulletin 63, no. 1:42-64.
Sechenov, Ivan M. (1863)1935 Reflexes of the Brain. Pages 263-336 in Ivan M. Sechenov, Selected Works.Moscow: State Publishing House for Biological and Medical Literature. → First published as “Refleksi golovnogo mozga” in the journal Meditsinskii vestnik.
Skinner, B. F. 1938 The Behavior of Organisms: An Experimental Analysis. New York: Appleton.
Voprosy neuroradiologii. 1962 Akademiia Nauk SSSR, Institut Vysshei Nervnoi Deiatel’nosti, Trudy Pathophysiological Series 10. → The whole volume is devoted to the problems of neuroradiology. An English translation is available from the Office of Technical Services, U.S. Department of Commerce.
Watson, John B. 1913 Psychology as a Behaviorist Views It. Psychological Review 20:158-177.
Watson, John B. 1916 The Place of the Conditioned Reflex in Psychology. Psychological Review 23:89-116.
Pavlov, Ivan Petrovich
PAVLOV, IVAN PETROVICH
(b. Ryazan, Russia, 27 September 1849; d. Leningrad, U.S.S.R., 27 February 1936),
Pavlov was the son of a priest, Pyotr Dmitrievich Pavlov, and his wife, Varvara Ivanova. He was sent at the age of eleven to the religious school in Ryazan and , after graduating, entered the seminary of that town, where he studied the current literature on natural science, including I. M. Sechenov’s Refleksy golovnogo mozga (“Reflexes of the Brain”) and the popular works of D. I. Pisarev. He did not complete his studies there, but in 1870 entered the natural sciences section of the Faculty of physics and Mathematics at St. Petersburg University. While he was a third-year student the lectures and experimental work of E. F. Cyon decisively stimulated his interest in physiology and he carried out experimental research on the influence of the nerves on the circulation of the blood. Pavlov was awarded a gold medal for a student work on the nerves that govern the pancreas (1875), written with M. I. Afansiev.
To broaden his knowledge of physiology Pavlov entered the third-year course at the Military Medical Academy after graduating from the university in 1875. His studies were directed primarily toward theoretical medicine. In the physiology laboratory of the veterinary section of the academy, directed by K. N. Ustimovich, Pavlov conducted the research on the physiology of the circulation of the blood that brought him into contact with S. P. Botkin. He subsequently organized and headed the physiology laboratory of Botkin’s clinic (1878–1890) and conducted investigations on the physiology of circulation and of digestion. On 19 December 1879 he received the degree of doctor of medicine; in 1881 he married Serafima Vasilievna Karchevskaya.
In Botkin’s laboratory Pavlov was exposed to an atmosphere of “nervism”, which “extended the influence of the nervous system to the greatest possible amount of an organism’s activity.” 1 During this period Pavlov wrote his doctoral dissertation, on the efferent nerves of the heart, which he defended on 21 May 1883. In 1884–1886 he worked in the laboratories of Karl Ludwig in Leipzig and Rudolf Heidenhain in Breslau and, at the latter, carried out his only research in the physiology of invertebrates, published in 1885.
In 1883 Pavlov became Privatdoxent in physioglogy at the Military Medical Academy and in 1890 was appointed professor in the department of pharmacology. At the same time he became director of the physiology section of the Institute of Experimental Medicine and conducted research on the physiology of digestion that was summarized in a work published in 1897. In 1895, after the retirement of I. R. Tarkhanov, Pavlov moved to the department of physiology, which he headed until 1925. For the rest of his life his activity was concentrated at three institutes: the Institute of Physiology of the Soviet Academy of Sciences that now bears his name, the Institute of Exeriementl Medicine, and the biological station at Koltushy (now Pavlovo), near Leningrad.
Pavlov’s scientific work received worldwide recognition. In 1904 he was awarded the Nobel Prize in physiology or medicine for his research on digestion. In 1907 he was elected an academician of the Russian Academy of Sciences. In August 1935 he presided over the Fifteenth International Physiological Congress, held at Leningrad and Moscow.
Pavlov enriched physiology and the natural sciences with a new method and a new methodology. The latter derived from his general biological thought, which was directed toward the study of the whole organism under the conditions of its normal activity. For Pavlov the living organism was a complex system, the study of which—like that of any system—demanded the use of both the analytic and synthetic methods of scientific research. He considered the main problem of experimental research in physiology to be the study of reciprocal influence and reciprocal action within the organism, and the relation of the organism to its environment. In his first study of circulation he emphasized that such work was possible only by a method that allowed the systematic investigation of “those mutual relationships in which the separate constituent parts of the complex hemodynamic machine are found during its life activity.” 2 Research must be conducted under normal conditions on unprepared animal specimens.
Toward the end of the nineteenth century the essential problem of physiology was becoming the replacement of the traditional, vivisectional method with a long-term, environmental one. Such replacement was called for by the logic of the development of physiology; a vast amount of data had been accumulated by means of the vivisectional method, but it was becoming increasingly apparent that the entire organism must be studied in its natural conditions. On the limitations of vivisection Pavlov said:
Strict experiment . . . can serve the aims of physiological analysis—that is, the general clarification of the functions of a given part of an organism and its conditions—more successfully. But when, how, and to what degree the activity of the separate parts is connected . . . constitutes the content of physiological synthesis, and . . . is frequently difficult or simply impossible to deduce from the data of strict experiment, for the setting of the experiment (narcosis, curarization, operations) is inevitably linked to a certain amount of destruction of the normal processes of the organism3
Pavlov conceived the method of long-term experiment, which he introduced into the laboratory, not only as a technique of experimental research but also as a way of thinking. The continuous method inaugurated a new era in the physiology of digestion and led to new work and concepts, especially in experimental surgery and in the physiology of the brain. In his first lecture on the physiology of digestion, Pavlov said, “Science moves in spurts, depending on progress made in its methods. With each step forward in methods we rise, so to speak, to a higher step, from which a wider horizon opens to us, with subjects previously unseen.” 4 He therefore developed a synthetic physiology designed to “determine precisely the actual course of particular physiological phenomena in a whole and normal organism.” 5
The object of Pavlov’s research was both the organism as a system and any of its separate organs that fulfilled a definite function. He was not concerned with the basic principles and foundations of life, believing them to be the proper subjects of not physiological but rather physicochemical research. Characterizing his approach, he wrote:
I would prefer to remain a pure physiologist, that is, an investigator who studies the functions of separate organs, the conditions of their activity, and the synthesis of their function in the total mechanism of a part or in the whole of the organism; and I am little interested in the ultimate, deep basis for the function of an organ or of its tissues, for which primarily chemical or physical analysis is required.6
His devotion to the synthetic approach did not, however, hinder Pavlov from analytical study of the organism, “going into the depths of cellular and molecular physiology.” 7 Emphasizing the problems and goals of physiological analysis, he pointed out its role in elucidating the functional mechanisms of the organs. He distinguished four levels, or degrees, of experimental physiological research—organismic, organic, cellular, and molecular—all of which must, in the final analysis, reflect the properties of a living substance. Pavlov was well aware of the necessity of a definite, regular relationship between the holistic and analytical (or organicist and reductionist) approaches of scientific research. As a founder of organicism he clearly foresaw the advent of the cellular and molecular physiology that would greatly alter the course of organic physiology.
