The Pavlov’s Dog experiment is among the most famous in the history of psychology. As the story goes, in 1901 Russian scientist Ivan Pavlov observed that if a dog was presented with food, it would begin to salivate in anticipation. If, however, that food was repeatedly presented alongside a separate stimulus – like the ringing of a bell – eventually the dog would begin to salivate in response to the bell alone, having come to associate that stimulus with the arrival of food. The discovery of this process, known as Pavlovian or classical conditioning, revolutionized the study of psychology and directly inspired the work of such giants as John Watson and B.F. Skinner. And so embedded are Pavlov’s experiments in our collective consciousness that the term “Pavlov’s dog” has become shorthand for anything – or anyone – that reacts unthinkingly to some stimulus. However, this widely-retold story is a grossly simplified – and sanitized – version of Pavlov’s actual experiments. In reality, Pavlov did not even set out to study animal behaviour, and his experimental methods were less The Dog Whisperer and more Frankenstein. For any animal lovers watching, a word of warning: things are going to get very, very gross.

Ivan Petrovich Pavlov was born on September 14, 1949 in Ryazan, central Russia. At first the young Pavlov sought to follow his father, Peter Dmitrievich, into the priesthood, studying first at the church school and then the local seminary. However, major changes sweeping the country would soon divert him from this religious path. In 1861, Tsar Alexander II emancipated Russia’s 23 million feudal serfs, unleashing a wave of progressive thought across the Empire. Among the ideas being widely discussed were the evolutionary theories of Charles Darwin, and it was these which in 1869 inspired Pavlov to leave the seminary and enrol in the physics and mathematics department at Saint Petersburg University. Eventually Pavlov would reject religion altogether, declaring:

“[Scientific Truth] is for me a kind of God, before whom I reveal everything, before whom I discard wretched worldly vanity. I always think to base my virtue, my pride, upon the attempt, the wish for truth, even if I cannot attain it.”

It is worth noting here that the majority of Pavlov’s denouncements of religion were nowhere near as lyrical or diplomatic. Pavlov forbade his wife, Seraphima, from attending church or praying, and upon seeing a medical student stop in front of a church and cross themselves, once exclaimed: “Think about it! A naturalist, a physician, but he prays like an old woman in an almshouse!”

Indeed, Pavlov’s colleagues described him as a difficult man to work with: punctilious, demanding, irritable, and prone to frequent fits of rage. His angry outbursts knew no bounds and were directed against any and all who crossed him, from students and assistants to colleagues, supervisors, and even – as we shall later see – Josef Stalin. He was also a terrible husband, frequently neglecting his wife and cheating on her with his female lab assistance. But for all his social flaws, Pavlov’s obsession with empirical data and his singular attention to detail would serve him well in his scientific endeavours.

While studying in St. Petersburg, Pavlov became fascinated with human physiology, in particular the work of Russian scientist Ivan Secherov. Sechenov was a proponent of reflex theory, a school of thought originated by 17th Century French philosopher Rene Descartes which saw human beings as mere machines and which posited that every human behaviour, no matter how complex, was composed of a combination of simple mechanistic reflexes. According to Secherov, if these individual responses could be picked apart and studied in isolation, then the complete function of the human body could be understood. The unspoken implication, of course, was that free will was an illusion and that, in the words of American behaviourist John Watson: “…the behavior of animals can be investigated without appeal to consciousness.”

In 1875, the year he graduated from Saint Petersburg University, Pavlov published his first scientific paper, a highly-acclaimed treatise on the physiology of the pancreatic nerves. Pavlov next enrolled at the Medical Surgical Academy, and after graduating in 1879 accepted the directorship of the Physiological Laboratory of the famous clinician Sergey Botkin. It was here that Pavlov first developed a research technique he called “chronic experimentation.” While vivisection – the dissection of live animals to study biological functions – was common practice at the time, such invasive and traumatic surgeries tended to skew experimental results and invariably resulted in the death of the animal. Instead, Pavlov trained dogs to lie still on the operating table so he could insert needles into their blood vessels and nerves and monitor their function in real time. Using these methods, Pavlov determined that the beating of the heart is regulated by four main nerves – a discovery which formed the basis of his 1883 doctoral thesis.

In 1890, Pavlov accepted the directorship of the Department of Physiology at Saint Petersburg’s Institute of Experimental Medicine – a position he would hold for the rest of his life. It was at the institute that Pavlov would carry out the most important work of his career – not on psychology or animal behaviour, but digestion. At the time, little was known about the actual physiology of digestion – about how the passage of food through the gut stimulates the release of various gastric juices. For this research, Pavlov turned once more to dogs – and to his technique of chronic experimentation.

