what was ivan pavlov experiment

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Laws of conditioned reflex

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What did Ivan Pavlov study?

What was ivan pavlov best known for, what were ivan pavlov’s contributions, what was ivan pavlov’s first job.

Ivan Pavlov

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• History Today - Death of Ivan Pavlov
• Athabasca University - Psychology Learning Resources - Biography of Ivan Pavlov (1849 - 1936)
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• The Nobel Prize - Biography of Ivan Pavlov
• Age of the Sage - Transmitting the Wisdoms of the Ages - Biography of Ivan Pavlov
• Verywell Mind - Ivan Pavlov and His Discovery of Classical Conditioning
• Academia - Theory of Ivan Petrovich Pavlov and application in ELT
• GoodTherapy - Ivan Pavlov (1849-1936)
• Ivan Pavlov - Student Encyclopedia (Ages 11 and up)
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Ivan Pavlov gave up studying theology to enter the University of St. Petersburg , where he studied chemistry and physiology . After receiving an M.D. at the Imperial Medical Academy in St. Petersburg , he studied in Germany under the direction of the cardiovascular physiologist Carl Ludwig and the gastrointestinal physiologist Rudolf Heidenhain.

Ivan Pavlov developed an experiment testing the concept of the conditioned reflex . He trained a hungry dog to salivate at the sound of a metronome or buzzer, which was previously associated with the sight of food . He later developed an approach that emphasized the importance of conditioning in studies relating human behaviour to the nervous system .

In addition to his conditioning work, Ivan Pavlov devised an operation to prepare a miniature stomach , which was isolated from ingested foods but retained its vagal nerve supply. The procedure allowed him to study the gastrointestinal secretions in animals . For his efforts he received the Nobel Prize for Physiology or Medicine in 1904.

Having worked with Carl Ludwig , Ivan Pavlov’s first independent research was on the physiology of the circulatory system . From 1888 to 1890, in St. Petersburg, he investigated cardiac physiology and blood pressure regulation. He became so skillful as a surgeon that he could introduce a catheter into a dog’s femoral artery almost painlessly.

Ivan Pavlov (born September 14 [September 26, New Style], 1849, Ryazan, Russia—died February 27, 1936, Leningrad [now St. Petersburg]) was a Russian physiologist known chiefly for his development of the concept of the conditioned reflex . In a now-classic experiment, he trained a hungry dog to salivate at the sound of a metronome or buzzer, which was previously associated with the sight of food. He developed a similar conceptual approach, emphasizing the importance of conditioning , in his pioneering studies relating human behaviour to the nervous system . He was awarded the Nobel Prize for Physiology or Medicine in 1904 for his work on digestive secretions.

Pavlov, the first son of a priest and the grandson of a sexton, spent his youth in Ryazan in central Russia . There, he attended a church school and theological seminary, where his seminary teachers impressed him by their devotion to imparting knowledge. In 1870 he abandoned his theological studies to enter the University of St. Petersburg , where he studied chemistry and physiology. After receiving the M.D. at the Imperial Medical Academy in St. Petersburg (graduating in 1879 and completing his dissertation in 1883), he studied during 1884–86 in Germany under the direction of the cardiovascular physiologist Carl Ludwig (in Leipzig) and the gastrointestinal physiologist Rudolf Heidenhain (in Breslau).

Having worked with Ludwig, Pavlov’s first independent research was on the physiology of the circulatory system . From 1888 to 1890, in the laboratory of Botkin in St. Petersburg, he investigated cardiac physiology and the regulation of blood pressure .

He became so skillful a surgeon that he was able to introduce a catheter into the femoral artery of a dog almost painlessly without anesthesia and to record the influence on blood pressure of various pharmacological and emotional stimuli. By careful dissection of the fine cardiac nerves , he was able to demonstrate the control of the strength of the heartbeat by nerves leaving the cardiac plexus; by stimulating the severed ends of the cervical nerves, he showed the effects of the right and left vagal nerves on the heart.

Pavlov married a pedagogical student in 1881, a friend of the author Fyodor Dostoyevsky , but he was so impoverished that at first they had to live separately. He attributed much of his eventual success to his wife, a domestic, religious, and literary woman, who devoted her life to his comfort and work. In 1890 he became professor of physiology in the Imperial Medical Academy, where he remained until his resignation in 1924. At the newly founded Institute of Experimental Medicine, he initiated precise surgical procedures for animals, with strict attention to their postoperative care and facilities for the maintenance of their health .

During the years 1890–1900 especially, and to a lesser extent until about 1930, Pavlov studied the secretory activity of digestion . While working with Heidenhain, he had devised an operation to prepare a miniature stomach , or pouch; he isolated the stomach from ingested foods, while preserving its vagal nerve supply. The surgical procedure enabled him to study the gastrointestinal secretions in a normal animal over its life span. This work culminated in his book Lectures on the Work of the Digestive Glands in 1897.

By observing irregularities of secretions in normal unanesthetized animals, Pavlov was led to formulate the laws of the conditioned reflex, a subject that occupied his attention from about 1898 until 1930. He used the salivary secretion as a quantitative measure of the psychical, or subjective, activity of the animal, in order to emphasize the advantage of objective, physiological measures of mental phenomena and higher nervous activity. He sought analogies between the conditional (commonly though incorrectly translated as “conditioned”) reflex and the spinal reflex.

According to the English physiologist Sir Charles Sherrington , the spinal reflex is composed of integrated actions of the nervous system involving such complex components as the excitation and inhibition of many nerves , induction (i.e., the increase or decrease of inhibition brought on by previous excitation), and the irradiation of nerve impulses to many nerve centres. To these components, Pavlov added cortical and subcortical influences, the mosaic action of the brain , the effect of sleep on the spread of inhibition, and the origin of neurotic disturbances principally through a collision, or conflict, between cortical excitation and inhibition.

Beginning about 1930, Pavlov tried to apply his laws to the explanation of human psychoses . He assumed that the excessive inhibition characteristic of a psychotic person was a protective mechanism—shutting out the external world—in that it excluded injurious stimuli that had previously caused extreme excitation. In Russia this idea became the basis for treating psychiatric patients in quiet and nonstimulating external surroundings. During this period Pavlov announced the important principle of the language function in human beings as based on long chains of conditioned reflexes involving words. The function of language involves not only words, he held, but an elaboration of generalizations not possible in animals lower than humans.

Classical Conditioning: How It Works With Examples

Saul McLeod, PhD

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Classical conditioning (also known as Pavlovian or respondent conditioning) is learning through association and was discovered by Pavlov , a Russian physiologist. In simple terms, two stimuli are linked together to produce a new learned response in a person or animal.

John B. Watson proposed that the process of classical conditioning (based on Pavlov’s observations) was able to explain all aspects of human psychology.

If you pair a neutral stimulus (NS) with an unconditioned stimulus (US) that already triggers an unconditioned response (UR) that neutral stimulus will become a conditioned stimulus (CS), triggering a conditioned response (CR) similar to the original unconditioned response.

Everything from speech to emotional responses was simply patterns of stimulus and response. Watson completely denied the existence of the mind or consciousness. Watson believed that all individual differences in behavior were due to different learning experiences.

Watson (1924, p. 104) famously said:

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 the race of his ancestors.

How Classical Conditioning Works

There are three stages of classical conditioning. At each stage, the stimuli and responses are given special scientific terms:

Stage 1: Before Conditioning:

In this stage, the unconditioned stimulus (UCS) produces an unconditioned response (UCR) in an organism.

In basic terms, this means that a stimulus in the environment has produced a behavior/response that is unlearned (i.e., unconditioned) and, therefore, is a natural response that has not been taught. In this respect, no new behavior has been learned yet.

For example, a stomach virus (UCS) would produce a response of nausea (UCR). In another example, a perfume (UCS) could create a response of happiness or desire (UCR).

This stage also involves another stimulus that has no effect on a person and is called the neutral stimulus (NS). The NS could be a person, object, place, etc.

The neutral stimulus in classical conditioning does not produce a response until it is paired with the unconditioned stimulus.

Stage 2: During Conditioning:

During this stage, a stimulus which produces no response (i.e., neutral) is associated with the unconditioned stimulus, at which point it now becomes known as the conditioned stimulus (CS).

For example, a stomach virus (UCS) might be associated with eating a certain food such as chocolate (CS). Also, perfume (UCS) might be associated with a specific person (CS).

For classical conditioning to be effective, the conditioned stimulus should occur before the unconditioned stimulus, rather than after it, or during the same time. Thus, the conditioned stimulus acts as a type of signal or cue for the unconditioned stimulus.

In some cases, conditioning may take place if the NS occurs after the UCS (backward conditioning), but this normally disappears quite quickly. The most important aspect of the conditioning stimulus is the it helps the organism predict the coming of the unconditional stimulus.

Often during this stage, the UCS must be associated with the CS on a number of occasions, or trials, for learning to take place.

However, one trial learning can happen on certain occasions when it is not necessary for an association to be strengthened over time (such as being sick after food poisoning or drinking too much alcohol).

Stage 3: After Conditioning:

The conditioned stimulus (CS) has been associated with the unconditioned stimulus (UCS) to create a new conditioned response (CR).

For example, a person (CS) who has been associated with nice perfume (UCS) is now found attractive (CR). Also, chocolate (CS) which was eaten before a person was sick with a virus (UCS) now produces a response of nausea (CR).

Classical Conditioning Examples

Pavlov’s dogs.

The most famous example of classical conditioning was Ivan Pavlov’s experiment with dogs , who salivated in response to a bell tone. Pavlov showed that when a bell was sounded each time the dog was fed, the dog learned to associate the sound with the presentation of the food.

He first presented the dogs with the sound of a bell; they did not salivate so this was a neutral stimulus. Then he presented them with food, they salivated. The food was an unconditioned stimulus, and salivation was an unconditioned (innate) response.

He then repeatedly presented the dogs with the sound of the bell first and then the food (pairing) after a few repetitions, the dogs salivated when they heard the sound of the bell. The bell had become the conditioned stimulus and salivation had become the conditioned response.

Fear Response

Watson & Rayner (1920) were the first psychologists to apply the principles of classical conditioning to human behavior by looking at how this learning process may explain the development of phobias.

They did this in what is now considered to be one of the most ethically dubious experiments ever conducted – the case of Little Albert . Albert B.’s mother was a wet nurse in a children’s hospital. Albert was described as ‘healthy from birth’ and ‘on the whole stolid and unemotional’.

When he was about nine months old, his reactions to various stimuli (including a white rat, burning newspapers, and a hammer striking a four-foot steel bar just behind his head) were tested.

Only the last of these frightened him, so this was designated the unconditioned stimulus (UCS) and fear the unconditioned response (UCR). The other stimuli were neutral because they did not produce fear.

When Albert was just over eleven months old, the rat and the UCS were presented together: as Albert reached out to stroke the animal, Watson struck the bar behind his head.

This occurred seven times in total over the next seven weeks. By this time, the rat, the conditioned stimulus (CS), on its own frightened Albert, and fear was now a conditioned response (CR).

The CR transferred spontaneously to the rabbit, the dog, and other stimuli that had been previously neutral. Five days after conditioning, the CR produced by the rat persisted. After ten days, it was ‘much less marked’, but it was still evident a month later.

Carter and Tiffany (1999) support the cue reactivity theory, they carried out a meta-analysis reviewing 41 cue-reactivity studies that compared responses of alcoholics, cigarette smokers, cocaine addicts and heroin addicts to drug-related versus neutral stimuli.

They found that dependent individuals reacted strongly to the cues presented and reported craving and physiological arousal.

Panic Disorder

Classical conditioning is thought to play an important role in the development of Pavlov (Bouton et al., 2002).

Panic disorder often begins after an initial “conditioning episode” involving an early panic attack. The panic attack serves as an unconditioned stimulus (US) that gets paired with neutral stimuli (conditioned stimuli or CS), allowing those stimuli to later trigger anxiety and panic reactions (conditioned responses or CRs).

The panic attack US can become associated with interoceptive cues (like increased heart rate) as well as external situational cues that are present during the attack. This allows those cues to later elicit anxiety and possibly panic (CRs).

Through this conditioning process, anxiety becomes focused on the possibility of having another panic attack. This anticipatory anxiety (a CR) is seen as a key step in the development of panic disorder, as it leads to heightened vigilance and sensitivity to bodily cues that can trigger future attacks.

The presence of conditioned anxiety can serve to potentiate or exacerbate future panic attacks. Anxiety cues essentially lower the threshold for panic. This helps explain how panic disorder can spiral after the initial conditioning episode.

Evidence suggests most patients with panic disorder recall an initial panic attack or conditioning event that preceded the disorder. Prospective studies also show conditioned anxiety and panic reactions can develop after an initial panic episode.

Classical conditioning processes are believed to often occur outside of conscious awareness in panic disorder, reflecting the operation of emotional neural systems separate from declarative knowledge systems.

Cue reactivity is the theory that people associate situations (e.g., meeting with friends)/ places (e.g., pub) with the rewarding effects of nicotine, and these cues can trigger a feeling of craving (Carter & Tiffany, 1999).

These factors become smoking-related cues. Prolonged use of nicotine creates an association between these factors and smoking based on classical conditioning.

Nicotine is the unconditioned stimulus (UCS), and the pleasure caused by the sudden increase in dopamine levels is the unconditioned response (UCR). Following this increase, the brain tries to lower the dopamine back to a normal level.

The stimuli that have become associated with nicotine were neutral stimuli (NS) before “learning” took place but they became conditioned stimuli (CS), with repeated pairings. They can produce the conditioned response (CR).

However, if the brain has not received nicotine, the levels of dopamine drop, and the individual experiences withdrawal symptoms therefore is more likely to feel the need to smoke in the presence of the cues that have become associated with the use of nicotine.

Classroom Learning

The implications of classical conditioning in the classroom are less important than those of operant conditioning , but there is still a need for teachers to try to make sure that students associate positive emotional experiences with learning.

If a student associates negative emotional experiences with school, then this can obviously have bad results, such as creating a school phobia.

For example, if a student is bullied at school they may learn to associate the school with fear. It could also explain why some students show a particular dislike of certain subjects that continue throughout their academic career. This could happen if a student is humiliated or punished in class by a teacher.