Pavlov stated his notion of the levels of physiological research in a speech dedicated to the memory of Heidenhain (1897), in which he said that “organic physiology . . . began its study with the middle of life; its principle, the basis of life, is in the cell.”8 He considered Heidenhain “a cellular physiologist, a representative of that physiology which must replace . . . contemporary organic physiology and which must be considered the forerunner of the last step in the science of life—the physiology of the living molecule.” 9
The greatest part of Pavlov’s research is devoted to three major areas: the physiology of the circulation of the blood (1874–1888), the physiology of digestion (1879–1897), and the physiology of the brain and of higher nervous activity (1902–1936). His earliest research in the physiology of circulation was devoted to the mechanisms that regulate blood pressure. He described the role of the nerve mechanism in the adaptive activity of the blood vessels, specifying the role of the vagus nerve as a regulator of blood pressure. In his doctoral dissertation he showed that cardiac function is governed by four nerves which respectively inhibit, accelerate, weaken, and intensify it. (Prior to his work and that of Gaskell it was believed that the influence of the nerves on the heart was limited to changing its rhythm.) Pavlov’s research in this area culminated with the publication in 1888 of his work on the intensifying nerve, in which he proposed that its influence be understood as trophic. In the 1920’s he returned to trophic innervation, the idea upon which L. A. Orbeli had based his theory of the adaptive trophic role of the sympathetic nervous system.
Pavlov’s research on the physiology of digestion (1897, 1906, 1911) required him to devise new techniques and thereby marked a turning point in his work. His method for studying the action of the digestive organs involved surgical intervention on the entire digestive tract, performed under conditions of strict asepsis and antisepsis, which allowed him to observe the normal activity of a particular digestive gland in a healthy animal. (A mastery of surgery was, for Pavlov, as necessary to the physiologist as a knowledge of physical and chemical methods of research.) His surgical procedures included the formation of various types of fistulas from the salivary glands, the stomach, and the pancreas to the body surface, known as esophagotomy; “imaginary feeding,” carried out with E. O. Shumova-Simanovskaya (1889); the operation on the small ventricle of the stomach, formed with P. P. Khizhin (1894); and the severing of two branches of the vagus nerve and the application of the fistula of Eck (1892). He was thus enabled to investigate, more or less directly, the mechanisms governing the salivary glands, stomach, pancreas, kidneys, and intestines.
Pavlov’s experiments proceeded from contemporary ideas about the neural and humoral regulation of the digestive process and of its consequences in various parts of the digestive tract. He showed that there is a close connection between the properties of salivary secretion and the kind of food consumed (the Pavlovian curves of salivary secretion). He elucidated the role of enzymes in digestion and, with N. P. Shepovalnikov, discovered enterokinase—which he called “the enzyme of enzymes”in the intestinal secretion (1894). His theoretical conclusions were of broad biological significance. His theory of specific irritability was of particular importance—in showing that the concept of general irritability is scientifically untenable, he demonstrated specific irritability in various parts of the digestive tract. The Pavlovian theory of digestion was of great value in the clinical pathology of the stomach and intestines.
Following his work on the physiology of digestion, Pavlov turned to the physiology of behavior. By the beginning of the twentieth century many physiologists, zoologists, and psychologists had already undertaken experiments to study the function of the brain, but had assembled only fragmentary data. Pavlov drew upon Darwin’s theory of evolution—which stressed psychological as well as physiological continuity—and Sechenov’s reflexology to create his own theory of behavior. Pavlov thus described the genesis of his behaviorism: “The time is ripe for the transition to experimental analysis of the subject from the objective, external side, as in all the other natural sciences. This transition has made possible the recently born [study of] comparative physiology, which itself arose as one of the results of the influence of evolutionary theory.”10
Pavlov investigated the activity of the cortex and the cerebral hemispheres, basing his work on fundamental facts, concepts, and terminology of the physiology of the nervous system. He chose to approach these areas through studying the salivary glands, which had attracted his attention because of their modest role in the organism and because their activity could be subjected to strict quantitative measurement. He had, moreover, already encountered the phenomenon of “psychic” salivation in the course of his investigations on the physiology of digestion, and wished to study it further. Subjective psychology held that saliva flowed because the dog wished to received a choice bit of meat, but Pavlov, ’an experimenter from head to foot,” rejected this method as fallacious and chose to pursue the investigation objectively.
Pavlov could not help but see the “psychic” stimulation of the salivary glands as a phenomenon analogous to the normal digestive reflex. Both digestion and salivation were reflexive; only the external agents that evoked the reflexes were different. The digestive reflex was triggered by the essential mechanical and chemical properties of the food; the salivary by nonphysiological “signals” including the form and odor of the food. Using the concept of the reflex as an elementary response of the organism to external stimulus, Pavlov termed the normal digestive reaction an unconditioned reflex, and the activity of the salivary glands, stimulated by various environmental agents, a conditioned reflex.
Pavlov described the formation of the conditioned reflex, showing it to be based, like the unconditioned reflex, on the innate activity of the organism. He demonstrated that any environmental factor can enter into a temporary relation with the natural activity of the organism through combination with the unconditioned reflex. He noted that the chief characteristics of conditioned reflexes are that they are developed throughout the life of an organism (and are therefore extraordinarily subject to change, depending on the environment) and that they are provoked by stimuli that act as signals. Taken together, these qualities ensure the organism a completely individual adaptive activity. Pavlov saw in the conditioned reflex a mechanism through which the ameliorative potentialities of the organism are increased.
