Psychology Classics


Conditioned Reflexes


Ivan Pavlov

You have probably heard of Pavlov and his famous dogs, but who was he and what was his contribution to psychology? Born in 1849 in central Russia, he was expected to follow his father's footsteps and become a priest in the Eastern Orthodox church, but inspired by reading Darwin he escaped the local seminary and went to study chemistry and physics in St Petersburg.

At university Pavlov became passionate about physiology, and worked in the labs of several eminent professors. In time he became well known for his work as a specializing in digestion and the nervous system. As a physiologist Pavlov did not think much of the new science of psychology, yet it was this work that would lead him to insights on 'conditioning', or the way that animals (including humans) develop new reflexes in order to respond to their environment.

Conditioned Reflexes, translated from the Russian, is a collection of lectures first given by Pavlov at the Military Medical Academy in St Petersburg in 1924, and subsequently turned into a book. In mind-numbing detail, it summarizes the 25 years of research carried out by his team that ultimately led to a Nobel Prize. Below we look at what Pavlov actually discovered and its implications for human psychology.

Animals as machines

Pavlov begins the book by noting the lack of knowledge about the brain. He regrets that the brain had become the domain of psychology, when it should be the preserve of physiologists who could determine the facts about the brain's physics and chemistry.

But he takes his hat off to philosopher Rene Descartes, who three centuries earlier had described animals as machines who reacted predictably according to stimuli in their environment in order to achieve a certain equilibrium with it. These reactions were part of the nervous system and occurred along set nerve pathways.

One of these reflex reactions is the creation of saliva, and it was the action of the digestive glands in dogs that Pavlov was initially investigating. He wanted to chemically analyze the differences in saliva produced in response to food under different conditions.

But in his early experiments Pavlov noticed a strange thing. There was a psychological element to the dogs' saliva reflex: that is, they would begin to salivate simply when they thought they were about to get food. Descartes' idea of the automatic reaction was clearly not so simple; he wanted to investigate further.

Creating reflexes

Pavlov decided to try out a range of stimuli on the dogs to see what exactly would provoke their saliva secretion, if it was not just a simple automatic reflex. So that his experiments would be in real time, he had to perform a minor operation so that some of the dog's saliva passed through a hole to the outside of the cheek and into a pouch so where the amounts produced could be measured.

He would give the dogs' various stimuli such as the beat of a metronome, buzzers, bells, bubbling and crackling sounds, plus showing a black square, heat, touching the dog in various places, and intermittent flashes of a lamp. Each of these would occur just prior to the giving of food, so when another time the dog heard, saw or felt a certain stimulus, he would start to salivate even if the food had not appeared. Merely the sound of a beating metronome would produce saliva even if no food was to be seen; physiologically there was no difference between the dog's reaction when he heard the metronome and what happened when he actually saw food. For the dog, the metronome – rather than a bowl of meat – came to 'mean' food.

Pavlov realized that there were two types of reflexes or responses of an animal to its environment:

  • the natural or unconditioned reflex (e.g. A dog's salivation when it begins to eat, to aid its digestion); and
  • the acquired or conditioned reflex, which arose through unconscious learning (e.g. When a dog begins to salivate at the sound of a bell, because the sound 'equates' to food).

The fact that reflexes could be instilled so that they became part of the animal's natural functioning made Pavlov realize that if an animal was a machine responding to its environment, then it was a very complex machine. He showed that the cerebral cortex, the most advanced part of the brain, and the nervous pathways linking to it, was very malleable. So called 'instincts' could be learned – and unlearned, for he was also able to demonstrate that reflexes could also be inhibited or extinguished by associating food with something the dog doesn't like.

Yet Pavlov also noted limits to the creation of conditioned reflexes. They would either wear off over time, or the dogs would sometimes not bother to respond and just fall asleep. Pavlov concluded that the cerebral cortex cannot be overworked or changed too much. It seemed that a dog's survival and proper functioning required it to retain a certain amount of stability in its brain wiring.

Advanced environment-responding machines

Pavlov observed two levels in the way that an animal responds to its environment. There is first a  'neuro-analysis' in which it uses its senses to work out what things are, then a 'neuro-synthesis' to establish how something fits into its existing reactions and knowledge. In order to survive, for instance, a dog must be able to quickly determine if something is a threat to it or not.

Some of Pavlov's experiments involved removing a dog's whole cerebral cortex. This turned the dog into little more than a reflex machine. It retained its unconditioned reflexes that were hardwired into its brain and nervous system, but was not able to properly respond to its environment - it could still walk, but if it came to even a small obstacle like the leg of a table it did not know what to do. In contrast, with a normal dog even if there is a minute change in environmental stimulus or something new, an 'investigatory reflex' will see the animal prick up its ears, or sniff the stimulus. A dog may spend a lot of time simply 'investigating' in order that its reflexes to its environment are fully up to date.