Principles of Classical Conditioning

Neutral stimulus.

In classical conditioning, a neutral stimulus (NS) is a stimulus that initially does not evoke a response until it is paired with the unconditioned stimulus.

For example, in Pavlov’s experiment, the bell was the neutral stimulus, and only produced a response when paired with food.

Unconditioned Stimulus

Unconditioned response.

In classical conditioning, an unconditioned response is an innate response that occurs automatically when the unconditioned stimulus is presented.

Pavlov showed the existence of the unconditioned response by presenting a dog with a bowl of food and measuring its salivary secretions.

Conditioned Stimulus

Conditioned response.

In classical conditioning, the conditioned response (CR) is the learned response to the previously neutral stimulus.

In Ivan Pavlov’s experiments in classical conditioning, the dog’s salivation was the conditioned response to the sound of a bell.

Acquisition

The process of pairing a neutral stimulus with an unconditioned stimulus to produce a conditioned response.

In the initial learning period, acquisition describes when an organism learns to connect a neutral stimulus and an unconditioned stimulus.

In psychology, extinction refers to the gradual weakening of a conditioned response by breaking the association between the conditioned and the unconditioned stimuli.

The weakening of a conditioned response occurs when the conditioned stimulus is repeatedly presented without the unconditioned stimulus.

For example, when the bell repeatedly rang, and no food was presented, Pavlov’s dog gradually stopped salivating at the sound of the bell.

Spontaneous Recovery

Spontaneous recovery is a phenomenon of Pavlovian conditioning that refers to the return of a conditioned response (in a weaker form) after a period of time following extinction.

It is the reappearance of an extinguished conditioned response after a rest period when the conditioned stimulus is presented alone.

For example, when Pavlov waited a few days after extinguishing the conditioned response, and then rang the bell once more, the dog salivated again.

Generalization

In psychology, generalization is the tendency to respond in the same way to stimuli similar (but not identical) to the original conditioned stimulus.

For example, in Pavlov’s experiment, if a dog is conditioned to salivate to the sound of a bell, it may later salivate to a higher-pitched bell.

Discrimination

In classical conditioning, discrimination is a process through which individuals learn to differentiate among similar stimuli and respond appropriately to each one.

For example, eventually, Pavlov’s dog learns the difference between the sound of the 2 bells and no longer salivates at the sound of the non-food bell.

Higher-Order Conditioning

Higher-order conditioning is when a conditioned stimulus is paired with a new neutral stimulus to create a second conditioned stimulus. For example, a bell (CS1) is paired with food (UCS) so that the bell elicits salivation (CR). Then, a light (NS) is paired with the bell.

Eventually, the light alone will elicit salivation, even without the presence of food. This demonstrates higher-order conditioning, where the conditioned stimulus (bell) serves as an unconditioned stimulus to condition a new stimulus (light).

Critical Evaluation

Practical applications.

The principles of classical conditioning have been widely and effectively applied in fields like behavioral therapy, education, and advertising. Therapies like systematic desensitization use classical conditioning to help eliminate phobias and anxiety.

The behaviorist approach has been used in the treatment of phobias, and systematic desensitization . The individual with the phobia is taught relaxation techniques and then makes a hierarchy of fear from the least frightening to the most frightening features of the phobic object.

He then is presented with the stimuli in that order and learns to associate (classical conditioning) the stimuli with a relaxation response. This is counter-conditioning.

Explaining involuntary behaviors

Classical conditioning helps explain some reflexive or involuntary behaviors like phobias, emotional reactions, and physiological responses. The model shows how these can be acquired through experience.

The process of classical conditioning can probably account for aspects of certain other mental disorders. For example, in post-traumatic stress disorder (PTSD), sufferers tend to show classically conditioned responses to stimuli present at the time of the traumatizing event (Charney et al., 1993).

However, since not everyone exposed to the traumatic event develops PTSD, other factors must be involved, such as individual differences in people’s appraisal of events as stressors and the recovery environment, such as family and support groups.

Supported by substantial experimental evidence

There is a wealth of experimental support for basic phenomena like acquisition, extinction, generalization, and discrimination. Pavlov’s original experiments on dogs and subsequent studies have demonstrated classical conditioning in animals and humans.

There have been many laboratory demonstrations of human participants acquiring behavior through classical conditioning. It is relatively easy to classically condition and extinguish conditioned responses, such as the eye-blink and galvanic skin responses.

A strength of classical conditioning theory is that it is scientific . This is because it’s based on empirical evidence carried out by controlled experiments . For example, Pavlov (1902) showed how classical conditioning could be used to make a dog salivate to the sound of a bell.

Supporters of a reductionist approach say that it is scientific. Breaking complicated behaviors down into small parts means that they can be scientifically tested. However, some would argue that the reductionist view lacks validity . Thus, while reductionism is useful, it can lead to incomplete explanations.

Ignores biological predispositions

Organisms are biologically prepared to associate certain stimuli over others. However, classical conditioning does not sufficiently account for innate predispositions and biases.

Classical conditioning emphasizes the importance of learning from the environment, and supports nurture over nature.

However, it is limiting to describe behavior solely in terms of either nature or nurture , and attempts to do this underestimate the complexity of human behavior. It is more likely that behavior is due to an interaction between nature (biology) and nurture (environment).

Lacks explanatory power

Classical conditioning provides limited insight into the cognitive processes underlying the associations it describes.

However, applying classical conditioning to our understanding of higher mental functions, such as memory, thinking, reasoning, or problem-solving, has proved more problematic.

Even behavior therapy, one of the more successful applications of conditioning principles to human behavior, has given way to cognitive–behavior therapy (Mackintosh, 1995).

Questionable ecological validity

While lab studies support classical conditioning, some question how well it holds up in natural settings. There is debate about how automatic and inevitable classical conditioning is outside the lab.

In normal adults, the conditioning process can be overridden by instructions: simply telling participants that the unconditioned stimulus will not occur causes an instant loss of the conditioned response, which would otherwise extinguish only slowly (Davey, 1983).

Most participants in an experiment are aware of the experimenter’s contingencies (the relationship between stimuli and responses) and, in the absence of such awareness often fail to show evidence of conditioning (Brewer, 1974).

Evidence indicates that for humans to exhibit classical conditioning, they need to be consciously aware of the connection between the conditioned stimulus (CS) and the unconditioned stimulus (US). This contradicts traditional theories that humans have two separate learning systems – one conscious and one unconscious – that allow conditioning to occur without conscious awareness (Lovibond & Shanks, 2002).

There are also important differences between very young children or those with severe learning difficulties and older children and adults regarding their behavior in a variety of operant conditioning and discrimination learning experiments.

These seem largely attributable to language development (Dugdale & Lowe, 1990). This suggests that people have rather more efficient, language-based forms of learning at their disposal than just the laborious formation of associations between a conditioned stimulus and an unconditioned stimulus.

Ethical concerns

The principles of classical conditioning raise ethical concerns about manipulating behavior without consent. This is especially true in advertising and politics.

• Manipulation of preferences – Classical conditioning can create positive associations with certain brands, products, or political candidates. This can manipulate preferences outside of a person’s rational thought process.
• Encouraging impulsive behaviors – Conditioning techniques may encourage behaviors like impulsive shopping, unhealthy eating, or risky financial choices by forging positive associations with these behaviors.
• Preying on vulnerabilities – Advertisers or political campaigns may exploit conditioning techniques to target and influence vulnerable demographic groups like youth, seniors, or those with mental health conditions.
• Reduction of human agency – At an extreme, the use of classical conditioning techniques reduces human beings to automata reacting predictably to stimuli. This is ethically problematic.

Deterministic theory

A final criticism of classical conditioning theory is that it is deterministic . This means it does not allow the individual any degree of free will. Accordingly, a person has no control over the reactions they have learned from classical conditioning, such as a phobia.

The deterministic approach also has important implications for psychology as a science. Scientists are interested in discovering laws that can be used to predict events.

However, by creating general laws of behavior, deterministic psychology underestimates the uniqueness of human beings and their freedom to choose their destiny.

The Role of Nature in Classical Conditioning

Behaviorists argue all learning is driven by experience, not nature. Classical conditioning exemplifies environmental influence. However, our evolutionary history predisposes us to learn some associations more readily than others. So nature also plays a role.

For example, PTSD develops in part due to strong conditioning during traumatic events. The emotions experienced during trauma lead to neural activity in the amygdala , creating strong associative learning between conditioned and unconditioned stimuli (Milad et al., 2009).

Individuals with PTSD show enhanced fear conditioning, reflected in greater amygdala reactivity to conditioned threat cues compared to trauma-exposed controls. In addition to strong initial conditioning, PTSD patients exhibit slower extinction to conditioned fear stimuli.

During extinction recall tests, PTSD patients fail to show differential skin conductance responses to extinguished versus non-extinguished cues, indicating impaired retention of fear extinction. Deficient extinction retention corresponds to reduced activation in the ventromedial prefrontal cortex and hippocampus and heightened dorsal anterior cingulate cortex response during extinction recall in PTSD patients.

In influential research on food conditioning, John Garcia found that rats easily learned to associate a taste with nausea from drugs, even if illness occurred hours later.

However, conditioning nausea to a sight or sound was much harder. This showed that conditioning does not occur equally for any stimulus pairing. Rather, evolution prepares organisms to learn some associations that aid survival more easily, like linking smells to illness.

The evolutionary significance of taste and nutrition ensures robust and resilient classical conditioning of flavor preferences, making them difficult to reverse (Hall, 2002).

Forming strong and lasting associations between flavors and nutrition aids survival by promoting the consumption of calorie-rich foods. This makes flavor conditioning very robust.

Repeated flavor-nutrition pairings in these studies lead to overlearning of the association, making it more resistant to extinction.

The learning is overtrained, context-specific, and subject to recovery effects that maintain the conditioned behavior despite extinction training.

Classical vs. operant condioning

In summary, classical conditioning is about passive stimulus-response associations, while operant conditioning is about actively connecting behaviors to consequences. Classical works on reflexes and operant on voluntary actions.

• Stimuli vs consequences : Classical conditioning focuses on associating two stimuli together. For example, pairing a bell (neutral stimulus) with food (reflex-eliciting stimulus) creates a conditioned response of salivation to the bell. Operant conditioning is about connecting behaviors with the consequences that follow. If a behavior is reinforced, it will increase. If it’s punished, it will decrease.
• Passive vs. active : In classical conditioning, the organism is passive and automatically responds to the conditioned stimulus. Operant conditioning requires the organism to perform a behavior that then gets reinforced or punished actively. The organism operates on the environment.
• Involuntary vs. voluntary : Classical conditioning works with involuntary, reflexive responses like salivation, blinking, etc. Operant conditioning shapes voluntary behaviors that are controlled by the organism, like pressing a lever.
• Association vs. reinforcement : Classical conditioning relies on associating stimuli in order to create a conditioned response. Operant conditioning depends on using reinforcement and punishment to increase or decrease voluntary behaviors.

Learning Check

• In Ivan Pavlov’s famous experiment, he rang a bell before presenting food powder to dogs. Eventually, the dogs salivated at the mere sound of the bell. Identify the neutral stimulus, unconditioned stimulus, unconditioned response, conditioned stimulus, and conditioned response in Pavlov’s experiment.
• A student loves going out for pizza and beer with friends on Fridays after class. Whenever one friend texts the group about Friday plans, the student immediately feels happy and excited. The friend starts texting the group on Thursdays when she wants the student to feel happier. Explain how this is an example of classical conditioning. Identify the UCS, UCR, CS, and CR.
• A college student is traumatized after a car accident. She now feels fear every time she gets into a car. How could extinction be used to eliminate this acquired fear?
• A professor always slams their book on the lectern right before giving a pop quiz. Students now feel anxiety whenever they hear the book slam. Is this classical conditioning? If so, identify the NS, UCS, UCR, CS, and CR.
• Contrast classical conditioning and operant conditioning. How are they similar and different? Provide an original example of each type of conditioning.
• How could the principles of classical conditioning be applied to help students overcome test anxiety?
• Explain how taste aversion learning is an adaptive form of classical conditioning. Provide an original example.
• What is second-order conditioning? Give an example and identify the stimuli and responses.
• What is the role of extinction in classical conditioning? How could extinction be used in cognitive behavioral therapy for anxiety disorders?

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Pavlov’s Dog: The Psychology Experiment That Changed Everything

Pavlov’s Dog is a well-known experiment in psychology that has been taught for decades. Ivan Pavlov , a Russian physiologist, discovered classical conditioning through his experiments with dogs. He found that dogs could be trained to associate a sound with food, causing them to salivate at the sound alone.

The experiment began with Pavlov ringing a bell every time he fed his dogs. After a while, the dogs began to associate the sound of the bell with food and would salivate at the sound alone, even if no food was present. This became known as a conditioned response, where a previously neutral stimulus (the bell) became associated with a natural response (salivating).

The experiment has been used to explain many psychological phenomena, including addiction, phobias, and anxiety. It has also been applied in therapy, where patients can learn to associate positive experiences with previously negative stimuli. The Pavlov’s Dog experiment is a crucial part of psychology’s history and continues to be studied today.

Pavlov’s Life and Career

Ivan Pavlov was a Russian physiologist who lived from 1849 to 1936. He is best known for his work in classical conditioning, a type of learning that occurs when a neutral stimulus is consistently paired with a stimulus that elicits a response. Pavlov was born in Ryazan, Russia, and studied at the University of St. Petersburg, where he received his doctorate in 1879.

Pavlov’s early research focused on the digestive system, and he discovered that the secretion of gastric juice was not a passive process but rather a response to stimuli. This led him to develop the concept of the conditioned reflex, which he explored in detail in his famous experiments with dogs.

In these experiments, Pavlov trained dogs to associate the sound of a bell with food presentation. Over time, the dogs began to salivate at the sound of the bell, even when no food was present. This demonstrated that a neutral stimulus (the bell) could become associated with a natural response (salivation) through repeated pairings with a stimulus that elicits that response (food).