Pavlov made his first public statement on the conditioned reflex in 1903, in a paper presented to the Fourteenth International Medical Congress in Madrid. He expanded upon the subject three years later, when he wrote that
. . . with the general biological point of view before us we find in this conditioned reflex an improved adaptive mechanism or, in other words, a more precise mechanism for counterbalance with the environment. The organism reacts with natural phenomena that are vital to it in the most sensible and most precautionary way, since all other, even the smallest phenomena . . ., although accompanying the first only temporarily, present themselves as signals of the first—signals of the stimulus. The subtlety of the procedure makes itself known in the formation of the conditioned reflex as well as in its suppression, when it ceases to be a correct signal. Here, we must think, lies one of the main mechanisms of progress in the more finely differentiated nervous system.… The concept of the conditioned stimulus must be seen as the fruit of the previous work of biologists.… 11
Pavlov found in the conditioned reflex a mechanism of individual adaptation which, he held, exists throughout the entire animal world. “A temporary nervous connection is a universal physiological phenomenon in the animal world and exists in us ourselves.” 12
Pavlov localized conditioned-reflex activity in the cerebral hemispheres of the brain, demonstrating that the center for such activity is to be found in the cortex, among the cortical agents of innate reflexes. Pavlov considered the possibility that subcortical formations may be responsible for the placement of the conditioned-reflex centers, but did not offer any direct evidence for this. He showed that with the formation of conditioned reflexes in the functional state of nerve centers displacements occur in the form of increases in irritability. The cells of the higher sections of the central nervous system, and their branches, he suggested, must therefore undergo definite subtle structural and physicochemical changes. “The lockingin, the formation of new connections", he wrote, “we relate to the function of the separating membrane, if it exists, or simply to the fine branching between neurons [that is], between the separate nerve cells.” 13 Pavolov’s hypothesis has been verified by more recent neurophysiological data, which have demonstrated the plastic character of the changes in the synactial apparatus as a result of excitation. Through work on the conditioned reflex investigators were able to establish that the activity of the cerebral hemispheres is based on the processes of excitation and inhibition. Further experiments, designed to elucidate the dynamics and mutual relationships of these processes, revealed a definite regularity in their development.
An important concomitant of Pavlov’s experimental work was his creation of experimental neuroses, which arose when contradictory stimuli were offered the subject. Such neuroses may serve as a rough model for functional disease of the human nervous system; Pavlov and his co-workers attributed them to the disturbance of balance between the cortical processes of excitation and inhibition. In 1924, in Pavlov’s laboratory, I. P. Razenkov, investigating the induced conflict of basic nerve processes in the activity of the cerebral cortex, observed the same phase states as N. E. Vvedensky had observed in the nerve fiber. It was shown that disturbance of cortical activity passed through four stages: inhibiting, characterized by the absence of all reflexes; paradoxical, in which strong stimuli produce little or no effect, while weak stimuli induce greater effects; equalizing, in which all conditioned stimuli, regardless of their intensity, produce the same effect; and intermediate to the norm, in which stimuli of average intensity produce the greatest effect, and strong or weak conditioned stimuli induce little or no effect. Pavlov applied Razenkov’s work, which provided the first description of phase states of the central nervous system, toward understanding the nature of human psychic illness. From 1918 on, he regularly visited a psychiatric clinic in Udelnaya, near Leningrad, to study the patients.
A. G. Ivanov-Smolensky, V. V. Rikman, I. S. Rosenthal, I. O. Narbutovich, and L. N. Fedorov were active in the creation of the theory of experimental neuroses. Pavlov’s student M. K. Petrova was able to induce deliberately various specific neuroses in animals and subsequently to suppress them. This study of experimental neuroses was closely related to the development of the theory of types of behavior. In 1909 Pavlov reported his pioneering work on behavior to the Society of Russian Physicians in St. Petersburg; his paper Dalneyshie shagi obektivnogo analiza slozhnonervnykh yavleny (“Further Steps in the Objective Analysis of Complex Nerve Phenomena”) discussed carefully conditioned, “weak-nerved” dogs, in which it was difficult to induce inhibition.
In addition to studying animal behavior and the accumulating experimental material, Pavlov and his co-workers made the first attempt to provide a scientific basis for the ancient Hippocratic classification of temperaments. They established the existence of four basic types of behavior, which they classified according to the strength, mobility, and constancy of the basic nerve processes.
During the 1920’s two ramifications emerged from Pavlov’s basic theory: the study of comparative physiology of behavior and the theory of human behavior. Pavlov had experimented on dogs, mice, and monkeys’ his students expanded the range of animal subjects, E. M. Kreps working with Ascidia, Y. P. Frolov with fish, N. A. Popov and B. I. Bayandurov with doves, P. M. Nikiforovsky and E. A. Asratyan with amphibians and reptiles, and G. A. Vasiliev and A. N. Promptov with birds. In the next decade Pavlov himself took up the idea of the genetic study of behavior; a biological station was established for this purpose at Koltushy, near Leningrad. On the basis of comparative physiological data an attempt was made, chiefly by Pavlov’s student L. A. Orbeli, to create an evolutionary physiology of behavior.
Pavlov attributed decisive importance to the signals that characterize conditioned-reflex activity. He assumed the existence of two signal systems, of which one, the primary system, is found in both animals and man, whereas the secondary system is peculiar to man, and it is this system that makes possible the distinctively human activities of abstract thought and speech. In recent years he has come to be regarded as a mechanist who saw complex behavior as the sum of individual conditioned reflexes. This is a profound error, since in Pavlov’s view the brain, through its capacity for subtle analysis and complex synthesis, integrates a vast range of conditioned reflexes into coherent behavior corresponding to the specific circumstances and needs of the organism. If in the early stages of his work Pavlov and his students were chiefly concerned with the study of elementary conditioned reflexes, they later turned to purposeful study of the more complex forms.
A distinguished scientific administrator, Pavlov created a large research school that, at various times, employed about 300 physiologists and physicians. He also organized a number of major research centers, including the physiological section of the Institute of Experimental Medicine, the Institute of Physiology of the Soviet Academy of Sciences, and the biological station at Koltushy. With Pavlov’s active cooperation the Russian Physiological Society (now the I. P. Pavlov All-Union Physiological Society) was organized in 1917. He was an active member of the Society of Russian Physicians in St. Petersburg, and his services were highly valued by the Soviet government.
1. I. P. Pavlov, Polnoe sobranie sochineny (“Complete Collected Works”), 2nd ed. (Moscow–Leningard, 1951–1952), I, 197.
2.Ibid., I, 82.