Pavlov knew that the results of his experiments did not just apply to dogs. The more advanced the organism, he said, the greater its ability “to multiply the complexity of its contacts with the external world and to achieve a more and more varied and exact adaptation to external conditions.” 'Culture' and 'society' could be understood as a complex system of the management of reflexes, with humans only different to dogs to the extent that conditioned reflexes had surpassed the natural ones. While dogs could develop advanced social and territorial knowledge as its optimal response to environment, human beings had responded by creating 'civilization'.

Man and dog: the similarities

The final chapter of Conditioned Reflexes concerns the applications of Pavlov's work to humans. Given that a human has a much more complex cerebral cortex than a dog, Pavlov was wary of reading too much into his own work. However, he noted the following parallels.

  • The way human beings are trained, disciplined and enculturated is not that different to how dogs are taught to do things. We know that the best way to learn something is to do it in stages, in the same way that the conditioned reflexes of the dogs was effected in steps. And as found with dogs, we humans have to unlearn things as well as learning them.
  • Pavlov had a special soundproofed building created for his experiments because he found that external stimuli affected the ability to condition reflexes. In the same way, most of us cannot study a book if a movie is being shown in front of it; we find it hard to 'get back into it' after a holiday or some break from routine. As with the dogs, neuroses and psychoses occur as the result of extreme stimulation that cannot be properly incorporated into existing thinking and reactions.
  • The reactions of Pavlov's dogs could not be predicted. He recalls that when one of Petrograd's famous floods swept through the experimental quarters, some dogs grew excited, others frightened, some withdrew. In the same way, he noted, we can never predict how a person will react emotionally to, for instance, a strong insult or to the loss of a loved one. These reactions seemed to mirror the two common psychological reactions to shock recognized in both dogs and humans: neurasthenia (fatigue, withdrawing, immobilization); or hysteria (neurotic excitation).

With the last point, Pavlov's implication was that evolution has ensured we cannot not react to a major event – we must take account of it some way. To eventually return to a state of stability, we have to incorporate what we have experienced. The phenomenon of 'fight or flight' in the face of a challenge is the nervous system's manner of self-protection in the short term. In the longer term, the fact that we have had a reaction ensures that we can eventually return to a state of equilibrium with our environment.

Final comments

Pavlov saw the cerebral cortex as a complicated switchboard in which groups of cells were responsible for different reflexes. There was always room for more reflexes to be created, but also capacity for existing ones to be altered. His dogs did have an automatic nature to them, but at the same time their reflexes and reactions were changeable. The implication for humans? Although we live for the most part through habit or enculturation, we are in a position to change our behavior patterns. We are as susceptible to conditioning as any animal, yet at the same time we also have the ability to break our own patterns if ultimately they prove not to be in our interest. Via feedback from our environment we learn what are effective responses to life and what are not. 

Pavlov's research had a major impact on the Behavioral school of psychology, which held that humans were little different to dogs in that we have predictable reactions to stimuli and could be conditioned into certain ways of behavior. For the hard-core behaviorist, the idea of free will is a myth – whatever inputs are made into a person will yield certain outputs in terms of attitudes or behaviors. Yet Pavlov's own observations seem to contradict this; for instance, he noted that that many of the dogs' reactions were not predictable. Even when conditioning had occurred, there was still room for canine personalities to be expressed. Given our much larger cerebral cortexes, appreciate then how much more room for varied expression - or 'responses to environment' - we must enjoy. 

Conditioned Reflexes has a very plodding, scientific style. Reflecting his love of empirical fact, order and discipline, Pavlov does not allow much of his personality to come through. Yet he was a fascinating figure. Although critical of communism, he flourished after the Bolshevik revolution, with Lenin handing down a decree that his work was “of enormous significance to the working classes of the whole world”.

Given his distrust of the claims of the subject, it is ironic that his name has come to be associated with psychology. His focus on measurable physiological reaction alone was almost the opposite approach of the Freudian immersion in 'inner drives and wishes', yet that focus enabled psychology to rest on harder scientific ground.

Source: 50 Psychology Classics: Who We Are, How We Think, What We Do. Insight and inspiration from 50 key books (Nicholas Brealey, London & Boston), Tom Butler-Bowdon.

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I P Pavlov

Ivan Petrovich Pavlov was born in 1849 in Ryazan, the oldest of eleven children.

His time at the University of St Petersburg produced acclaimed work on the pancreatic nerves, and on receiving his degree in 1875 he continued his studies at the Imperial Medical Academy. There he gained a fellowship and later a position as professor of physiology. His doctorate concerned the centrifugal nerves of the heart.

In 1890 he set up the physiology department of the Institute of Experimental Sciences in St Petersburg, where he did most of his work on digestion and conditioned reflexes. He was in charge of a large team of mostly young scientists.

His many honors include membership of the Russian Academy of Sciences, winning the 1904 Nobel Prize, and in 1915 France's Order of the Legion of Honor. His marriage to Seraphima in 1881 produced four children, one who went on to become a physicist.

Pavlov was still working in his labs when he died in 1936, at the age of 87. ©2015 All rights reserved.
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