Pavlov’s work had a profound impact on the field of psychology, and his ideas continue to influence research today. He was awarded the Nobel Prize in Physiology or Medicine in 1904 for his work on the physiology of digestion. Still, his legacy is best remembered for his contributions to the study of learning and behavior.

Classical Conditioning

Classical conditioning is a type of learning that occurs when a neutral stimulus is repeatedly paired with a stimulus that naturally elicits a response. Over time, the neutral stimulus becomes associated with the natural stimulus and begins to produce the same response. Russian physiologist Ivan Pavlov first studied this type of learning in the late 1800s.

One of the most famous examples of classical conditioning is Pavlov’s experiment with dogs. In this experiment, Pavlov rang a bell every time he fed the dogs. Eventually, the dogs began to salivate at the sound of the bell, even when no food was present. The sound of the bell had become associated with the food, and the dogs had learned to associate the two stimuli.

Classical conditioning can be used to explain a variety of behaviors and responses. For example, a person who has been in a car accident may develop a fear of driving. The sound of screeching tires or the sight of a car may become associated with the traumatic experience, causing the person to feel anxious or fearful when driving.

Classical conditioning can also be used to treat certain types of phobias and anxiety disorders. By gradually exposing a person to the feared stimulus in a safe and controlled environment, the person can learn to associate the stimulus with safety and relaxation rather than fear and anxiety.

Classical conditioning is a powerful tool for understanding how we learn and respond to environmental stimuli. By understanding the principles of classical conditioning, we can better understand our behaviors and emotions, as well as those of others around us.

Pavlov’s Experiments

Pavlov’s experiments with dogs revolutionized the field of psychology and laid the foundation for the study of classical conditioning. In this section, we will explore two aspects of his experiments: salivating dogs and conditioned responses.

Salivating Dogs

Pavlov observed that dogs would salivate when presented with food. However, he also noticed that the dogs would start salivating before the food was presented. This led him to hypothesize that the dogs were responding not just to the food but to other associated stimuli, such as the sound of the food being prepared or the sight of the person who fed them.

To test his hypothesis, Pavlov began a series of experiments where he would ring a bell before presenting the dogs with food. After a few repetitions, the dogs began to salivate at the sound of the bell alone, even when no food was present. This demonstrated that the dogs had learned to associate the sound of the bell with the presence of food and were responding accordingly.

Conditioned Response

Pavlov’s experiments with dogs led to the discovery of the conditioned response, the learned response to a previously neutral stimulus. In the case of Pavlov’s dogs, the sound of the bell was originally a neutral stimulus. Still, it became associated with food and, therefore, elicited a response (salivation) from the dogs.

The conditioned response is an essential concept in psychology, as it helps to explain how we learn to respond to various stimuli in our environment. For example, if we have a positive experience with a particular food, we may develop a conditioned response to the sight or smell of that food, even if we are not hungry.

Pavlov’s experiments with dogs were groundbreaking in psychology and led to the discovery of classical conditioning and the conditioned response. By demonstrating that animals (and humans) can learn to respond to previously neutral stimuli, Pavlov paved the way for further research into the mechanisms of learning and behavior.

Significance in Psychology

Pavlov’s dog experiment has been a significant discovery in psychology. It has paved the way for developing various theories and has been instrumental in understanding human behavior. In this section, we will discuss the significance of Pavlov’s dog experiment in the context of behaviorism and learning theories.

Behaviorism

Pavlov’s dog experiment has been a cornerstone in the development of behaviorism. Behaviorism is a school of thought in psychology that emphasizes the importance of observable behavior rather than internal mental states. Pavlov’s experiment demonstrated how a stimulus-response connection could be formed through conditioning. This concept has been used to explain various behaviors, such as phobias and addictions.

Learning Theories

Pavlov’s dog experiment has also been significant in developing learning theories . Learning theories are concerned with how people acquire new knowledge and skills. Pavlov’s experiment demonstrated how classical conditioning could teach animals new behaviors. This concept has been used to explain various learning phenomena, such as the acquisition of language and the development of social skills.

In conclusion, Pavlov’s dog experiment has been a significant discovery in psychology. It has been instrumental in the development of behaviorism and learning theories. By understanding the principles of classical conditioning, we can better understand human behavior and how we learn new skills and behaviors.

Implications in Modern Psychology

Pavlov’s dog experiments have had a significant impact on modern psychology. His theory of classical conditioning has become a cornerstone of behaviorism, a school of thought that dominated psychology in the early 20th century. Today, it continues to influence psychologists and researchers in various fields.

One of the most significant implications of Pavlov’s work is the understanding of how learning takes place. His experiments showed that animals, including humans, can learn through association. This concept has been applied in many areas of modern psychology, including education, advertising, and even politics.

For example, in education, classical conditioning can improve students’ learning by associating positive experiences with specific subjects or activities. In advertising, classical conditioning can create positive associations between a product and a particular emotion or experience, influencing consumers’ purchasing decisions.

Moreover, Pavlov’s work has also contributed to developing other learning theories, such as operant conditioning, which focuses on the consequences of behavior rather than the stimuli that precede it. These theories have been used to explain various human behaviors, from addiction to language acquisition.

Pavlov’s dog experiments have had a lasting impact on modern psychology. His theory of classical conditioning has contributed to our understanding of how learning takes place and has been applied in various fields, from education to advertising. His work has also influenced the development of other learning theories, making it a crucial part of studying human behavior.

Criticism and Controversies

While Pavlov’s experiments have been foundational in psychology, they have also been subject to criticism and controversy. Here are a few examples:

• Animal cruelty:  Some critics argue that Pavlov’s experiments on dogs were cruel and unethical. The dogs were often subjected to painful surgeries and kept in small cages for long periods. While these practices were common in the early 20th century, they would not be acceptable by today’s ethical standards.
• Oversimplification of behavior:  Pavlov’s experiments focused on classical conditioning, which suggests that behavior is determined solely by external stimuli. However, this oversimplifies the complex nature of human behavior, which is influenced by various factors, including genetics, environment, and personal experience.
• Limited generalizability:  Pavlov’s experiments were conducted on dogs, which may not accurately reflect human behavior. While some of the principles of classical conditioning may apply to humans, it is essential to recognize that there are also significant differences between species.
• Misinterpretation of results:  Pavlov’s work has been subject to misinterpretation over the years. For example, many people believe that Pavlov’s dogs learned to salivate at the sound of a bell because they associated it with food. However, this is only partially accurate. The dogs learned to associate the sound of the bell with the experimenter’s presence, who would then provide the food.

Frequently Asked Questions

What were the basic features of classical conditioning discovered by pavlov.

Classical conditioning is a type of learning in which a neutral stimulus becomes associated with a meaningful stimulus, resulting in a behavioral response. Pavlov discovered that when a neutral stimulus (such as a bell) was repeatedly paired with a meaningful stimulus (such as food), the neutral stimulus alone could elicit the same response (such as salivation) as the meaningful stimulus.

What was the purpose of Pavlov’s dog experiment?

Pavlov’s dog experiment was designed to study the process of classical conditioning. He wanted to understand how dogs learn to associate a neutral stimulus (such as a bell) with a meaningful stimulus (such as food) and how this association leads to a behavioral response (such as salivation).

How did Pavlov’s experiments contribute to the development of psychology?

Pavlov’s experiments were groundbreaking in the field of psychology. They provided evidence for the concept of classical conditioning, which has since been used to explain a wide range of human and animal behaviors. Pavlov’s work also paved the way for the development of behaviorism, a school of psychology that emphasizes the importance of observable behavior in understanding human and animal psychology.

What is the Pavlovian response and how does it work?

The Pavlovian response is a learned response to a previously neutral stimulus. It works by pairing the neutral stimulus with a meaningful stimulus, which leads to the formation of an association between the two. Once the association is formed, the neutral stimulus alone can elicit the same response as the meaningful stimulus.

How is Pavlovian conditioning used in dog training?

Pavlovian conditioning is often used in dog training to teach dogs new behaviors or to modify existing ones. For example, a trainer might use a clicker (a neutral stimulus) to signal to a dog that it has performed a desired behavior (a meaningful stimulus), and then reward the dog with a treat. Over time, the dog will learn to associate the clicker with the reward and will perform the desired behavior without the need for a treat.

What is the Pavlovian response in humans and how is it studied?

The Pavlovian response in humans is similar to that in dogs: it involves the formation of an association between a neutral stimulus and a meaningful stimulus, resulting in a learned response. This response has been studied in a variety of contexts, including addiction, phobias, and taste aversions. Researchers use a variety of methods to study the Pavlovian response in humans, including brain imaging techniques and behavioral experiments.

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7.1 Learning by Association: Classical Conditioning

Learning objectives.

• Describe how Pavlov’s early work in classical conditioning influenced the understanding of learning.
• Review the concepts of classical conditioning, including unconditioned stimulus (US), conditioned stimulus (CS), unconditioned response (UR), and conditioned response (CR).
• Explain the roles that extinction, generalization, and discrimination play in conditioned learning.

Pavlov Demonstrates Conditioning in Dogs

In the early part of the 20th century, Russian physiologist Ivan Pavlov (1849–1936) was studying the digestive system of dogs when he noticed an interesting behavioral phenomenon: The dogs began to salivate when the lab technicians who normally fed them entered the room, even though the dogs had not yet received any food. Pavlov realized that the dogs were salivating because they knew that they were about to be fed; the dogs had begun to associate the arrival of the technicians with the food that soon followed their appearance in the room.

Figure 7.2 Ivan Pavlov

Ivan Pavlov’s research made substantial contributions to our understanding of learning.

LIFE Photo Archive – Wikimedia Commons – public domain.

With his team of researchers, Pavlov began studying this process in more detail. He conducted a series of experiments in which, over a number of trials, dogs were exposed to a sound immediately before receiving food. He systematically controlled the onset of the sound and the timing of the delivery of the food, and recorded the amount of the dogs’ salivation. Initially the dogs salivated only when they saw or smelled the food, but after several pairings of the sound and the food, the dogs began to salivate as soon as they heard the sound. The animals had learned to associate the sound with the food that followed.

Pavlov had identified a fundamental associative learning process called classical conditioning . Classical conditioning refers to learning that occurs when a neutral stimulus (e.g., a tone) becomes associated with a stimulus (e.g., food) that naturally produces a behavior . After the association is learned, the previously neutral stimulus is sufficient to produce the behavior.

As you can see in Figure 7.3 “4-Panel Image of Whistle and Dog” , psychologists use specific terms to identify the stimuli and the responses in classical conditioning. The unconditioned stimulus (US) is something (such as food) that triggers a natural occurring response , and the unconditioned response (UR) is the naturally occurring response (such as salivation) that follows the unconditioned stimulus . The conditioned stimulus (CS) is a neutral stimulus that, after being repeatedly presented prior to the unconditioned stimulus, evokes a similar response as the unconditioned stimulus . In Pavlov’s experiment, the sound of the tone served as the conditioned stimulus that, after learning, produced the conditioned response (CR) , which is the acquired response to the formerly neutral stimulus . Note that the UR and the CR are the same behavior—in this case salivation—but they are given different names because they are produced by different stimuli (the US and the CS, respectively).

Figure 7.3 4-Panel Image of Whistle and Dog

Top left: Before conditioning, the unconditioned stimulus (US) naturally produces the unconditioned response (UR). Top right: Before conditioning, the neutral stimulus (the whistle) does not produce the salivation response. Bottom left: The unconditioned stimulus (US), in this case the food, is repeatedly presented immediately after the neutral stimulus. Bottom right: After learning, the neutral stimulus (now known as the conditioned stimulus or CS), is sufficient to produce the conditioned responses (CR).

Conditioning is evolutionarily beneficial because it allows organisms to develop expectations that help them prepare for both good and bad events. Imagine, for instance, that an animal first smells a new food, eats it, and then gets sick. If the animal can learn to associate the smell (CS) with the food (US), then it will quickly learn that the food creates the negative outcome, and not eat it the next time.

The Persistence and Extinction of Conditioning

After he had demonstrated that learning could occur through association, Pavlov moved on to study the variables that influenced the strength and the persistence of conditioning. In some studies, after the conditioning had taken place, Pavlov presented the sound repeatedly but without presenting the food afterward. Figure 7.4 “Acquisition, Extinction, and Spontaneous Recovery” shows what happened. As you can see, after the intial acquisition (learning) phase in which the conditioning occurred, when the CS was then presented alone, the behavior rapidly decreased—the dogs salivated less and less to the sound, and eventually the sound did not elicit salivation at all. Extinction refers to the reduction in responding that occurs when the conditioned stimulus is presented repeatedly without the unconditioned stimulus .

Figure 7.4 Acquisition, Extinction, and Spontaneous Recovery

Acquisition: The CS and the US are repeatedly paired together and behavior increases. Extinction: The CS is repeatedly presented alone, and the behavior slowly decreases. Spontaneous recovery: After a pause, when the CS is again presented alone, the behavior may again occur and then again show extinction.

Although at the end of the first extinction period the CS was no longer producing salivation, the effects of conditioning had not entirely disappeared. Pavlov found that, after a pause, sounding the tone again elicited salivation, although to a lesser extent than before extinction took place. The increase in responding to the CS following a pause after extinction is known as spontaneous recovery . When Pavlov again presented the CS alone, the behavior again showed extinction until it disappeared again.

Although the behavior has disappeared, extinction is never complete. If conditioning is again attempted, the animal will learn the new associations much faster than it did the first time.

Pavlov also experimented with presenting new stimuli that were similar, but not identical to, the original conditioned stimulus. For instance, if the dog had been conditioned to being scratched before the food arrived, the stimulus would be changed to being rubbed rather than scratched. He found that the dogs also salivated upon experiencing the similar stimulus, a process known as generalization . Generalization refers to the tendency to respond to stimuli that resemble the original conditioned stimulus . The ability to generalize has important evolutionary significance. If we eat some red berries and they make us sick, it would be a good idea to think twice before we eat some purple berries. Although the berries are not exactly the same, they nevertheless are similar and may have the same negative properties.