3.Ibid., VI, 321.
4.Ibid., II, bk. 2, p. 22.
6. A. F. Samoylov, Izbrannye trudy (“Selected Works”), V. V. Parin, ed. (Moscow, 1967), 301.
7. I. P. Pavlov, Polnoe sobranie sochineny, I, 574.
8.Ibid., VI, 104.
10.Ibid., IV, 19.
11.Ibid., II, bk. 1, p. 71.
12.Ibid., II, bk. 2, p. 182.
13.Ibid., II, bk. 2, p. 61.
I. Original Works. Pavlov’s writings were collected as Polnoe sobranie trudov (“Complete Collected Works”), 5 vols. (Moscow, 1940–1949). The 2nd ed. is Polnoe sobranie sochineny (“Complete Collected Works”), 6 vols. (Moscow–Leningard, 1951–1952). There is a German trans. of this ed., Säamtliche Werke, L. Pickenhain, ed., 6 vols. (Berlin, 1953–1956).
Works referred to in the text are O nervakh, zavedyvayushchikh rabotoy v podzheludochnoy zheleze (“On the Nerves That Govern the Pancreas”; 1875), written with M. I. Afanasiev’ O isentrobezhnykh nervakh serdtsa (“On the Efferent Nerves of the Heart”; St. Petersburg, 1883), his doctoral diss.; “Kak bezzubka raskryvaet svoi stvorki” (“How the Anodonta Opens Its Valves”; Polnoe sobranie sochineny, 1 , 466–493, also in Pflugers Archiv, 37 , 6–31); Lektsii o rabote glavnykh pishchevaritelnykh zhelez (“Lectures on the Function of the Main Food-Digesting Glands”; 1897); Eksperimentalnaya psikhologia i psikhopatologia na zhivotnykh (“Experimental Psychology and Psychopathology in Animals”; 1903), his first public statement on the conditioned reflex; “Vneshnyaya rabota pishchevaritelnykh zhelez i ee mekhanizm” (“The External Function of the Digestive Glands and Its Mechanism”), in W. Nagel, ed., Handbuch der Physiologie des Menschen, Ii (Brunswick, 1907), 666–743; “Operativnaya metodika izuchenia pishchevaritelnykh zhelez” (“An Operative Method of Studying the Digestive Glands”; in Tigerstedt’s Handbuch der physiologischen Methodik, Band II, IH, Leipzig, 1911); Dvadtsatiletny opyt obektivnogo izuchenia uysshey nervnoy deyatelnosti (povedenia) zhivotnykh (“Twenty Years of Experiments in the Objective Study of Higher Nervous Activity [Behavior] of Animals”; Moscow–Petrograd, 1923); and Lektsii o rabote bolshikh polushary golovnogo mozga (“Lectures on the Function of the Cerebral Hemispheres”; Moscow, 1927), Pavlov edited vols. 1–6 (1924–1936) of Trudy fiziologicheskikh laboratorii imeni I. P. Pavlova.
Important English translations of his works include The Work of the Digestive Glands, W. H. Thompson, trans. (London, 1902; 2nd ed., 1910); Conditioned Reflexes, G. V. Anrep, trans. and ed. (London, 1927; repr. New York, 1960), a trans. of the 1923 work cited above; and Lectures on Conditioned Reflexes, W. H. Gantt, trans. (New York, 1928).
II. Secondary Literature. On Pavlov’s life and work, see P. K. Anokhin, Ivan Petrovich Pavlov Zhizn, deyatelnost i nauchnaya shkola (“. . . Life, Work, and Scientific School”; Moscow-Leningard, 1949); E. A. Asraty; Ivan Petrovitch Pavlov, Work (Moscow, 1974), in English B. P. Babkin, Pavlov (Chicago, 1949); Y. P. Frolov, Pavlov and His School (London, 1937), written by a student of Pavlov; and E. M. Kreps, ed., I. P. Pavlov v vospominaniakh sovremennikov (“Pavlov Recalled by His Contemporaries”; Leningard, 1967).
N. A. Grigorian
Pavlov, Ivan Petrovich
PAVLOV, IVAN PETROVICH
(b. Ryazan, Russia, 27 September 1849; d. Leningrad, U.S.S.R., 27 February 1936), physiology, psychology. For the original article on Pavlov see DSB, vol. 10.
Near the end of his long productive career, Pavlov mused that the life’s work of a scientist consisted in the writing of “only a single book,” by which he meant the development of a single set of basic themes through a consistent set of scientific practices. That was certainly true of Pavlov himself: an unvarying scientific style united his Nobel Prize-winning research on digestion with his renowned investigations of higher nervous activity. This research prospered under czarism and then gained fulsome levels of support from Russia’s Communist leaders despite Pavlov’s frequent bitter criticism of their policies.
Research Style Pavlov’s scientific style represented a layering of experiences and attitudes from his youth in Ryazan in the 1860s, his studies at St. Petersburg University in the 1870s, his stay in the laboratories of Rudolf Heidenhain and Carl Ludwig in the 1880s, and the institutional circumstances from the 1890s through the 1930s that allowed him to refine and practice his conception of good science. That conception and those practices remained remarkably consistent during more than fifty years of scientific work.
As a teenage seminarian Pavlov fell under the spell of Russia’s “men of the sixties” and their vision of curing Russia’s backwardness through the ideological clarity and technological progress resulting from the practice and popularization of materialist natural science. As a student at St. Petersburg University (1870–1875), however, his beloved mentor in physiology was the politically conservative Ilya Tsion. Tsion taught him a Bernardian style of physiology and the surgical skills to practice it. According to this style, the physiologist sought determined, purposive patterns in the activity of organ systems (which were “high” enough to capture the vital qualities the physiologist studied, while “low” enough to establish the determined relations governing their activity). In one respect, Pavlov would go Claude Bernard one better: From the 1880s onward, he insisted upon studying intact, “normal” organisms in order to examine physiological processes in an undistorted state. As a visitor in Ludwig’s lab in Leipzig and Heidenhain’s in Breslau (1884–1886), Pavlov appreciated Ludwig’s insistence upon quantitative results but preferred Heidenhain’s more supple and specifically physiological interpretive style. These various experiences framed what Pavlov would call “physiological thinking.” For him, good physiology must both study the intact normal organism (in which, Pavlov knew, uncontrolled variables always abounded) and also establish the precise, determined, repeatable results that characterized any true science.
