Ivan Petrovich Pavlov (Иван Петрович Павлов, September 14, 1849 – February 27, 1936) was a Russian physiologist, psychologist, and physician. He was awarded the Nobel Prize in Physiology or Medicine in 1904 for research pertaining to the digestive system. Pavlov is widely known for first describing the phenomenon of classical conditioning.
In the 1890s, Pavlov was investigating the gastric function of dogs by externalizing a salivary gland so he could collect, measure, and analyze the saliva and what response it had to food under different conditions. He noticed that the dogs tended to salivate before food coated with chili powder was actually delivered to their mouths, and set out to investigate this "psychic secretion", as he called it.
He decided that this was more interesting than the chemistry of saliva, and changed the focus of his research, carrying out a long series of experiments in which he manipulated the stimuli occurring before the presentation of food. He thereby established the basic laws for the establishment and extinction of what he called "conditional reflexes" — i.e., reflex responses, like salivation, that only occurred conditionally upon specific previous experiences of the animal. These experiments were carried out in the 1890s and 1900s, and were known to western scientists through translations of individual accounts, but first became fully available in English in a book published in 1927.
Unlike many pre-revolutionary scientists, Pavlov was highly regarded by the Soviet government, and he was able to continue his research until he reached a considerable age. Moreover, he was praised by Lenin and as a Nobel laureate.
After the murder of Sergei Kirov in 1934, Pavlov wrote several letters to Molotov criticizing the mass persecutions which followed and asking for the reconsideration of cases pertaining to several people he knew personally.
In later life he was particularly interested in trying to use conditioning to establish an experimental model of the induction of neuroses. He died in Leningrad. His laboratory in Saint Petersburg has been carefully preserved as a museum.
Conscious until his very last moment, Pavlov asked one of his students to sit beside his bed and to record the circumstances of his dying. He wanted to create unique evidence of subjective experiences of this terminal phase of life. The great scientific courage of Pavlov is exhibited by this story: he tried to learn, and to increase knowledge of physiology, even on his deathbed.
Pavlov performed and directed experiments on digestion which earned him the 1904 Nobel Prize in Physiology and Medicine Experiments included surgically extracting portions of the digestive system from animals, severing nerve bundles to determine the effects, and implanting fistulas between digestive organs and an external pouch to examine the organ's contents. This research served as a base for broad research on the digestive system.
Further work on reflex actions involved involuntary reactions to stress and pain. Pavlov extended the definitions of the four temperament types under study at the time: phlegmatic, choleric, sanguine, and melancholic. Pavlov and his researchers observed and began the study of transmarginal inhibition (TMI), the body's natural response of shutting down when exposed to overwhelming stress or pain. This research showed how all temperament types responded to the stimuli the same way, but different temperaments move through the responses at different times. He commented "that the most basic inherited difference. .. was how soon they reached this shutdown point and that the quick-to-shut-down have a fundamentally different type of nervous system.
Carl Jung continued Pavlov's work on TMI and correlated the observed shutdown types in animals with his own introverted and extroverted temperament types in humans. Introverted persons, he believed, were more sensitive to stimuli and reached a TMI state earlier than their extroverted counterparts. This continuing research branch is gaining the name highly sensitive persons.
William Sargant and others continued the behavioral research in mental conditioning to achieve memory implantation and brainwashing (any effort aimed at instilling certain attitudes and beliefs in a person).
Pavlov's research on conditional reflexes greatly influenced not only science, but also popular culture. The phrase "Pavlov's dog" is often used to describe someone who merely reacts to a situation rather than use critical thinking. Pavlovian conditioning was a major theme in Aldous Huxley's dystopian novel, Brave New World, and also to a large degree in Thomas Pynchon's Gravity's Rainbow.
It is popularly believed that Pavlov always signaled the occurrence of food by ringing a bell. However, his writings record the use of a wide variety of stimuli, including whistles, metronomes, tuning forks, and a range of visual stimuli, in addition to ringing a bell. Catania cast doubt on whether Pavlov ever actually used a bell in his famous experiments. Littman tentatively attributed the popular imagery to Pavlov’s contemporaries Vladimir Mikhailovich Bekhterev and John B. Watson, until Thomas found several references that unambiguously stated Pavlov did, indeed, use a bell.