Lewicki (1985) conducted research that demonstrated the influence of stimulus generalization and how quickly and easily it can happen. In his experiment, high school students first had a brief interaction with a female experimenter who had short hair and glasses. The study was set up so that the students had to ask the experimenter a question, and (according to random assignment) the experimenter responded either in a negative way or a neutral way toward the students. Then the students were told to go into a second room in which two experimenters were present, and to approach either one of them. However, the researchers arranged it so that one of the two experimenters looked a lot like the original experimenter, while the other one did not (she had longer hair and no glasses). The students were significantly more likely to avoid the experimenter who looked like the earlier experimenter when that experimenter had been negative to them than when she had treated them more neutrally. The participants showed stimulus generalization such that the new, similar-looking experimenter created the same negative response in the participants as had the experimenter in the prior session.

The flip side of generalization is discrimination — the tendency to respond differently to stimuli that are similar but not identical . Pavlov’s dogs quickly learned, for example, to salivate when they heard the specific tone that had preceded food, but not upon hearing similar tones that had never been associated with food. Discrimination is also useful—if we do try the purple berries, and if they do not make us sick, we will be able to make the distinction in the future. And we can learn that although the two people in our class, Courtney and Sarah, may look a lot alike, they are nevertheless different people with different personalities.

In some cases, an existing conditioned stimulus can serve as an unconditioned stimulus for a pairing with a new conditioned stimulus —a process known as second-order conditioning . In one of Pavlov’s studies, for instance, he first conditioned the dogs to salivate to a sound, and then repeatedly paired a new CS, a black square, with the sound. Eventually he found that the dogs would salivate at the sight of the black square alone, even though it had never been directly associated with the food. Secondary conditioners in everyday life include our attractions to things that stand for or remind us of something else, such as when we feel good on a Friday because it has become associated with the paycheck that we receive on that day, which itself is a conditioned stimulus for the pleasures that the paycheck buys us.

The Role of Nature in Classical Conditioning

As we have seen in Chapter 1 “Introducing Psychology” , scientists associated with the behavioralist school argued that all learning is driven by experience, and that nature plays no role. Classical conditioning, which is based on learning through experience, represents an example of the importance of the environment. But classical conditioning cannot be understood entirely in terms of experience. Nature also plays a part, as our evolutionary history has made us better able to learn some associations than others.

Clinical psychologists make use of classical conditioning to explain the learning of a phobia — a strong and irrational fear of a specific object, activity, or situation . For example, driving a car is a neutral event that would not normally elicit a fear response in most people. But if a person were to experience a panic attack in which he suddenly experienced strong negative emotions while driving, he may learn to associate driving with the panic response. The driving has become the CS that now creates the fear response.

Psychologists have also discovered that people do not develop phobias to just anything. Although people may in some cases develop a driving phobia, they are more likely to develop phobias toward objects (such as snakes, spiders, heights, and open spaces) that have been dangerous to people in the past. In modern life, it is rare for humans to be bitten by spiders or snakes, to fall from trees or buildings, or to be attacked by a predator in an open area. Being injured while riding in a car or being cut by a knife are much more likely. But in our evolutionary past, the potential of being bitten by snakes or spiders, falling out of a tree, or being trapped in an open space were important evolutionary concerns, and therefore humans are still evolutionarily prepared to learn these associations over others (Öhman & Mineka, 2001; LoBue & DeLoache, 2010).

Another evolutionarily important type of conditioning is conditioning related to food. In his important research on food conditioning, John Garcia and his colleagues (Garcia, Kimeldorf, & Koelling, 1955; Garcia, Ervin, & Koelling, 1966) attempted to condition rats by presenting either a taste, a sight, or a sound as a neutral stimulus before the rats were given drugs (the US) that made them nauseous. Garcia discovered that taste conditioning was extremely powerful—the rat learned to avoid the taste associated with illness, even if the illness occurred several hours later. But conditioning the behavioral response of nausea to a sight or a sound was much more difficult. These results contradicted the idea that conditioning occurs entirely as a result of environmental events, such that it would occur equally for any kind of unconditioned stimulus that followed any kind of conditioned stimulus. Rather, Garcia’s research showed that genetics matters—organisms are evolutionarily prepared to learn some associations more easily than others. You can see that the ability to associate smells with illness is an important survival mechanism, allowing the organism to quickly learn to avoid foods that are poisonous.

Classical conditioning has also been used to help explain the experience of posttraumatic stress disorder (PTSD), as in the case of P. K. Philips described in the chapter opener. PTSD is a severe anxiety disorder that can develop after exposure to a fearful event, such as the threat of death (American Psychiatric Association, 1994). PTSD occurs when the individual develops a strong association between the situational factors that surrounded the traumatic event (e.g., military uniforms or the sounds or smells of war) and the US (the fearful trauma itself). As a result of the conditioning, being exposed to, or even thinking about the situation in which the trauma occurred (the CS), becomes sufficient to produce the CR of severe anxiety (Keane, Zimering, & Caddell, 1985).

Posttraumatic stress disorder (PTSD) represents a case of classical conditioning to a severe trauma that does not easily become extinct. In this case the original fear response, experienced during combat, has become conditioned to a loud noise. When the person with PTSD hears a loud noise, she experiences a fear response even though she is now far from the site of the original trauma.

Marc Wathieu – Luigi Coppola – CC BY-NC 2.0.

PTSD develops because the emotions experienced during the event have produced neural activity in the amygdala and created strong conditioned learning. In addition to the strong conditioning that people with PTSD experience, they also show slower extinction in classical conditioning tasks (Milad et al., 2009). In short, people with PTSD have developed very strong associations with the events surrounding the trauma and are also slow to show extinction to the conditioned stimulus.

Key Takeaways

• In classical conditioning, a person or animal learns to associate a neutral stimulus (the conditioned stimulus, or CS) with a stimulus (the unconditioned stimulus, or US) that naturally produces a behavior (the unconditioned response, or UR). As a result of this association, the previously neutral stimulus comes to elicit the same response (the conditioned response, or CR).
• Extinction occurs when the CS is repeatedly presented without the US, and the CR eventually disappears, although it may reappear later in a process known as spontaneous recovery.
• Stimulus generalization occurs when a stimulus that is similar to an already-conditioned stimulus begins to produce the same response as the original stimulus does.
• Stimulus discrimination occurs when the organism learns to differentiate between the CS and other similar stimuli.
• In second-order conditioning, a neutral stimulus becomes a CS after being paired with a previously established CS.
• Some stimuli—response pairs, such as those between smell and food—are more easily conditioned than others because they have been particularly important in our evolutionary past.

Exercises and Critical Thinking

• A teacher places gold stars on the chalkboard when the students are quiet and attentive. Eventually, the students start becoming quiet and attentive whenever the teacher approaches the chalkboard. Can you explain the students’ behavior in terms of classical conditioning?
• Recall a time in your life, perhaps when you were a child, when your behaviors were influenced by classical conditioning. Describe in detail the nature of the unconditioned and conditioned stimuli and the response, using the appropriate psychological terms.
• If posttraumatic stress disorder (PTSD) is a type of classical conditioning, how might psychologists use the principles of classical conditioning to treat the disorder?

American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text rev.). Washington, DC: Author.

Garcia, J., Ervin, F. R., & Koelling, R. A. (1966). Learning with prolonged delay of reinforcement. Psychonomic Science, 5 (3), 121–122.

Garcia, J., Kimeldorf, D. J., & Koelling, R. A. (1955). Conditioned aversion to saccharin resulting from exposure to gamma radiation. Science, 122 , 157–158.

Keane, T. M., Zimering, R. T., & Caddell, J. M. (1985). A behavioral formulation of posttraumatic stress disorder in Vietnam veterans. The Behavior Therapist, 8 (1), 9–12.

Lewicki, P. (1985). Nonconscious biasing effects of single instances on subsequent judgments. Journal of Personality and Social Psychology, 48 , 563–574.

LoBue, V., & DeLoache, J. S. (2010). Superior detection of threat-relevant stimuli in infancy. Developmental Science, 13 (1), 221–228.

Milad, M. R., Pitman, R. K., Ellis, C. B., Gold, A. L., Shin, L. M., Lasko, N. B.,…Rauch, S. L. (2009). Neurobiological basis of failure to recall extinction memory in posttraumatic stress disorder. Biological Psychiatry, 66 (12), 1075–82.

Öhman, A., & Mineka, S. (2001). Fears, phobias, and preparedness: Toward an evolved module of fear and fear learning. Psychological Review, 108 (3), 483–522.

Introduction to Psychology Copyright © 2015 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Learn More Psychology

• Behavioral Psychology

Pavlov's Dogs and Classical Conditioning

How pavlov's experiments with dogs demonstrated that our behavior can be changed using conditioning..

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One of the most revealing studies in behavioral psychology was carried out by Russian physiologist Ivan Pavlov (1849-1936) in a series of experiments today referred to as 'Pavlov's Dogs'. His research would become renowned for demonstrating the way in classical conditioning (also referred to as Pavlovian conditioning ) could be used to cultivate a particular association between the occurrence of one event in the anticipation of another.

• Conditioning
• Stimulus-Response Theory
• Reductionism in Psychology
• What Factors Affect Classical Conditioning?
• Imprinting and Relationships

Pavlov's Dog Experiments

Pavlov came across classical conditioning unintentionally during his research into animals' gastric systems. Whilst measuring the salivation rates of dogs, he found that they would produce saliva when they heard or smelt food in anticipation of feeding. This is a normal reflex response which we would expect to happen as saliva plays a role in the digestion of food.

Did You Know?

Psychologist Edwin Twitmyer at the University of Pennsylvania in the U.S. discovered classical conditioning at approximately the same time as Pavlov was conducting his research ( Coon, 1982 ). 1 However, the two were unaware of each other's research in this case of simultaneous discovery , and Pavlov received credit for the findings.

However, the dogs also began to salivate when events occurred which would otherwise be unrelated to feeding. By playing sounds to the dogs prior to feeding them, Pavlov showed that they could be conditioned to unconsciously associate neutral, unrelated events with being fed 2 .

Experiment Procedure

Pavlov's dogs were each placed in an isolated environment and restrained in a harness, with a food bowl in front of them and a device was used to measure the rate at which their saliva glands made secretions. These measurements would then be recorded onto a revolving drum so that Pavlov could monitor salivation rates throughout the experiments.

He found that the dogs would begin to salivate when a door was opened for the researcher to feed them.

This response demonstrated the basic principle of classical conditioning . A neutral event, such as opening a door (a neutral stimulus , NS) could be associated with another event that followed - in this case, being fed (known as the unconditioned stimulus , UCS). This association could be created through repeating the neutral stimulus along with the unconditioned stimulus, which would become a conditioned stimulus , leading to a conditioned response : salivation.

Pavlov continued his research and tested a variety of other neutral stimuli which would otherwise be unlinked to the receipt of food. These included precise tones produced by a buzzer, the ticking of a metronome and electric shocks .

The dogs would demonstrate a similar association between these events and the food that followed.

NEUTRAL STIMULUS (NS, eg. tone) > UNCONDITIONED STIMULUS (UCS, eg. receiving food)

when repeated leads to:

CONDITIONED STIMULUS (CS, eg. tone) > CONDITIONED RESPONSE (CR, eg. salivation)

The implications for Pavlov's findings are significant as they can be applied to many animals, including humans.

For example, when you first saw someone holding a balloon and a pin close to it, you may have watched in anticipation as they burst the balloon. After this had happened multiple times, you would associate holding the pin to the balloon with the 'bang' that followed. Like Pavlov's dogs, classical conditioning was leading you to associate a neutral stimulus (the pin approaching a balloon) with bursting of the balloon, leading to a conditioned response (flinching, wincing or plugging one's ears) to this now conditioned stimulus.

• Craik & Lockhart (1972) Levels of Processing Theory

Let us look now at some of the nuances of Pavlov's findings in relation to classical conditioning.

'Unconditioning' through experimental extinction

Once an animal has been inadvertently conditioned to produce a response to a stimulus, can this association ever be broken?

Pavlov presented the dogs with a tone which they would come to associate with food. He then played the tone but did not follow that by rewarding the dogs with food.

After he made the sound without food numerous times, the dogs' produced less saliva as the conditioning underwent experimental extinction - a case of 'unlearning' the association.

When experimental extinction occurs, is the association permanently broken?

Pavlov's research would suggest that it remains but is inactive after extinction, and can be re-activated by reinstating, for example, the food reward, as it was given during the original conditioning. This phenomenon is known as spontaneous recovery .

Forward Conditioning vs Backward Conditioning

During conditioning, it is important that the neutral stimulus (NS) is presented before the unconditioned stimulus (UCS) in order for learning to take place. This forward conditioning is more likely to lead to a conditioned response than when the neutral stimulus is presented after the conditioned stimulus has been provided ( backward conditioning ).

In the case of Pavlov's dogs, the tone must be played to the subject prior to the food being provided. Making a sound after the dogs have been fed may not lead to a conditioned association being made between the events.

Carr and Freeman (1919) attempted both forward and backward conditioning in rats, between a buzzer sound and closed doors in a maze. They found backward conditioning to be ineffective when compared to forward conditioning. 4

Delay Conditioning vs Trace Conditioning

We may use forward conditioning in one of two forms:

Delay Conditioning - when the unconditioned stimulus is provided prior to and during the unconditioned stimulus - there is a period of overlap where the neutral and unconditioned stimulus are given simultaneously, e.g. a buzzer sound begins, and after 10 seconds, food is given whilst the buzzer continues.

Trace Conditioning - when there is a delay after the unconditioned stimulus has been provided before the unconditioned stimulus is presented to the subject, e.g. buzzer sounds for 10 seconds, stops and after 10 seconds of silence (the trace interval ), food is presented.

Discussing delay conditioning, Pavlov (1927) asserted that the longer the delay between the stimuli, the more delayed the response would be 5 .

Temporal Conditioning

So far, we have looked at conditioning in which a neutral stimulus is key to eliciting a desired response. However, if an unconditioned stimulus is provided at regular intervals, even without a preceding neutral stimulus, animals' sense of timing will enable conditioning to take place, and a response may occur in time with the intervals.