Pavlov’s tenure with Heidenhain and Ludwig also impressed upon Pavlov the advantages of the larger lab enterprise that was beginning to replace the Bernardian-style single investigator and led him to reflect upon the spiritual and organizational attributes of a scientific manager. He was able to put these into effect only in 1890–1891 when, at age forty-one, a set of unlikely circumstances transformed him from a floundering, part-time lecturer and lab assistant into the master of Russia’s largest physiological laboratory at Prince Ol’denburgskii’s new Imperial Institute of Experimental Medicine in St. Petersburg. Here Pavlov coordinated the labors of about twelve co-workers annually, the great majority of whom were physicians untrained in physiology and seeking a quick doctorate. During the last decade of czarist rule, women entered this laboratory work force. Pavlov’s lab featured an authoritarian structure and cooperative ethos that allowed him to use co-workers as extensions of his sensory reach while enabling him constantly to monitor the work process, to control the interpretive moments in experiments, and to incorporate results into his developing ideas. His laboratory enterprise expanded in pre-revolutionary years to include also smaller labs at St. Petersburg’s Military Medical Academy and Academy of Sciences.
Scientific Research In the years 1891–1903, Pavlov concentrated on the studies of the digestive system that were systematized in his Lectures on the Work of the Main Gastric Glands (1897) and won him a Nobel Prize in Physiology or Medicine (1904). In this research, Pavlov’s “physiological thinking” was embodied in the “chronic experiment,” and his analysis of data was structured by his metaphor of the digestive system as a precise and purposive “chemical factory.” For the chronic experiment, experimental dogs were prepared surgically with an operation designed to give the experimenter access to a digestive gland. Experiments began only after the dog had recovered and regained a “normal” state. These operations included the esophagotomy, which separated the cavities of the mouth and stomach, allowing Pavlov to use sham-feeding experiments to demonstrate the centrality of a psychic actor, appetite, in the first phase of digestive secretion. To study the second, nervous-chemical phase of digestion, he developed an innervated version of Heidenhain’s “isolated stomach.” In Pavlov’s isolated sac, the main stomach remained continuous with the digestive tract, but a smaller pouch, isolated from food by a mucous membrane, maintained its nervous connections to the larger stomach. For Pavlov, as a nervist, the innervation of the isolated sac assured that its glandular reactions would mirror those in the main stomach. Inserting a fistula in this small stomach, Pavlov and his co-workers measured the quantity and quality of its glandular secretions, which Pavlov analyzed in his “characteristic secretory curves.” For Pavlov, these curves reflected the precise and purposive action of the glands as they processed different foods.
Pavlov constantly sought to link his laboratory findings to clinical concerns. The results of his digestive research ranged from specific discoveries (for example, the central role of the vagus nerve) to clinical innovations (for example, the use of the “natural gastric juice” drawn from lab animals as a scientific remedy for dyspepsia) to an all-encompassing nervist analysis of the factorylike functioning of the digestive glands.
By the time Pavlov received the Nobel Prize for this research, he was moving his lab group on to the use of conditional reflexes as a method to investigate the principal actor in the first phase of digestion, the psyche. The dogs used in chronic experiments often lived for years in the lab, and experimenters were familiar with their differing moods and personalities (which Pavlov often invoked to explain discrepancies in experimental results). Now that psyche itself, under the rubric of “higher nervous activity,” became Pavlov’s investigative target. Here, too, Pavlov relied on chronic experiments with intact dogs (usually fitted with a salivary fistula) to produce quantitative data (saliva drops); and here, too, he attempted to reason from that data to the determined physiological processes that had produced them.
Like Darwin, Pavlov assumed that dogs were conscious beings with thoughts and emotions, and unlike the behaviorists of his day, he considered the explanation of such subjective states the proper province of science. The iconic image of a Pavlovian dog salivating to the sound of the buzzer captures not the end point, but rather the point of departure for Pavlov’s investigations. Lay observers, animal trainers, and physiologists had long noticed that a hungry dog salivates at the sight of food, its food bowl, or the person who usually fed it. Pavlov always viewed his particular achievement as the transformation of this familiar “psychic secretion” into a reliable laboratory phenomenon and its use as a method for understanding the unseen processes in the brain that produce thoughts, emotions, and behaviors.
His research strategy from 1903 to 1936 involved three basic, and constantly interacting, steps: (1) establish experimentally the fully determined regularities in the salivation elicited by highly varied experiments on conditional reflexes; (2) use these regularities to develop a model of the unseen processes in the brain that might have produced them; and (3) use this model to explain the behavior, affect and personality of his experimental animals.
From 1903 to 1936 Pavlov employed conditional reflex experiments in elegant analyses of the sensory abilities of the dog (for example, its ability to distinguish between colors, shapes, and time intervals) and to develop a schematic map of higher nervous processes that featured the interplay of the two basic processes of inhibition and excitation and their movement and complex interaction in the cerebral cortex. His determination that a balance between excitation and inhibition was necessary to a dog’s ability to perceive accurately and respond to its environment—and his awareness that identical experiments produced varying results in different dogs—encouraged his interest in “nervous types” among dogs, people, and peoples. In keeping with his lifelong determination to link laboratory studies to the clinic, research on nervous types generated a line of investigation on “the pathology and therapeutics of higher nervous activity”—involving the creation and treatment of “experimental neurosis” in lab animals—and then on psychiatry.
By the late 1920s Pavlov concluded that the explanation of a dog’s performance in experiments required not just an understanding of its inborn nervous type, but also of the influence upon its nervous system of upbringing, training, and the “social exciter.” In the late 1920s and 1930s these became research subjects at his rural science village in Koltushi, some twelve miles (twenty kilometers) outside of Leningrad. At this Institute of the Experimental Genetics of Higher Nervous Activity, Pavlov and his co-workers also studied the chimpanzees Roza and Rafael and launched an attempt to develop an “improved nervous type” through selective breeding. Long concerned about the weaknesses of the “Russian type”—which he believed to be badly imbalanced toward excitation— Pavlov announced that this eugenics project was “for the use and glory, most of all, of my homeland.”