In order to study the intricacies of the digestive process as accurately as possible, Pavlov turned his dogs into living scientific instruments. Each animal was given an operation wherein their esophagus was severed and pulled through their neck, such that no matter how much the dog ate, no food would reach its stomach. This allowed Pavlov and his colleagues to study the effects on the digestive system of the dog tasting or merely smelling or seeing food. Pavlov next cut holes in the dogs’ sides and attached short tubes to various digestive organs such as the stomach, pancreas, gallbladder, and salivary glands. These tubes were connected to small bags or vials so the precise amount of digestive juices excreted could be measured. To prevent the dogs from moving and tearing out the tubes they were kept restrained in special harnesses mounted in wooden frames.

Though gruesome and cruel by modern standards, the technique proved extremely effective – so effective, in fact, that it even provided Pavlov’s lab with a useful source of extra income. At the time, pepsin – a digestive enzyme found in gastric juice – was a popular treatment for indigestion, being mixed into all sorts of consumer products from soft drinks to chewing gum. Being free of food particles and other contamination, Pavlov’s pepsin was of higher quality than anything on the market, prompting him to create a “gastric juice factory”

“An assistant was hired and paid thirty rubles a month to oversee the facility. Five large young dogs, weighing sixty to seventy pounds and selected for their voracious appetites, stood on a long table harnessed to the wooden crossbeam directly above their heads. Each was equipped with an esophagotomy and fistula from which a tube led to the collection vessel. Each ‘factory dog’ faced a short wooden stand tilted to display a large bowl of minced meat.”

By 1904, the lab was selling more than three thousand litres of gastric juice per year, allowing it to increase its budget by nearly 70%.

Over the following two decades, Pavlov and his colleagues would carry out hundreds of experiments on the dogs, teasing out the intricate chemical and nervous connections between the organs of the digestive system. It was for this research and not his more famous behavioural studies that Pavlov was awarded the 1904 Nobel Prize in Physiology and Medicine. Nevertheless, it was Pavlov’s meticulous approach to his digestion research that would lead him directly to his greatest discovery.

In 1901, while measuring the output of his dogs’ salivary glands in response to the sight and smell of food, Pavlov noticed that the mere sight of the scientists who normally brought the food would cause the dogs to salivate. This phenomenon, known as “psychic salivation,” had been observed before, and Pavlov initially dismissed it as yet another automatic reflex. However, Pavlov soon observed that different dogs associated different stimuli with food, while others made no associations at all. This flew in the face of Sergey Sechenov’s assertions that all reflexes and behaviours were hardwired and immutable; as Pavlov could plainly see, even a response as basic as salivating in the presence of food could be easily altered – or conditioned – through experience. This observation inspired Pavlov to more closely study the possibilities – and limits – of the conditioning process.

Contrary to popular belief, Pavlov never used a bell in his experiments. Indeed, Pavlov found bells particularly unsuited to his purposes, their precise tone being too difficult to consistently reproduce.

He instead used a variety of devices including tuning forks, electric buzzers, and metronomes whose consistency allowed him to determine just how specific a stimulus a dog could be trained to respond to. For example, when a dog was presented with food and a metronome, it would salivate at the sound of any metronome. But if a metronome of a certain frequency was presented several times in a row, the dog would only salivate when it heard that particular frequency. Pavlov also experimented with other sensory stimuli, such as heat, shapes, flashes of light, touching the dogs in various places, and electric shocks. So how did the image of Pavlov ringing a bell come to dominate the popular consciousness? According to Pavlov biographer Daniel P. Todes, this misconception may stem from Pavlov’s use of the word zvonok, which literally translates as “buzzer” but is often mistranslated as “bell.” Alternatively, the association may derive from the later research of psychologists Vladimir Bekhterev and John Watson, who did use bells in their experiments.

Also frequently misunderstood are Pavlov’s conclusions regarding his conditioning experiments. Though inspired by pure behaviourists like Sergey Sechenov, Pavlov himself never believed that animals and were purely mechanistic beings whose behaviour could be programmed at will. In his writings Pavlov freely acknowledged that the dogs in his experiments all had their own unique temperaments and personalities and responded to his conditioning efforts in different and unpredictable ways. In many cases the dogs failed to respond to the conditioning stimuli and simply fell asleep, while in others the conditioned responses wore off over time. Furthermore, unconditioned “hard-wired” behaviours could be extinguished through negative reinforcement. For example, in yet another ethically-dubious 1914 experiment, Pavlov applied electric shocks to certain parts of dogs’ bodies while they ate. Eventually, further shocks induced the dogs to salivate. But when the shocks were applied to other parts of the dogs’ bodies, they grew confused and aggressive:

“A hitherto quiet dog began to squeal in its stand, kept wriggling about, and bit through the tubes connecting the animal’s room with the observer’s.”