For example, in a study in which rats were fed at either random or regular intervals, Kirkpatrick and Church (2003) found that the subjects underwent temporal conditioning in the anticipation of food when they were fed at set intervals. 6

Generalisation

Pavlov noticed that once neutral stimulus had been associated with an unconditioned stimulus, the conditioned stimulus could vary and the dogs would still generate a similar response. For example, once specific tone of buzzer sound was associated with food, differing toned buzzer sounds would solicit a conditioned response.

Nonetheless, the closer the stimulus was to the original stimulus used in conditioning, the clearer the response would be. This correlation between stimulus accuracy and response is referred to as a generalisation gradient , and has been demonstrated in studies such as Meulders et al (2013) . 7

Modern Classical Conditioning

Pavlov's dog experiments are still discussed today and have influenced many later ideas in psychology. The U.S. psychologist John B. Watson was impressed by Pavlov's findings and reproduced classical conditioning in the Little Albert Experiment (Watson, 1920), in which a subject was unethically conditioned to associate furry stimuli such as rabbits with a loud noise, and subsequently developed a fear of rats. 8

• Behavioral Approach

The numerous studies following the experiments, which have demonstrated classical conditioning using a variety of methods, also show the replicability of Pavlov's research, helping it to be recognised as an important unconscious influence of human behavior. This has helped the theory to be recognised and applied in many real life situations, from training dogs to creating associations in today's product advertisements.

Continue Reading

• Coon, D.J. (1982). Eponymy, obscurity, Twitmyer, and Pavlov. Journal of the History of Behavioral Science . 18 (3). 255-62.
• Pavlov, I.P. (1927). Conditioned Reflexes: An investigation of the physiological activity of the cerebral cortex. Retrieved from http://psychclassics.yorku.ca/Pavlov/ .
• Craik, F.I.M. and Lockhart, R.S. (1972). Levels of Processing: A Framework for Memory Research. Journal of Verbal Learning and Visual Behavior . 11 (6). 671-684.
• Carr, H. and Freeman A. (1919). Time relationships in the formation of associations. Psychology Review . 26 (6). 335-353.
• Pavlov, I.P. (1927). Conditioned Reflexes: An investigation of the physiological activity of the cerebral cortex. Retrieved from http://psychclassics.yorku.ca/Pavlov/lecture6.htm .
• Kirkpatrick, K and Church, R.M. (2003). Tracking of the expected time to reinforcement in temporal conditioning processes. Learning & Behavior . 31 (1). 3-21.
• Meulders A, Vandebroek, N. Vervliet, B. and Vlaeyen, J.W.S. (2013). Generalization Gradients in Cued and Contextual Pain-Related Fear: An Experimental Study in Health Participants. Frontiers in Human Neuroscience , 7 (345). 1-12.
• Watson, J.B. and Rayner, R. (1920). Conditioned Emotional Reactions. Journal of Experimental Psychology . 3 (1). 1-14.
• Watson, J.B. (1913). Psychology as the Behaviorist Views It. Psychological Review . (Watson, 1913). 20 . 158-177.

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Classical Conditioning: How It Works and Examples

What Is Classical Conditioning?

Classical conditioning, also called Pavlovian conditioning or respondent conditioning, is learning through association. This behavioral learning method was first studied in the late 19th century by Russian physiologist Ivan Pavlov. 

Pavlov’s dog experiment

In the 1890s, Pavlov was experimenting with dogs, ringing a bell whenever they were fed. Over time, the dogs learned to associate a neutral stimulus (bell ringing) with a positive one (food). Pavlov also noticed that his dogs would often begin to salivate whenever they heard the footsteps of his assistant bringing them the food. This is called a conditioned response. Pavlov's experiment and its association between positive and neutral stimuli became the foundation of classical conditioning theory.

Eventually, Pavlov linked these behavioral associations to humans. He spent the remainder of his career studying the phenomenon.

Terms to Know

To understand how classical conditioning works, it's helpful to understand the following terms.

• Neutral stimulus. A stimulus is something that triggers a physical or behavioral change. A neutral stimulus produces no response. At first, Pavlov's dogs had no response to the bell.
• Unconditioned stimulus. This is what leads to an automatic response. In Pavlov’s experiment, it's the food.
• Unconditioned response . A normal process, like salivating when you smell food, is an unconditioned response.
• Conditioned stimulus. This is when a formerly neutral stimulus, like the bell in Pavlov's experiment, mimics an unconditioned response, as when the dogs began to associate the bell with food and salivate.
• Conditioned response. The learned behavior, such as relating the bell to food, is called a conditioned response.  

What Is Classical Conditioning Theory?

Classical conditioning theory says that behaviors are learned by connecting a neutral stimulus with a positive one, such as when Pavlov's dogs heard a bell (neutral) and expected food (positive).  

There are essentially three stages in classical conditioning:.

Before conditioning. Something in the environment triggers a natural response in the subject. During this stage, no new behavior has been learned yet. This stage also includes a neutral stimulus, which doesn't affect the subject. To create a response to a neutral stimulus, it must be linked to an unconditioned stimulus -- like the bell to food. 

During conditioning. This is the stage in which the subject starts to associate the neutral stimulus with the positive stimulus that caused the response during the first stage. In Pavlov's experiment, this stage involved ringing a bell when the dogs were fed. Over time, the dogs began to associate the bell with food.

For this to work, the neutral stimulus should come before the positive (unconditioned) stimulus. It creates a cue for what comes next. Doing this over and over makes the conditioning stick. But sometimes it only takes one time to make an association, such as a hangover after too much drinking. 

After conditioning. During the final stage of conditioning, the subject firmly associates the neutral stimulus with the unconditioned response. This creates a new behavior, or what's known as the conditioned response. If the link between the two weakens or breaks, this leads to what's called extinction. When Pavlov's dogs no longer got food after hearing the bell, they eventually stopped associating the bell with food.

What Is the Little Albert Experiment?

Considered one of the "most ethically dubious experiments ever conducted," the Little Albert experiment was developed by psychologists John B. Watson and Rosalie Rayner, who first applied Pavlov's classical conditioning principles to human behavior.

In 1920, Watson and Rayner began their behavioral learning experiment with a 9-month-old boy named Albert. They tested his reactions to various things in his environment, including a white rat, burning newspapers, and a hammer striking a 4-foot steel bar just behind Albert's head. Because the sound of the hammer frightened Albert, it became the unconditioned stimulus, and fear became the unconditioned response.

When Albert was 11 months old, he was presented with the white rat. When he tried to pet it, the pipe was struck with the hammer, causing him to feel fear. The researchers did this over the next few weeks and eventually Albert saw the rat and showed a fearful response. 

They reproduced these results with a rabbit, a dog, and several other stimuli that were previously neutral. At the end of the experiment, Albert showed a fear response for all of them.

Classical Conditioning vs. Operant Conditioning

Classical conditioning relies on associating one stimulus with another, such as the sound of a bell with food. Learning through operant conditioning relies on what comes after behaviors. These are the consequences that reinforce or punish behaviors.

In operant conditioning, either positive or negative reinforcement is used to affect whether a behavior is likely to happen again.  

When you give your dog a treat after they follow a command, that's positive reinforcement. It encourages them to repeat the behavior. When you yell (punishment) after your dog grabs food off the counter, that's punishment or negative reinforcement. Like classical conditioning, operant conditioning requires repetition for learning to take place. 

Classical Conditioning Principles

Classical conditioning includes several steps:

Acquisition. The point at which the neutral stimulus and unconditioned stimulus become linked. In other words, the dog learns to relate the sound of the bell with food.  

Extinction. Extinction breaks the conditioned bonds between the stimuli. If the dog no longer sees food after hearing the bell, it will gradually stop associating the bell with food.

Spontaneous recovery. If, after extinction, the conditioned stimulus and neutral stimulus again appear in relationship to one another, the conditioned response will return. After the extinction of the conditioned response in his dogs, Pavlov rang the bell before producing the food a few days later. His dogs began to salivate at the sound of the bell again.

Generalization. A conditioned response may be produced with stimuli that are similar but not the same. For example, if Pavlov's dogs heard a bell that rang at a lower pitch and still salivated, that's generalization.

Discrimination. Discrimination is the ability to understand that two or more stimuli are different from one another. In Pavlov's experiment, he later introduced the dogs to two bell sounds. Food appeared only after one. The dogs soon learned the difference. 

Classical Conditioning Examples

Classical conditioning isn't just related to food or fear. You see examples of this type of conditioning every day, though you may not know it or consciously think about it. Here are some examples of classical conditioning in daily life.

• Every time you put on your shoes, your dog gets excited and runs to the front door. Your dog associates you putting on shoes with a walk, or maybe going for a car ride.
• You always buy the same type of crackers for your baby's morning snack. When you pull the box of crackers out of the cupboard, your baby gets excited and reaches toward the box because they associate that box with snack time.
• A certain perfume reminds you of your late grandmother. After her passing, smelling that perfume or similar scents make you sad because of its association with your grandmother.
• Your demanding boss occasionally berates underperforming employees in his office. You feel nervous or agitated whenever your boss asks one of your co-workers into his office and closes the door because that's what he does whenever someone's in trouble.
• You listen to your favorite music when you exercise. You don't generally enjoy working out, but eventually, you begin to relate the positive feelings you get from your playlist to working out.
• Advertising. You see an ad showing a cold, wet can of soda while pumping your gas. You start feeling thirsty and think about running inside and buying this soft drink. 

Classical Conditioning Uses

Psychologists consider classical conditioning a key type of learning. It can create changes in mental and physical health, emotions, and drive. Its uses include: 

• Phobias. Repeated exposure to the object of a phobia, such as frequently flying when you're afraid of planes, can reduce fears.
• Drug use. Counselors often urge former addicts to stay away from people and places associated with their drug use.
• Classroom learning. Teachers might use classical conditioning to associate learning with positive emotions rather than negative ones like fear or shame.
• Pet training. Classical conditioning taught Pavlov's dogs what to expect after they heard the bell: food. Your dog also learns to positively associate actions like picking up a leash with going for a walk or going out to pee.
• Food aversions. We're born favoring certain tastes more than others (like sweet vs. bitter). If you eat something and become sick, you might learn to avoid the food and even feel sick at the sight of it. 
• PTSD  For people with posttraumatic stress disorder (PTSD) , classical conditioning may not cure their condition but contribute to it. PTSD is a type of anxiety that comes from associating certain triggers with fearful experiences. For example, loud noises may remind a veteran of the sounds of war. 

Criticisms of Classical Conditioning

Classical conditioning stresses outward learning over traits we're born with. Some criticisms of classical conditioning include:

• It fails to consider complex human actions like thinking, reason, and memory that produce learning, too. 
• It takes a long time to make the associations that create learning.
• It assumes a lack of free will -- that people have no control over their reactions to stimuli.

Classical conditioning is a type of learning by association. It takes several steps to associate a neutral stimulus with a positive outcome. Classical conditioning is used to treat psychological problems such as drug addiction and phobias. But it's also the basis for posttraumatic stress disorder (PTSD). Classical conditioning appears in everyday life in advertising and in our sensory associations with good and bad events. 

Classical Conditioning FAQs

• What is the simple definition of classical conditioning? Classical conditioning is learning through association.  
• What is an example of classical conditioning? Listening to your favorite music during workouts is an example of associating exercise with a positive neutral stimulus.  
• What are the five elements of classical conditioning?  Elements of classical conditioning include acquisition, extinction, spontaneous recovery, generalization, and discrimination.

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Ivan Pavlov (Biography + Experiments)

When most people think of Ivan Pavlov two thoughts readily come to mind. The first is Pavlov was an amazing psychologist. The second is he worked with dogs. But although Pavlov did some incredible work with dogs and made major contributions to the field of psychology, the truth is he was not a psychologist at all. So, who exactly was he?

Who Is Ivan Pavlov? 

Ivan Petrovich Pavlov was a Russian physiologist who is best known for discovering the concept of classical conditioning. He was born on September 14, 1849, in Ryazan, Russia. Pavlov won the Nobel Prize for Physiology or Medicine in 1904. He died in Leningrad on February 27, 1936.

His Early Years

Ivan Pavlov was the eldest child of Varvara Ivanovna Uspenskaya and Peter Dmitrievich Pavlov. He had ten siblings. Pavlov’s mother was a homemaker and his father was a Russian Orthodox priest at the village church. His grandfather also worked at the church as a sexton.

Pavlov was a good reader by the time he was seven years old. However, he was seriously hurt when he fell from a high wall during his childhood. His injuries caused him to spend most of his early years at home and in his family garden. During this part of his life, Pavlov grew to love nature, gardening, and working with his hands.

As the years passed, Pavlov’s body slowly began to heal. He was eleven years old when he started classes at the Ryazan church school.

What did Ivan Pavlov Study?

After Pavlov completed his classes at the local church school, he enrolled at the seminary in Ryazan. He was immediately impressed by his teachers’ desire to share religious knowledge with him. But despite growing up in a religious household, Pavlov struggled to accept religion. He soon began to wonder if studying theology was right for him.

While at the seminary Pavlov became inspired by the ideas of Dmitry Pisarev—a radical Russian writer and social critic, and Ivan M. Sechenov—a prominent Russian physiologist. Their progressive ideas convinced Pavlov to drop his religious studies at the seminary and devote his life to science. Unsurprisingly, Pavlov's father was furious when he found out. However, Pavlov was determined to live his life the way he wanted.

University of St. Petersburg

In 1870, Pavlov was accepted at the University of St. Petersburg. He enrolled in the physics and mathematics department because he wanted to study natural science. Pavlov spent much of his time studying chemistry and physiology. His first-year chemistry professor was Dmitri Mendeleev, the man who invented the periodic table of elements.

During his first research course in natural science, Pavlov and another student named Afanasyev published a research paper on the physiology of pancreatic nerves. They received much praise and were awarded a gold medal for their work. Overall, Pavlov's grades at the University of St. Petersburg were excellent. He completed his degree in natural science in 1875.

Pavlov's passion for physiology motivated him to continue his studies at the Imperial Academy of Medical Surgery. While there, he worked as an assistant to his former teacher Elias von Cyon—a Russian-French physiologist. However, von Cyon was forced to relocate to Paris when students protested his political views. When von Cyon was replaced by another instructor, Pavlov quit the department.