Political and Cultural Figure The construction of Koltushi—which began in earnest as an eightieth birthday present from the Communist Party—represented the culmination of a long process of struggle and accommodation between Pavlov and the Bolsheviks. Pavlov’s political views had always revolved around his scientism and contradictory patriotism (on the one hand, concern about the “Russian type,” on the other, a deep cultural pride and identification with the power and prestige of the Russian state). Before 1917 he had supported Russia’s gradual evolution toward a constitutional monarchy and stood unsuccessfully for the Duma in 1907 as a candidate of the center-right Octobrist Party. Appalled by the Bolshevik seizure of power, he seriously considered emigration before reaching an uneasy accommodation with the Communist Party in 1921. He received virtual carte blanche from the state, and his scientific enterprise expanded far beyond that of czarist days; in his final years he was coordinating the scientific work of about fifty co-workers annually. With the booming support for science of the Soviet state, the new
generation of co-workers in his labs were no longer the mere “skilled hands” of czarist days, but rather professional physiologists who often remained in the lab long enough to contribute research ideas of their own.
Pavlov excoriated the Communist Party throughout the 1920s, when he became a rare public voice of dissent. Yet he enjoyed good working relations with Communists in his lab and the state apparatus. By the 1930s he had been successfully cultivated by several national Communist leaders, most notably Nikolai Bukharin. Pavlov continued to denounce the regime’s incompetence, dishonesty, suppression of dissent, ideological dogmatism, and persecution of religion. (This latter position encouraged the erroneous rumor that he was himself a believer.) Yet he also praised Soviet achievements, most importantly the support for and popularization of science. As a lifelong adherent of scientism, Pavlov believed the development of Russian science would eventually moderate and improve the regime itself. In addition, the Nazi seizure of power encouraged him to close ranks behind his country’s leadership. In 1935 he rewarded the Bolsheviks by using his influence to bring the Fifteenth International Congress of Physiologists to Russia and by toasting his country’s “great experimenters” before the audience there. At that meeting and elsewhere he used his access to high state officials to save co-workers and acquaintances from the gulag.
Merely famous as a Nobelist in the early twentieth century, Pavlov achieved iconic status in the late 1920s as an international symbol of the power of experimental biology to understand and control human nature. Yet he was disappointed by the failure of scientists, particularly in the west, to adopt his approach and methodologies.
Western studies of Pavlov were long hampered by Soviet state control of Pavlov’s rich archival legacy and by the language barrier. The standard English translations of his works do not capture the metaphorical resonance of his language and are sometimes misleading—for example, in their rendering of the Russian uslovnyi refleks as “conditioned reflex” rather than “conditional reflex.”
Furthermore, because Pavlov’s reports and publications synthesized his co-workers’ experiments, his reasoning can be understood only by reading his works (and lab notebooks) alongside their dissertations and articles. In Russia, Pavlov scholarship was initially dominated by his admiring disciples and then, until the fall of Communism, by physiologist-historians constrained by the official image of this national hero and trained in the combination of positivism and wooden Whig Marxism (teleological interpretations of the past from the perspective of the present) that dominated the history of science during the Soviet era.
Joravsky, David. Russian Psychology: A Critical History. Oxford; Cambridge, MA: Basil Blackwell, 1989.
Nozdrachev, Aleksandr Danilovich, Poliakov, E. L., Kosmachevskaia, E. A., et al., eds. I. P. Pavlov: Pervyi Nobelevskii Laureat Rossii. 3 vols. St. Petersburg, Russia: Gumnistika, 2004.
Rütting, Torsten. Pavlov und der Neue Mensch: Diskuse uber Disziplinierung in Sowjetrussland. Munich, Germany: R. Oldenbourg, 2002.
Todes, Daniel. “Pavlov and the Bolsheviks.” History and Philosophy of the Life Sciences 17, no. 3 (1995):379–418.
———. Pavlov’s Physiology Factory: Experiment, Interpretation, Laboratory Enterprise. Baltimore, MD: Johns Hopkins University Press, 2002.
Daniel P. Todes
Ivan Petrovich Pavlov
Ivan Petrovich Pavlov
The Russian physiologist Ivan Petrovich Pavlov (1849-1936) pioneered in the study of circulation, digestion, and conditioned reflexes. He believed that he clearly established the physiological nature of psychological phenomena.
Ivan Pavlov was born in Ryazan on Sept. 26, 1849, the son of a poor parish priest, from whom Pavlov acquired a lifelong love for physical labor and for learning. At the age of 9 or 10, Pavlov suffered from a fall which affected his general health and delayed his formal education. When he was 11, he entered the second grade of the church school at Ryazan. In 1864 he went to the Theological Seminary of Ryazan, studying religion, classical languages, and philosophy and developing an interest in science.
Making of a Physiologist
In 1870 Pavlov gained admission to the University of St. Petersburg (Leningrad), electing animal physiology as his major field and chemistry as his minor. There he studied inorganic chemistry under Dmitrii Mendeleev and organic chemistry under Aleksandr Butlerov, but the deepest impression was made by the lectures and the skilled experimental techniques of Ilya Tsion. It was in Tsion's laboratory that Pavlov was exposed to scientific investigations, resulting in his paper "On the Nerves Controlling the Pancreatic Gland."
After graduating, Pavlov entered the third course of the Medico-Chirurgical Academy (renamed in 1881 the Military Medical Academy), working as a laboratory assistant (1876-1878). In 1877 he published his first work, Experimental Data Concerning the Accommodating Mechanism of the Blood Vessels, dealing with the reflex regulation of the circulation of blood. Two years later he completed his course at the academy, and on the basis of a competitive examination he was awarded a scholarship for postgraduate study at the academy.
Pavlov spent the next decade in Sergei Botkins laboratory at the academy. In 1883 Pavlov completed his thesis, The Centrifugal Nerves of the Heart, and received the degree of doctor of medicine. The following year he was appointed lecturer in physiology at the academy, won the Wylie fellowship, and then spent the next 2 years in Germany. During the 1880s Pavlov perfected his experimental techniques which made possible his later important discoveries.
In 1881 Pavlov married Serafima Karchevskaia, a woman with profound spiritual feeling, a deep love for literature, and strong affection for her husband. In 1890 he was appointed to the vacant chair of pharmacology at the academy, and a year later he assumed the directorship of the department of physiology of the Institute of Experimental Medicine. Five years later he accepted the chair of physiology at the academy, which he held until 1925. For the next 45 years Pavlov pursued his studies on the digestive glands and conditioned reflexes.