Similarly, a cat that was shocked while eating a mouse spat out its meal and became frightened and immobile at the mere sight of a mouse. Such induced neuroses were found to be largely permanent, lasting months or even years. Descending further into Dr. Frankenstein territory, Pavlov even removed dogs’ cerebral cortexes – seat of their higher mental functions – in order to turn them into purely reflexive beings. While still retaining their natural, unconditioned responses, such creatures were incapable of learning or even simple decision-making – such as whether to go around an obstacle placed in their path. As a result, Pavlov concluded that higher brain functions, no matter how limited, had a powerful mediating influence on behaviour and were essential to allowing animals to interact with and adapt to the world around them:

“It would be stupid to reject the subjective world. Our actions, all forms of social and personal life are formed on this basis. The question is how to analyze this subjective world.”

Indeed, even the term “conditioned response,” commonly applied to Pavlov’s work, is the result of yet another mistranslation. Pavlov’s original term translates to “conditional response,” acknowledging the variability and subjectivity of the conditioning process. And while many of his contemporaries feared that a greater understanding of the inner workings of the mind would eventually lead to the enslavement of mankind, Pavlov argued the opposite, declaring in 1927:

“We would have freedom of the will in proportion to our knowledge of the brain, just as we had passed from a position of slave to a lord of nature.”

Nonetheless, Pavlov’s work would be widely misinterpreted by his scientific heirs, many of whom would distort his findings to support a purely behaviourist view of human behaviour. Among these was John Watson, who in 1924 boldly claimed:

“Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.”

But perhaps the worst culprits when it came to misinterpreting Pavlov were the Bolsheviks. When Vladimir Lenin took control of the country in 1917, Pavlov and his collaborators were treated like any other Soviet citizens, their laboratory funding being confiscated as property of the state. For three years they struggled to keep warm and fed, with many of Pavlov’s assistants dying of starvation and hypothermia. Finally, in 1920, Pavlov wrote to Lenin seeking permission to emigrate from Russia and continue his research elsewhere. Lenin immediately grasped the public relations implications of losing the country’s most celebrated scientist, and saw to it that Pavlov and his staff received unlimited funding and carte blanche to pursue their research. It didn’t hurt that the Soviet leadership saw Pavlov as psychology’s answer to Karl Marx, and his behaviourist theories as a real-world manifestation of dialectical materialism. And while Pavlov actively rejected this interpretation of his work, this misunderstanding allowed his laboratory to prosper at a time when many intellectuals were being rounded up as suspected enemies of the state.

While most scientists in Pavlov’s position would have kept their heads down and tried not to rock the boat, Pavlov was vocal in his denunciation of the Communist regime, declaring in one public speech:

“Of course, in the struggle between labor and capital the government must stand for the protection of the worker. But what have we made of this? That which constitutes the culture, the intellectual strength of the nation, has been devalued, and that which for now remains a crude force, replaceable by a machine, has been moved to the forefront. All this, of course, is doomed to destruction as a blind rejection of reality.”

This outspoken opposition carried on well into Stalin’s reign of terror, with Pavlov even writing the Soviet leader to declare that his purge of intellectuals made him “ashamed to be called a Russian.” And when Stalin sent an agent to purge his laboratory of political undesirables, Pavlov proceeded to calmly and rationally kick said agent down the stairs.Whether Pavlov was astoundingly brave or, being well into his 70s, had simply run out of fucks to give, we shall likely never know. But while a man with less Kremlin-sized balls would have been immediately arrested and shot or shipped off to the Gulag, amazingly Pavlov got away with it, with Nikolai Bukharin, Stalin’s right-hand man, grudgingly admitting:

“I know that he does not sing the ‘Internationale,’ but despite all his grumbling, ideologically (in his works, not in his speeches) he is working for us.”

Under the protection of the Soviet State, Pavlov built the Institute of Experimental Medicine into a  world-renowned centre of physiology and psychology research, and continued to make important discoveries up until his death from double pneumonia on February 27, 1936. Still considered a hero of the Soviet Union despite his anti-communist rhetoric, his funeral was attended by one hundred thousand mourners.

Such was the eventful and complicated career of Ivan Pavlov, scientific genius, torturer of dogs, terrible colleague and husband, and possibly the bravest man in the Soviet Union. Yet the impact of his work on the fields of physiology and psychology is immeasurable, with Pavlov being the 24th most cited psychologist of the 20th Century. Misremembered as they are, his groundbreaking experiments live on in our collective memory, and are the reason why to most people the name “Pavlov” still rings a bell.

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