Pavlov spent two years as an assistant at the physiological department of the Veterinary Institute. During that time he worked on his medical dissertation on the circulatory system. In 1878, Pavlov was offered the position of director of the Physiological Laboratory at Sergey Botkin’s clinic. Botkin was a famous clinician and therapist at the time and was later regarded as one of the pillars of modern medical science in Russia.

Pavlov graduated from the Academy in 1879. At his graduation, he was awarded another gold medal for his outstanding research. He also won a fellowship at the Academy. This fellowship and his role at the Botkin Clinic allowed him to continue his research until he completed his dissertation on The Centrifugal Nerves of the Heart in 1883.

Work with Carl Ludwig

In 1884, Pavlov went abroad to continue his studies. First, he worked under the supervision of Carl Ludwig—a well known cardiovascular physiologist—in Leipzig, Germany. He then went to Breslau, Poland to assist renowned physiologist Rudolf Heidenhain in his study of digestion in dogs. After his studies were complete, Pavlov returned to Russia in 1886.

Pavlov accepted the role of professor of Pharmacology at the Military Medical Academy (formerly called the Imperial Academy of Medical Surgery) in 1890. Less than one year later, he was also invited to serve as the head of the Physiology Department at the Institute of Experimental Medicine. Pavlov was appointed to the Chair of Physiology at the Military Medical Academy in 1895—a role he occupied for 30 years. However, most of his research on the physiology of digestion was conducted at the Institute of Experimental Medicine, where he worked for 45 years.

Pavlov's Dog Experiment

The bulk of Pavlov’s research was conducted from 1891 to the early 1900s. In 1902 he was researching how dogs salivated in response to being fed. To measure the amount of saliva produced, he surgically implanted a small tube into the cheek of each dog. His prediction was that salivation would begin only after the food was placed in front of the dogs.

However, Pavlov soon noticed something quite interesting. At first, the dogs salivated only if they were presented with food. But later in the experiment, the dogs began salivating when they heard Pavlov’s assistant coming with their food. Were the dogs producing more saliva because they could smell the food as it was brought closer? Apparently not, because the dogs still salivated even when Pavlov’s assistant came empty-handed.

Pavlov was fascinated by these results. It did not take him long to figure out that other objects or events would trigger the same salivation response if the dogs associated those objects or events with food. Pavlov immediately realized he had made an important scientific discovery. He spent the rest of his professional life studying this type of learning.

Discovering Pavlovian Conditioning

Pavlovian conditioning (also called classical conditioning ) refers to the process of learning through association. It was first documented by Ivan Pavlov in 1902 when he was researching digestion in dogs. Although he was a brilliant man, Pavlov made this discovery quite by accident. Nevertheless, classical conditioning went on to have a major influence in the field of psychology.

Pavlovian conditioning assumes there are some behaviors that humans and animals do not need to learn. Instead, the response or reflex occurs naturally whenever it is triggered. In Pavlov’s case, the dogs salivated (unconditioned reflex) when they were presented with food (unconditioned stimulus). In this case, the stimulus and reflex are described as “unconditioned” because the reaction is hard-wired into the dogs and required no learning.

However, Pavlov knew that the dogs did learn new things as the experiment went on. He came to this conclusion because initially, the dogs only salivated when they were given food. At the start of the experiment they did not salivate when they heard the footsteps of his assistant. The fact that the dogs later started to salivate when they heard the footsteps shows they had learned to associate Pavlov’s assistant with the food they desired.

Stimuli in Classical Conditioning

Pavlov's lab assistant can be thought of as a “neutral stimulus” at the beginning of the experiment. This is because his presence caused no response from the dogs. As the experiment went on, the dogs linked the lab assistant (neutral stimulus) with food (unconditioned stimulus). After the association was formed, the dogs began salivating whenever they heard the assistant’s footsteps.

If the dogs could learn to associate his assistant with food, Pavlov believed they could learn to associate other things with food. To test if his belief was correct, he decided to use a metronome as his neutral stimulus. A metronome is a device that produces a click or tone at regular intervals.

Under normal circumstances, dogs do not salivate when they hear a tone. But if the tone was successfully linked with food, Pavlov believed the dogs would salivate each time they heard it.

How Did Pavlov's Dog Experiments Work? 

So Pavlov started to play the tone before he fed his dogs. He repeated the process for days. After some time had passed, he played the tone without presenting any food to the dogs. As he expected, his dogs showed an increase in salivation whenever they heard the tone.

Although the dogs had no response to the tone at the start of the experiment, they had learned a new response by the end of it. And as this response needed to be learned, Pavlov called it a “conditional reflex.” Pavlov also recognized that the tone was no longer a neutral stimulus. By linking it with food (unconditioned stimulus), the tone had become a “conditioned stimulus.”

There are many reports that Pavlov used a bell for the experiments he conducted with his dogs. And he may have used one on occasion. However, Pavlov wanted to control the intensity, quality, and duration of the stimuli. So he relied heavily on a metronome, harmonium, buzzer, and even electric shocks for most of his experiments.

There was one more thing Pavlov discovered during his experiment. He realized that the tone (initially a neutral stimulus) and the food (unconditioned stimulus) needed to be presented close together in time for the link to be made. He referred to this requirement as the law of temporal contiguity. If there is too much time between the playing of the tone and the presentation of the food, the dogs would not learn to salivate when they heard the tone.

Behaviorism Theory

Behaviorism is a theory that suggests human and animal psychology can be understood by studying observable actions. While many forms of psychology emphasize thoughts and feelings, behaviorists believe the “inner world” is not important because it cannot be seen or accurately measured. Behaviorists believe all human behavior is learned by interacting with the environment. Consequently, any person can be trained to become an expert in any task, regardless of his or her personality, culture, or genetic traits.

John B. Watson

Behaviorism was developed by American psychologist John B. Watson in 1913. He was greatly influenced by the work and observations of Ivan Pavlov. Watson believed all facets of human psychology could be explained by Pavlovian conditioning. He denied the existence of the mind, believed all humans begin as a blank slate, and claimed speech, emotional reactions, and other complex behaviors were nothing more than learned responses to environmental stimuli.

B.F. Skinner

Another prominent behaviorist who was heavily influenced by Pavlov is Burrhus Frederic Skinner . While Watson expanded on methodological behaviorism, Skinner pioneered a different approach called radical behaviorism. Skinner is widely considered to be the father of operant conditioning—a learning process that is different from classical conditioning. Skinner actually had plans to major in English and become a novelist before he was introduced to Pavlov’s work in 1927.

Although many people think Pavlov did not care about studying things that could not be measured, he never made those claims himself. In fact, he viewed the human mind as a great mystery. If scientists want to understand the human mind, the process has to begin somewhere. Pavlov believed the best approach was to begin with observation and hard data.

Pavlov's Impact on Psychology and Education

Classical conditioning has had a big impact on modern-day learning strategies. Although Pavlov worked with animals, he always believed the principles of classical conditioning can be applied to humans. A number of Pavlov’s basic ideas have been implemented in classrooms and other learning environments. Just as Pavlov used different stimuli to increase or decrease specific behaviors in his dogs, many teachers change their tools, instructions, or environment to influence the behavior of their students and increase learning.

If a teacher is faced with an ongoing problem behavior from a student, the teacher may try to eliminate or change the behavior. One way to do this is by changing something in the learning environment that triggers that specific behavior. So the teacher may move the student to a different seat, change the lights in the classroom, or close an open window if they trigger the bad behavior. The teacher may also try to change her content or modify the way it is presented in order to boost learning.

These strategies are particularly effective for teaching people with behavior problems or learning disabilities. They have been implemented in many schools, homes, and health centers around the world.

Ivan Pavlov's Accomplishments and Awards

Pavlov published many research papers and lectures throughout his long professional career. Some of his more notable works have been compiled into a few books such as The Work of the Digestive Glands (1897), Conditioned Reflexes (1926), and Psychopathology and Psychiatry (1961). His biography, Pavlov: A Biography was written by Boris Babkin and published in 1949. A more recent biography, Ivan Pavlov: A Russian Life in Science, was written by Daniel P. Todes and published in 2014.

Nobel Prize

Pavlov was nominated for the Nobel Prize from 1901 to 1904. However, he did not win the prize for the first three years because his nominations were tied to a variety of findings rather than a specific discovery. When he was first nominated in 1901, he was already well known among physiologists, especially those who studied digestion. However, Pavlov's research on conditioned reflexes was not published until 1902 and it may have taken a while for this work to penetrate the field of psychology.

In 1904, Pavlov was finally awarded the Nobel Prize for Physiology or Medicine. He received the award for his outstanding research on digestion in animals. This research involved removing a dog's esophagus and creating a fistula or tunnel in a dog’s throat so that if the dog ate, the food would not enter its stomach. Pavlov would then collect and test the different secretions along the dog’s digestive system.

Although Pavlov’s methods may seem extreme by today's standards, he always did his best to keep his dogs fed and healthy. He viewed them as very valuable for his work. When his dogs eventually died, he found effective ways to get more. He would take in strays or even pay thieves to steal dogs from other people.

After Pavlov won the Nobel Prize, he drew the attention of many other scientists from around the world. American psychologists, in particular, became more aware of his work and were more willing to test his findings on conditional reflex.

Personal Life and Death

Throughout his life, Pavlov was never easy to get along with. In his childhood days, he often felt uncomfortable around his parents. He was also known to be a volatile and difficult student. When he opened his lab as an adult, his staff knew to avoid him if he was having one of his many bad days.

Ivan Pavlov Children and Wife

Ivan Pavlov met Seraphima Vasilievna Karchevskaya (also known as Sara) in 1878 or 1879. At the time, Sara was a student at the Pedagogical Institute. It did not take long for the young couple to fall in love. They were married on May 1, 1881.

When Sara became pregnant for the first time, she had a miscarriage. The couple was very careful the second time Sara conceived, and she gave birth to a healthy baby boy named Mirchik. However, Mirchik died suddenly in childhood and this made Sara very depressed. Eventually, the couple had four more children. Their names were Vladimir, Victor, Vsevolod, and Vera.

Ivan and Sara Pavlov spent their first nine years as husband and wife in poverty. Due to their financial troubles, they were often forced to live in different homes so they could benefit from the hospitality of other people. Pavlov even grew potatoes and other crops outside his lab to help make ends meet. Once their finances became stable, Ivan and Sara were able to live together in the same house.

Pavlov was eventually able to earn money from health products he made in his lab. He sold the gastric juice he collected from his dogs as an effective treatment for indigestion. Of course, winning the Nobel Prize in 1904 brought monetary rewards. However, the ever-changing political scene in Russia made life difficult for him, his family, and his fellow scientists.

Cause of Death

On February 27, 1936, Ivan Pavlov passed away in Leningrad, Russia. He was 86 years old. He died from lung issues caused by pneumonia. Ever the researcher, Pavlov asked one of his students to sit beside his bed as he died so that the experience could be properly documented.

Related posts:

• The Little Albert Experiment
• Classical Conditioning (Memory Guide + Examples)
• Philip Zimbardo (Biography + Experiments)
• Albert Bandura (Biography + Experiments)
• Stimulus Response Theory (Thorndike's Research + Examples)

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Ivan Pavlov and the Theory of Classical Conditioning

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Classical conditioning.

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• Introduction

Learning is the process by which new knowledge, behaviors, attitudes, and ideas are acquired. Learning can occur through both unconscious and conscious pathways. Classical conditioning is one of those unconscious learning methods and is the most straightforward way in which humans can learn. Classical conditioning is the process in which an automatic, conditioned response is paired with specific stimuli. Although Edwin Twitmyer published findings pertaining to classical conditioning one year earlier, the best-known and most thorough work on classical conditioning is accredited to Ivan Pavlov, a Russian physiologist born in the mid-1800s. Pavlov had such a great impact on the study of classical conditioning that it is often referred to as Pavlovian conditioning. [1] [2] [3]

Pavlov’s Experiment

Classical conditioning was stumbled upon by accident. Pavlov was conducting research on the digestion of dogs when he noticed that the dogs’ physical reactions to food subtly changed over time. At first, the dogs would only salivate when the food was placed in front of them. However, later they salivated slightly before their food arrived. Pavlov realized that they were salivating at the noises that were consistently present before the food arrived; for example, the sound of a food cart is approaching.

To test his theory, Pavlov set up an experiment in which he rang a bell shortly before presenting food to the dogs. At first, the dogs elicited no response to the bells. However, eventually, the dogs began to salivate at the sound of the bell alone.

To understand classical conditioning, it is essential to be familiar with the following terms. A neutral stimulus is a stimulus that at first elicits no response. Pavlov introduced the ringing of the bell as a neutral stimulus. An unconditioned stimulus is a stimulus that leads to an automatic response. In Pavlov’s experiment, the food was the unconditioned stimulus. An unconditioned response is an automatic response to a stimulus. The dogs salivating for food is the unconditioned response in Pavlov’s experiment. A conditioned stimulus is a stimulus that can eventually trigger a conditioned response. In the described experiment, the conditioned stimulus was the ringing of the bell, and the conditioned response was salivation.

It is important to note that the neutral stimulus becomes the conditioned stimulus. Furthermore, it is important to realize that the unconditioned response and the conditioned response are the same except for which stimulus they are elicited by. In this case, salivation was the response, but the unconditioned response was triggered by food, whereas the conditioned response was triggered by the bell which indicated the coming of food.

Pavlov recorded several phenomena associated with classical conditioning. He found that the rate of acquisition, the initial stages of learning, depended on the noticeability of the stimulus and the time in between the introduction of the neutral stimulus and the unconditioned stimulus. In Pavlov’s experiment, this would translate to the time in between the bell ringing and the presentation of food. Second, Pavlov observed that the conditioned response was vulnerable to extinction. If the conditioned stimulus is continuously supplied in the absence of the unconditioned stimulus, then the conditioned response becomes weaker and weaker until it disappears. In Pavlov’s experiment, this would translate to Pavlov ringing the bell without giving food to the dogs. Eventually, the dogs would stop salivating at the sound of the bell. However, spontaneous recovery was also observed. Even if a substantial amount of time had passed, the conditioned response would easily recover if the neutral stimulus and the unconditioned stimulus were paired again. Lastly, he found that stimulus generalization and stimulus discrimination can occur. Stimulus generalization occurs when the dog can respond to stimuli that are similar to the conditioned stimulus. For example, if Pavlov’s dogs salivated at the sound of another ringing sound such as a cell phone ringing, that would be stimulus generalization. Stimulus discrimination, on the other hand, is being able to differentiate between similar stimuli and respond only to the correct stimuli. [4] [5] [6] [7]

• Issues of Concern

People can use classical conditioning to exploit others for their gain. A prominent example of this occurs in advertising. The advertiser generally attempts to get consumers to associate their product with a particular response or feeling so they are more likely to buy the product. Advertisers can use music or mouth-watering food in their ads to create an association with their product. These types of associations can lead to increased spending as well as poor eating habits especially if the product is unhealthy food. 