During the first phase of his scientific activity (1874-1888), Pavlov developed operative-surgical techniques that enabled him to perform experiments on unanesthetized animals without inflicting much pain. He studied the circulatory system, particularly the oscillation of blood pressure under various controlled conditions and the regulation of cardiac activity. He noted that the blood pressure of his dogs hardly varied despite the feeding of dry food or excessive amounts of meat broth. In his examination of cardiac activity he was able to observe the special nerve fibers that controlled the rhythm and the strength of the heartbeat. His theory was that the heart is regulated by four specific nerve fibers; it is now generally accepted that the vagus and sympathetic nerves produce the effects on the heart that Pavlov noticed.
In the course of his second phase of scientific work (1888-1902), Pavlov concentrated on the nerves directing the digestive glands and the functions of the alimentary canal under normal conditions. He discovered the secretory nerves of the pancreas in 1888 and the following year the nerves controlling the secretory activity of the gastric glands. Pavlov and his pupils also produced a considerable amount of accurate data on the workings of the gastrointestinal tract, which served as a basis for Pavlov's Lectures on the Work of the Principal Digestive Glands (published in Russia in 1897). For this work Pavlov received in 1904 the Nobel Prize in physiology or medicine.
The final phase of Pavlov's scientific career (1902-1936) was primarily concerned with ascertaining the functions of the cerebral cortex by means of conditioned reflexes. Prior to 1900, Pavlov observed that his dogs would secrete saliva and gastric juices before the meat was actually given to them. The sight, odor, or even the footsteps of the attendant were sufficient to trigger the flow of saliva. Pavlov realized that the dogs were responding to activity associated with their feeding, and in 1901 he termed such a response a "conditioned reflex," which was acquired, or learned, as opposed to the unconditioned, or inherited, reflex. He faced a dilemma: could he embark on the study of conditioned reflexes by applying physiological methods to what was generally viewed as psychic phenomena? He opted to follow Ivan Sechenov, who considered that, in theory, psychic phenomena are essentially reflexes and therefore subject to physiological analysis.
The important lectures, papers, and speeches of Pavlov dealing with conditioned reflexes and the cerebral cortex are presented in Twenty Years of Objective Study of the Higher Nervous Activity (Behavior) of Animals: Conditioned Reflexes (1923) and Lectures on the Work of the Cerebral Hemispheres (1927). He not only concerned himself with the formation of conditioned responses but noted that they were subject to various kinds of manipulation. He discovered that conditioned responses can be extinguished—at least temporarily—if not reinforced; that one conditioned stimulus can replace another and yet produce identical conditioned responses; and that there are several orders of conditioning. In time Pavlov developed a purely physiological theory of cortical excitation and inhibition which considered, among other things, the process of sleep identical with internal inhibition. However magnificent his experiments were in revealing the responses of animals to conditioning stimuli, he encountered difficulty in experimentally proving his assertion that conditioned responses are due to temporary neuronal connections in the cortex.
In 1918 Pavlov had an opportunity to study several cases of mental illness and thought that a physiological approach to psychiatric phenomena might prove useful. He noted that he could induce "experimental neuroses" in animals by overstraining the excitatory process or the inhibitory process, or by quickly alternating excitation and inhibition. Pavlov then drew an analogy between the functional disorders in animals with those observed in humans. In examining the catatonic manifestations of schizophrenia, he characterized this psychopathological state as actually being "chronic hypnosis"—chiefly as a consequence of weak cortical cells—which functions as a protective mechanism, preserving the nerve cells from further weakening or destruction.
In Pavlov's last scientific article, "The Conditioned Reflex" (1934), written for the Great Medical Encyclopedia, he discussed his theory of the two signaling systems which differentiated the animal nervous system from that of man. The first signaling system, possessed both by humans and animals, receives stimulations and impressions of the external world through sense organs. The second signaling system in man deals with the signals of the first system, involving words, thoughts, abstractions, and generalizations. Conditioned reflexes play a significant role in both signal systems. Pavlov declared that "the conditioned reflex has become the central phenomenon in physiology"; he saw in the conditioned reflex the principal mechanism of adaptation to the environment by the living organism.
Philosophy and Outlook
Pavlov's endeavor to give the conditioned reflex widest application in animal and human behavior tended to color his philosophical view of psychology. Although he did not go so far as to deny psychology the right to exist, in his own work and in his demands upon his collaborators he insisted that the language of physiology be employed exclusively to describe psychic activity. Ultimately he envisioned a time when psychology would be completely subsumed into physiology. Respecting the Cartesian duality of mind and matter, Pavlov saw no need for it inasmuch as he believed all mental processes can be explained physiologically.
Politically, most of his life Pavlov was opposed to the extremist positions of the right and left. He did not welcome the Russian February Revolution of 1917 with any enthusiasm. As for the Bolshevik program for creating a Communist society, Pavlov publically stated, "If that which the Bolsheviks are doing with Russia is an experiment, for such an experiment I should regret giving even a frog." Despite his early hostility to the Communist regime, in 1921 a decree of the Soviet of People's Commissars, signed by Lenin himself, assured Pavlov of continuing support for his scientific work and special privileges. Undoubtedly, Soviet authorities viewed Pavlov's approach to psychology as confirmation of Marxist materialism as well as a method of restructuring society. By 1935 Pavlov became reconciled to the Soviet Communist system, declaring that the "government, too, is an experimenter but in an immeasurably higher category."
Pavlov became seriously ill in 1935 but recovered sufficiently to participate at the Fifteenth International Physiological Congress, and later he attended the Neurological Congress at London. On Feb. 27, 1936, he died.
Still the finest biographical study of Pavlov is the one produced by his senior surviving student, Boris P. Babkin, Pavlov: A Biography (1949). Also useful are Ezras A. Asratian, I. P. Pavlov: His Life and Work (1953), and Harry K. Wells, Ivan P. Pavlov: Toward a Scientific Psychology and Psychiatry (1956). For the influence of Pavlov on Soviet psychology see Raymond A. Bauer, The New Man in Soviet Psychology (1952), and A Handbook of Contemporary Soviet Psychology, edited by Michael Cole and Irving Maltzman (1969). An early history of Russian physiology is in Alexander S. Vucinich, Science in Russian Culture: A History to 1860 (1963). □
Ivan Petrovich Pavlov
Ivan Petrovich Pavlov
Ivan Petrovich Pavlov was born in Ryazan, Russia. After attending a local theological seminary, Pavlov traveled to the University of St. Petersburg, where he undertook the study of chemistry and physiology. Pavlov earned his medical degree from the Imperial Medical Academy in 1879. A year later, Pavlov assumed a professorship at the academy, a post he was to maintain throughout the tumultuous 1917 Russian Revolution.