• Clinical Significance

Most psychologists now agree that classical conditioning is a basic form of learning. Furthermore, it is well-known that Pavlovian principles can influence human health, emotion, motivation, and therapy of psychological disorders. There are many clinically related uses of classical conditioning. For example, former drug users often have a craving when they are in a drug-related environment or around people that they associate with previous highs. Drug counselors often advise these people to stay away from settings that could trigger a desire to take drugs again. Also, it has been proven that classical conditioning can even affect the human immune system. When a particular taste accompanies a drug that influences an immune response, sometimes the taste itself can induce the immune response at a later time. Another example can be found in the overcoming of phobias. One patient, who had feared getting into an elevator for 30 years, forced herself to enter 20 elevators a day. After 10 days, her fear had almost completely vanished.

O.H Mowrer discovered that certain behaviors can be reconditioned when he successfully developed a therapy for bed-wetters. In his therapy, the child would sleep on a liquid-sensitive pad connected to an alarm. Once moisture was detected, the alarm would go off. After repetition, bladder relaxation became associated with waking up and 75% of the time, frequent bed-wetters were healed and longer wet the bed while they slept.

Another example of an effective therapy that is used to cure phobias is counterconditioning, which pairs the trigger stimulus with a response that is contrary to fear. Two counterconditioning techniques that have been proven to be effective are exposure therapy and aversive therapy. In general, exposure therapies are therapies that expose people to what scares them. Two types of exposure therapies are systematic desensitization and virtual reality exposure therapy. In systematic desensitization, a pleasant, relaxed state is associated with increasing anxiety-triggering stimuli. This therapy is common in the treatment of phobias. Virtual reality exposure follows the same concept as general exposure therapy but uses virtual reality to do instead of real-life situations. Aversive conditioning has the goal of substituting a negative response for a positive response to a harmful stimulus. This is essentially the reverse of systematic desensitization in which a positive response is replaced with a negative response to a harmless stimulus. One common example of aversive conditioning is mixing alcohol with an extremely bitter taste or lacing fingernails with something that causes severe nausea. The problem with this therapy is that patients can differentiate between situations inside and outside of the psychiatrist’s office. An alcoholic understands that if he drinks alcohol, it will normally not have that bitter taste. For this reason, a combination of conditioning therapies is the best approach to treat certain issues. [8] [9]

• Other Issues

A combination of both behavior modification therapy with medications can lead to better clinical outcomes than if either option is used alone. Some studies show enhanced outcomes when certain drugs are used in the psychological treatment of anxiety disorders and even post-traumatic stress disorders. Despite the clinical efficacy of these studies, it should be noted that each individual can have a different treatment plan that is optimal to only them. Some people might respond better to only therapy or medications rather than a combination of both. Furthermore, combination treatments can be more of a "mix and match" treatment where two patients can have similar amounts of treatment success but use different medications and therapy options. [10] [11] [12]

• Enhancing Healthcare Team Outcomes

Classical conditioning concepts are integrated into the design of health-related interventions (i.e. modeling, reinforcement, expectancies, and cues to action). Cohesiveness and consistency of the patient/ interprofessional team implementing these types of interventions are important factors for success. The interprofessional healthcare team consists of diagnosticians, medication experts, prescribers, and other members who tend to the everyday needs of the patient. Cohesiveness and communication become especially important for the extinguishing of addictive behaviors such as drug use, smoking, or drinking alcohol. Since relapse is always a possibility, proper protocols should be in place to help re-extinguish the behavior if necessary. However, these protocols mainly depend on the patient's honesty and willingness to seek out help. Additionally, the interprofessional team can increase conditioning success by involving the patient's friends and family. They not only provide emotional support for the patient but can also provide updates to the interprofessional team when needed. [13] [14]

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Disclosure: Ibraheem Rehman declares no relevant financial relationships with ineligible companies.

Disclosure: Navid Mahabadi declares no relevant financial relationships with ineligible companies.

Disclosure: Terrence Sanvictores declares no relevant financial relationships with ineligible companies.

Disclosure: Chaudhry Rehman declares no relevant financial relationships with ineligible companies.

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Ivan Pavlov and His Discovery of Classical Conditioning

• Classical Conditioning
• Contributions

Select Publications

Ivan Pavlov was a Russian physiologist best known in psychology for his discovery of classical conditioning. During his studies on the digestive systems of dogs, Pavlov noted that the animals salivated naturally upon the presentation of food.

However, he also noted that the animals began to salivate whenever they saw the white lab coat of an experimental assistant. It was through this observation that Pavlov discovered that by associating the presentation of food with the lab assistant, a conditioned response occurred. Pavlov was also able to demonstrate classical conditioning in his subjects by associating food with sound of a tone.

Learn more about Ivan Pavlov and his contributions to the field of psychology.

Pavlov discovered classical conditioning in the 1890s and published his results in 1897. The discovery had a reverberating influence on psychology. Pavlov's discovery had a major influence on other thinkers including John B. Watson and contributed significantly to the development of the school of thought known as behaviorism.

Take a closer look at Ivan Pavlov's life and career in this brief biography.

Ivan Pavlov is best known for:

• Classical conditioning
• Research on physiology and digestion
• 1904 Nobel Prize in Physiology

Ivan Petrovich Pavlov was born on September 14, 1849, in the village of Ryazan, Russia, where his father was the village priest. His earliest studies were focused on theology, but reading Charles Darwin's On the Origin of the Species had a powerful influence on his future interests.

He soon abandoned his religious studies and devoted himself to the study of science. In 1870, he began studying the natural sciences at St. Petersburg University.

Pavlov's primary interests were the study of physiology and natural sciences. He was a founder of the Russian Physiological Society and also served as its first president, a position he held for 19 years.  

"Science demands from a man all his life. If you had two lives that would not be enough for you. Be passionate in your work and in your searching, "  Pavlov once suggested.

So, how did his work in physiology lead to his discovery of classical conditioning?

Ivan Pavlov's Discovery of Classical Conditioning

While researching the digestive function of dogs, he noted his subjects would salivate when they saw the person who was delivering food. In a series of well-known experiments , he presented a variety of stimuli before the presentation of food, eventually finding that, after repeated association, a dog would salivate to the presence of a stimulus other than food.

Pavlov termed this response a conditional reflex . Pavlov also discovered that these reflexes originate in the cerebral cortex of the brain.

Pavlov received considerable acclaim for his work, including a 1901 appointment to the Russian Academy of Sciences and the 1904 Nobel Prize in Physiology. The Soviet government also offered substantial support for Pavlov's work, and the Soviet Union soon became a leading center of physiology research.

He died on February 27, 1936.

Ivan Pavlov's Contributions to Psychology

Many outside of psychology may be surprised to learn that Pavlov was not a psychologist at all. Not only was he not a psychologist; he reportedly was skeptical of the emerging field of psychology altogether.

However, his work had a major influence on the field, particularly on the development of behaviorism . His discovery and research on reflexes influenced the growing behaviorist movement, and his work was often cited in John B. Watson's writings.

Other researchers utilized Pavlov's work in the study of conditioning as a form of learning. His research also demonstrated techniques of studying reactions to the environment in an objective scientific method.

One of Pavlov's earliest publications was his 1897 text The Work of the Digestive Glands , which centered on his physiology research.

Later works that focused on his discovery of classical conditioning include his 1927 book Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex and Lectures on Conditioned Reflexes: Twenty-five Years of Objective Study of the High Nervous Activity (Behavior) of Animals which was published one year later.

A Word From Verywell

Ivan Pavlov may not have set out to change the face of psychology, but his work had a profound and lasting influence on the science of the mind and behavior. His discovery of classical conditioning helped establish the school of thought known as behaviorism.

Thanks to the work of behavioral thinkers such as Watson and Skinner, behaviorism rose to be a dominant force within psychology during the first half of the twentieth century. 

Brown RE, Molnár Z, Filaretova L, Ostrovsky M, Piccolino M, Lorusso L. The 100th anniversary of the Russian Pavlov Physiological Society. Physiology (Bethesda) . 2017;32(6):402-407. doi:10.1152/physiol.00023.2017

Eelen P. Classical conditioning: Classical yet modern . Psychol Belg . 2018;58(1):196-211. doi:10.5334/pb.451

McCabe B. Hopkins researcher discovers everything we know about Pavlov is wrong . Johns Hopkins Magazine . 2014.

Nobel. The Nobel Prize in Physiology or Medicine 1904: Ivan Pavlov - Biographical

Santana LH. Comparing Watson's behaviorism and Meyer's objectivism: Reassessing traditional assumptions in psychology . 2023.

Pavlov I. The work of the digestive glands . In: Scientific and Medical Knowledge Production, 1796-1918. Routledge. 2023:157-173

Schultz, D. P., & Schultz, S. E (Eds.). (2012). A History of Modern Psychology . Australia Belmont, CA: Thomson/Wadsworth.

Todes, DP. Ivan Pavlov: A Russian Life in Science . New York: Oxford; 2014.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Ivan Petrovich Pavlov

(1849-1936)

Who Was Ivan Petrovich Pavlov?

Ivan Pavlov abandoned his early theological schooling to study science. As the Department of Physiology head at the Institute of Experimental Medicine, his groundbreaking work on the digestive systems of dogs earned him the Nobel Prize for Physiology or Medicine in 1904. Pavlov remained an active researcher until his death on February 27, 1936.

Early Life and Education

Ivan Petrovich Pavlov was born on September 14, 1849, in Ryazan, Russia. The son of a priest, he attended a church school and theological seminary. However, he was inspired by the ideas of Charles Darwin and I.M. Sechenov, the father of Russian physiology, and gave up his theological studies in favor of scientific pursuit.

Pavlov studied chemistry and physiology at the University of St. Petersburg and received the degree of Candidate of Natural Sciences in 1875. He then enrolled at the Imperial Medical Academy in St. Petersburg, completing his graduate dissertation on the centrifugal nerves of the heart in 1883.

Discovery and Theory

After graduation, Pavlov studied under cardiovascular physiologist Carl Ludwig in Leipzig, Germany, and gastrointestinal physiologist Rudolf Heidenhain in Breslau, Poland. With Heidenhain, he devised an operation in which he created an exteriorized "pouch" on a dog's stomach and maintained nerve supply to properly study gastrointestinal secretions. He then spent two years at a laboratory in St. Petersburg, where he researched cardiac physiology and the regulation of blood pressure.

In 1890, Pavlov took charge of the Department of Physiology at the newly created Institute of Experimental Medicine. He was also named Professor of Pharmacology at the Imperial Medical Academy, and five years later was appointed to its vacant Chair of Physiology. During this period, Pavlov focused on the secretory activity of digestion in dogs, implanting fistulas in their salivary ducts to record the uninterrupted effects of the nervous system on the digestive process.

Pavlov's observations led him to formulate his concept of the conditioned reflex. In his most famous experiment, he sounded a tone just before presenting dogs with food, conditioning them to begin salivating every time he sounded the tone. Pavlov published his results in 1903, and delivered a presentation on "The Experimental Psychology and Psychopathology of Animals" at the 14th International Medical Congress in Madrid, Spain, later that year.

Nobel Prize and Achievements

For his groundbreaking work, Pavlov was named the 1904 Nobel Prize winner for Physiology or Medicine. More honors followed over the years. He was elected Academician of the Russian Academy of Sciences in 1907, and in 1912 he was given an honorary doctorate at Cambridge University. Following a recommendation by the Medical Academy of Paris, he was awarded the Order of the Legion of Honour in 1915.

Later Years

Later in life, Pavlov applied his laws to the study of psychosis, arguing that some people withdrew from daily interactions with others due to the association of external stimuli with a harmful event. Although he was notably dismissive of psychology as a pseudo-science, his research helped lay the groundwork of several important concepts in the then-nascent discipline.

Pavlov openly decried the war-torn conditions of his country after the Russian Revolution of 1917. He toed a dangerous line with his criticism of Communism after visits to the United States in the 1920s, though he escaped prosecution due to his standing as one of Russia's preeminent scientists. Pavlov softened his tone in the last years of his life, perhaps due to increased government support of scientific research. He remained devoted to his lab work until his death from double pneumonia on February 27, 1936, in Leningrad.

Personal Life

In 1881, Pavlov married pedagogical student Seraphima Vasilievna Karchevskaya. The couple had virtually no money in their early years together, and often lived separately until their finances stabilized. Their first son died suddenly as a young child, but they proceeded to have three more sons and a daughter.

QUICK FACTS

• Name: Ivan Petrovich Pavlov
• Birth Year: 1849
• Birth date: September 14, 1849
• Birth City: Ryazan
• Birth Country: Russia
• Gender: Male
• Best Known For: Russian physiologist Ivan Petrovich Pavlov developed his concept of the conditioned reflex through a famous study with dogs and won a Nobel Prize Award in 1904.
• Science and Medicine
• Education and Academia
• Astrological Sign: Virgo
• University of St. Petersburg
• Imperial Medical Academy
• Interesting Facts
• A dying Ivan Pavlov asked one of his students to sit by his bed to record observations of his final days.
• Death Year: 1936
• Death date: February 27, 1936
• Death City: Leningrad
• Death Country: Russia

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CITATION INFORMATION

• Article Title: Ivan Petrovich Pavlov Biography
• Author: Biography.com Editors
• Website Name: The Biography.com website
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• Last Updated: November 9, 2021
• Original Published Date: April 2, 2014
• As a young man I entered the laboratory, I have spent my entire life in it, I became an old man in it, and it is my dream to spend my final days in it.