Pavlov began his postgraduate work with studies on the mechanistic physiology of the circulatory system. Subsequently, Pavlov's work centered on nervous control of the heart. Eventually, Pavlov moved on to studies of the digestive system, and his efforts resulted in the publication of a well-received 1897 work titled Lectures on the Work of the Digestive Glands.
Although Pavlov's work on digestive secretions earned a 1904 Nobel Prize for physiology or medicine, Pavlov is best known for his work with conditioned reflexes. Pavlov's classic experiment involved training a hungry dog to salivate at the sounding of a bell, rather than at the food itself. Pavlovian conditioning involves associating one event with another in such a manner that the response to one event is associated, or transferred, to the other event.
Pavlov's work laid the foundation for the scientific analysis of behavior. Pavlov's work was seminal in the formulation of modern psychology and many psychiatric treatment programs. Classical conditioning is often referred to as Pavlovian conditioning, and much of the terminology associated with those concepts derives from Pavlov's famous experiments using quantitative measurement of salivary secretion in dogs as a measure of reflex or response to food stimulus. More specifically, Pavlovian refers to the conditioning of responses to previously neutral stimuli.
According to Pavlov, an unconditioned stimulus (meat) was a stimulus that elicited an unconditioned response (salivation). A conditioned stimulus (Pavlov's bell) was a previously neutral stimulus that did not normally elicit a response until after being paired or otherwise associated with an unconditioned stimulus (meat). Ultimately Pavlov was able to observe a conditioned response (salivation to a bell).
Important psychological principles were ultimately derived from Pavlov's work, including concepts related to habituation (the loss of potency by a stimulus caused by overuse of that stimulus so that greater or more intense presentation of the stimulus is required to elicit response), generalization (responses to stimuli other than the conditioned stimulus in a manner similar to the conditioned stimulus), discrimination (Pavlov demonstrated that dogs could discriminate between high and low pitch tones as conditioning stimuli), and extinction (the disappearance of a conditioned response when a conditioning stimulus is repeatedly presented without the unconditioned stimulus). Other important Pavlovian-derived psychological models involve spontaneous recovery, higher order conditioning, sensory preconditioning, and counter conditioning.
Pavlov was often at odds with the post-revolutionary communist government. At great peril to himself, he often argued passionately against the triumphant Bolsheviks. Vladimir Lenin (1870-1924) personally refused to allow Pavlov to move his work abroad. In response, Pavlov resisted the Bolshevik hierarchy by refusing to accept the privileges accorded other scientists of his ability and achievement. For instance, Pavlov refused extra food rations not available to his co-workers.
In 1924, Pavlov resigned his professorship in protest of expulsions of students whose families refused to quit the clergy. Even under the iron dictatorial hand of Lenin's successor, Joseph Stalin (1879-1953), Pavlov continued to be a thorn to the communist government. By 1927 Pavlov found himself isolated in the Soviet Academy of Sciences, where he railed against increasing political intrusions into matters of science. At a time when many were put to death for far less, Pavlov bravely defied Stalin and his commissars (Pavlov actually began to deny them actual physical access to his laboratory). By the mid-1930s, however, Pavlov's criticisms of the Soviet government gradually diminished as Pavlov balanced the dangers of Nazi fascism looming on the Western border and the growing agitation with an Imperial Japan to the East with his personal dislike for the communist system.
BRENDA WILMOTH LERNER
Pavlov, Ivan Petrovich
PAVLOV, IVAN PETROVICH
(1849–1936), Russian physiologist and Nobel Prize winner.
Ivan Pavlov was born in Ryazan. His father, a local priest, wanted him to attend the theological seminary, but Pavlov's interest in natural sciences led him to enroll in St. Petersburg University in 1870. In 1883 he completed his doctoral dissertation and in 1890 became professor and head of the physiology division of the St. Petersburg Institute of Experimental Medicine, where he remained until 1925. Pavlov's work on the functioning of the digestive system earned him the Nobel Prize in 1904. His originality lay in his approach to physiology, which considered the coordinated functioning of the organism as a whole, as well as his innovative surgical technique, which allowed him to observe digestion in live animals.
Pavlov's most well known research involved the study of conditioned reflexes. In his famous experiment, he placed a dog in a room free of all distractions. He found that the dog, accustomed to hearing a bell ring when being fed, would eventually salivate at the sound of the bell alone. Pavlov also applied his findings to the human nervous system. His work advanced the understanding of physiology and influenced international developments in medicine, psychology, and pedagogy.
Pavlov did not support the Bolshevik Revolution and in 1920 asked for permission to leave with his family. Vladimir Lenin, aware of the international prestige Pavlov brought to science in the Soviet Union, personally intervened to guarantee the resources for Pavlov to continue his research. In 1935, the International Congress of Physiologists awarded Pavlov the distinction of world senior physiologist. He died of pneumonia in Leningrad at the age of eighty-seven.
See also: education
Joravsky, David. (1989). Russian Psychology: A Critical History. Cambridge, MA: Blackwell Publishers.
Sharon A. Kowalsky
Pavlov, Ivan Petrovich
Ivan Petrovich Pavlov (ēvän´ pētrô´vĬch päv´ləf), 1849–1936, Russian physiologist and experimental psychologist. He was professor at the military medical academy and director of the physiology department at the Institute for Experimental Medicine, St. Petersburg, from 1890. Pavlov was a skillful ambidextrous surgeon; using dogs as experimental animals, he established fistulas from various parts of the digestive tract by which he obtained secretions of the salivary glands, pancreas, and liver without disturbing the nerve and blood supply. For his work on the physiology of the digestive glands he received the 1904 Nobel Prize in Physiology or Medicine. Using the same technique to create an artificial exterior pouch of the stomach, he experimented on nervous stimulation of gastric secretions and thus discovered the conditioned reflex (see behaviorism), which has had widespread influence in neurology and psychology. He also demonstrated that specific areas in the cerebral cortex are concerned with specific reflexes and based on these findings conceived of a mechanistic theory of human behavior that found political favor; in 1935 the government built a laboratory for him. His chief work was Conditioned Reflexes (1926, tr. 1927).
See biographies by B. P. Babkin (1949) and D. P. Todes (2014); studies by E. Strauss (1963), H. Cuny (tr. 1965), and I. P. Frolov (tr. 1937, repr. 1970).