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Classical Conditioning (Pavlov)

Classical conditioning is a reflexive or automatic type of learning in which a stimulus acquires the capacity to evoke a response that was originally evoked by another stimulus.

Contributors Key Concepts Resources and References

Contributors

• Ivan Pavlov (1849 – 1936)
• John B. Watson (1878 – 1958)

Key Concepts

Several types of learning exist. The most basic form is associative learning, i.e., making a new association between events in the environment [1] . There are two forms of associative learning: classical conditioning (made famous by Ivan Pavlov’s experiments with dogs) and operant conditioning.

Pavlov’s Dogs

In the early twentieth century, Russian physiologist Ivan Pavlov did Nobel prize-winning work on digestion [2] . While studying the role of saliva in dogs’ digestive processes, he stumbled upon a phenomenon he labeled “psychic reflexes.” While an accidental discovery, he had the foresight to see the importance of it. Pavlov’s dogs, restrained in an experimental chamber, were presented with meat powder and they had their saliva collected via a surgically implanted tube in their saliva glands. Over time, he noticed that his dogs who begin salivation before the meat powder was even presented, whether it was by the presence of the handler or merely by a clicking noise produced by the device that distributed the meat powder.

Fascinated by this finding, Pavlov paired the meat powder with various stimuli such as the ringing of a bell. After the meat powder and bell (auditory stimulus) were presented together several times, the bell was used alone. Pavlov’s dogs, as predicted, responded by salivating to the sound of the bell (without the food). The bell began as a neutral stimulus (i.e. the bell itself did not produce the dogs’ salivation). However, by pairing the bell with the stimulus that did produce the salivation response, the bell was able to acquire the ability to trigger the salivation response. Pavlov therefore demonstrated how stimulus-response bonds (which some consider as the basic building blocks of learning) are formed. He dedicated much of the rest of his career further exploring this finding.

In technical terms, the meat powder is considered an unconditioned stimulus (UCS) and the dog’s salivation is the unconditioned response (UCR). The bell is a neutral stimulus until the dog learns to associate the bell with food. Then the bell becomes a conditioned stimulus (CS) which produces the conditioned response (CR) of salivation after repeated pairings between the bell and food.

John B. Watson: Early Classical Conditioning with Humans

John B. Watson further extended Pavlov’s work and applied it to human beings [3] . In 1921, Watson studied Albert, an 11 month old infant child. The goal of the study was to condition Albert to become afraid of a white rat by pairing the white rat with a very loud, jarring noise (UCS). At first, Albert showed no sign of fear when he was presented with rats, but once the rat was repeatedly paired with the loud noise (UCS), Albert developed a fear of rats. It could be said that the loud noise (UCS) induced fear (UCR). The implications of Watson’s experiment suggested that classical conditioning could cause some phobias in humans.

Additional Resources and References

• McSweeney and Murphy: The Wiley Blackwell Handbook of Operant and Classical Conditioning. : This brand new book contains an up-to-date, inclusive account of a core field of psychology research, with in-depth coverage of operant and classical conditioning theory, its applications, and current topics including behavioral economics.
• Mackintosh, N. J. (1983). Conditioning and associative learning (p. 316). Oxford: Clarendon Press.
• Pavlov, I. P., & Anrep, G. V. (2003). Conditioned reflexes. Courier Corporation.
• Watson, J. B. (2013). Behaviorism. Read Books Ltd.

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Pavlovian Conditioning: Ivan Pavlov’s Dogs Experiment

Ivan Petrovich Pavlov (1849-1936) lived during a golden age of scientific discovery.

Born into the Russian Empire, and known within his family for being intellectually curious and unusually energetic from a young age, Pavlov won the Nobel Prize in Physiology or Medicine in 1904 for his work on the physiology of digestion, making him the first Russian Nobel laureate. Despite this, Pavlov’s most well-known contribution to science was through his dogs experiments, which became the basis for Pavlovian conditioning (also known as classical conditioning).

In this article, I’m going to look into Pavlov’s dogs experiment, followed by a detailed look at Pavlovian conditioning and Pavlovian response, before moving on to a section on further reading for anyone interested in learning more about this field.

What is Pavlov’s Dogs Experiment?

Ivan Pavlov’s dogs experiment is an experiment that took place in the 1890s in which the Russian physiologist surgically implanted small tubes into the cheeks of dogs to measure the buildup of saliva that took place under a variety of conditions.

Pavlov’s dogs experiment came about as part of an accidental discovery. Pavlov had at the time been conducting research experiments into the dogs’ gastric systems. As part of this research, Pavlov and his assistants would enter the room where the dogs were housed with a variety of edible and non-edible items, with the intention of measuring the amount of saliva that each dog produced when each item was placed in front of them.

Pavlov prediction that the dogs would salivate when presented with edible items was soon proved correct. This represents an unconditioned response in the animals, in which the sight and smell of the food causes them to salivate. Pavlov couldn’t have predicted what happened next.

A Pavlovian Response

While conducting his gastric experiment, Pavlov began to notice something peculiar. He noticed that the dogs would begin salivating not when food was placed in front of them, but when they heard the footsteps of one of Pavlov’s assistants coming down the hall to bring the food to them.

Pavlov soon realized that he could teach his dogs to associate almost any sound, item, or event with the reward of food. To put this another way, it became clear that salivation was a learned response. The most famous item used in Pavlov’s dogs experiment was that of a bell—Pavlov or one of his assistants would ring a bell before feeding his dogs. Soon enough, the single act of ringing the bell would be enough for the dogs to associate this seemingly neutral act with the promise of food.

Pavlovian conditioning was born, and Pavlov’s dogs experiment became his life’s work.

Pavlovian Conditioning

With its genesis in Pavlov’s dogs experiment, Pavlovian conditioning is defined as a form of behavioral psychology (or behaviorism) in which an animal, or human, can be conditioned to respond in a certain way to a stimulus that, had it not been conditioned, should in no way be associated with the act in question.

Let me show you what I mean:

An Unconditioned Stimulus Causes an Unconditioned Response

Prior to Pavlov’s experiment and the discovery of Pavlovian conditioning, it was well-known in the scientific world that an unconditioned stimulus causes an unconditioned response.

An example of this in terms of Pavlov’s dogs experiment would be the food being placed directly in front of the dogs, causing them to salivate. The unconditioned stimulus in this example is the food, and the unconditioned response is the salivation. Pavlov’s dogs’ response (to salivate) was unconditioned because they didn’t need to be trained to respond to the food in this way—it simply happened naturally.

A Neutral Stimulus Causes No Response

In the same way that an unconditioned stimulus causes an unconditioned response, Pavlov confirmed the commonly agreed-upon theory that a neutral stimulus causes no response.

An example of this in terms of Pavlov’s dogs experiment would be the act of Pavlov or one of his assistants ringing a bell before feeding the dogs, before they had taken the time to condition the bell as a stimulus to the food. If they were to ring the bell while it was still a neutral stimulus, no response, conditioned or unconditioned, would have occurred. (Depending on how loud the bell was, the dogs may have been startled the first few times it rang, but this is superfluous to the experiment.)

A Conditioned Stimulus Causes a Conditioned Response

Finally, Pavlov discovered through the course of his experiment that a conditioned stimulus causes a conditioned response.

An example of this in terms of Pavlov’s dogs experiment would be the act of Pavlov or one of his assistants ringing a bell before feeding the dogs, after they have already conditioned the sound of the bell to the promise of food. In this case, the sound of the bell has graduated from being a neutral stimulus to a conditioned stimulus, therefore the dogs’ response (to salivate) became a conditioned response.

Further Reading

In this article I have introduced Pavlov’s dogs experiment and Pavlovian conditioning. The field of classical conditioning and behavioral psychology is vast, and if you found this article interesting I recommend you take a look at some of the following:

• Behaviorism, Stanford Encyclopedia of Philosophy
• A Short History of Behaviorism, Washington State University
• Behavioral Principles: Classical Conditioning, St. Cloud University

Ivan Pavlov’s dogs experiment and the birth of Pavlovian conditioning was an instrumental scientific discovery at its time that deserves the acclaim and spirited conversation that it entails to this day.

If you’re interested in hearing more from me, be sure to subscribe to my free email newsletter , and if you enjoyed this article, please share it on social media, link to it from your website, or bookmark it so you can come back to it often. ∎

Benjamin Spall

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Introduction to Pavlovian Conditioning: Part 1

An object touches an infant's lips and she begins sucking. A child opens the window of a car and the blast of wind causes him to blink. The cutting of onions produces tears in the eyes of a cook. In all of these examples, a stimulus reliably produces a change in behavior. Technically the stimulus is said to elicit the response, and the relation between the stimulus and response is called a reflex. More specifically, it is an unconditioned reflex because it does not depend upon any prior learning. The stimulus is called an unconditioned stimulus (US) and the response is called an unconditioned response (UR) . For more examples of unconditioned reflexes, see Table 1 . All of these "prewired" stimulus-response connections presumably evolved because of their survival value for the individual.

Pavlovian (or Respondent or Classical) Conditioning builds on the unconditioned reflex. Pavlov (1927/1960) studied unconditioned reflexes with dogs. He found that placing meat powder in a dog's mouth (US) elicits salivation (UR). The conditioning part of his experiment involved pairing various innocuous stimuli with the food, such that they preceded food delivery. The fascinating result was that after a number of these pairings, the mere presentation of the paired stimulus elicited salivation.

For example, the sound of a bell elicits very little to no responding; for this reason it is referred to as neutral stimulus (NS) . In Pavlov's experiment, a bell was paired with food presentation. The result was that the bell came to produce a reliable change in behavior, salivation. This new relation is called a conditioned reflex . It is "conditioned" in the sense that it depends on a prior relation between the bell and the food.

A previously neutral stimulus, the bell, became an eliciting stimulus. Technically, at this point it is referred to as a conditioned stimulus (CS) and the salivation resulting from it is said to be the conditioned response(CR) . Pavlov's experiment is illustrated in Figure 1 .

The bell will remain an eliciting stimulus as long as it continues to be paired with the food. If this pairing stops, the bell will return to its neutral status and no longer reliably produce salivation. This phenomenon is known as respondent extinction .

Pavlovian Conditioning is often involved in emotions. In a frequently cited experiment ( Watson & Rayner, 1920 ), an infant boy named Albert was exposed to the sound of striking a suspended steel bar with a hammer. This sound (US) elicited fear-like responses such as crying (UR). Presentations of a white rat reliably preceded this sound; eventually the white rat itself (CS) was sufficient to elicit crying (CR). Albert was not afraid of white rats prior to the experiment; his fear of white rats, or a white rat phobia, developed during the course of the experiment due Pavlovian Conditioning.

Table 1 . Examples of Unconditioned Reflexes (adapted from Grant & Evans, 1994 p. 379)

Figure 1 . Illustration of Pavlov's conditioning experiment (adapted from Grant & Evans, 1994 ).

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Ivan Petrovich Pavlov and conditioned reflexes

Who was ivan pavlov (1849-1936).

For his original work in this field of research, Pavlov was awarded the Nobel Prize in Physiology or Medicine in 1904. By then he had turned to studying the laws on the formation of conditioned reflexes, a topic on which he worked until his death in 1936. His discoveries in this field paved the way for an objective science of behavior.

Pavlov's drooling dogs

Pavlov became interested in studying reflexes when he saw that the dogs drooled without the proper stimulus. Although no food was in sight, their saliva still dribbled. It turned out that the dogs were reacting to lab coats. Every time the dogs were served food, the person who served the food was wearing a lab coat. Therefore, the dogs reacted as if food was on its way whenever they saw a lab coat.

In a series of experiments, Pavlov then tried to figure out how these phenomena were linked. For example, he struck a bell when the dogs were fed. If the bell was sounded in close association with their meal, the dogs learnt to associate the sound of the bell with food. After a while, at the mere sound of the bell, they responded by drooling.

Different kinds of reflexes

Pavlov's discovery was that environmental events that previously had no relation to a given reflex (such as a bell sound) could, through experience, trigger a reflex (salivation). This kind of learnt response is called conditioned reflex, and the process whereby dogs or humans learn to connect a stimulus to a reflex is called conditioning.

Animals generally learn to associate stimuli that are relevant to their survival. Food aversion is an example of a natural conditioned reflex. If an animal eats something with a distinctive vanilla taste and then eats a tasteless poison that leads to nausea, the animal will not be particularly eager to eat vanilla-flavoured food the next time. Linking nausea to taste is an evolutionarily successful strategy, since animals that failed to learn their lesson did not last very long.

Why were Pavlov's findings given so much acknowledgment?

Pavlov's description on how animals (and humans) can be trained to respond in a certain way to a particular stimulus drew tremendous interest from the time he first presented his results. His work paved the way for a new, more objective method of studying behavior.

So-called Pavlovian training has been used in many fields, with anti-phobia treatment as but one example. An important principle in conditioned learning is that an established conditioned response (salivating in the case of the dogs) decreases in intensity if the conditioned stimulus (bell) is repeatedly presented without the unconditioned stimulus (food). This process is called extinction.

Conditioning forms the basis of much of learned human behavior. Nowadays, this knowledge has also been exploited by commercial advertising. An effective commercial should be able to manipulate the response to a stimulus (like seeing a product's name) which initially does not provoke any feeling. The objective is to train people to make the "false" connection between positive emotions (e.g. happiness or feeling attractive) and the particular brand of consumer goods being advertised.

Pavlov's prize

Until Pavlov started to scrutinize this field, our knowledge of how food was digested in the stomach, and what mechanisms were responsible for regulating this, were quite foggy.

In order to understand the process, Pavlov developed a new way of monitoring what was happening. He surgically made fistulas in animals' stomachs, which enabled him to study the organs and take samples of body fluids from them while they continued to function normally.

By Lotta Fredholm, Science Journalist

More about Nobel Laureate Ivan Pavlov

Play the Pavlov's Dog Game

First published 15 May 2001

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Biography of Ivan Pavlov, Father of Classical Conditioning

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Ivan Petrovich Pavlov (September 14, 1849 - February 27, 1936) was a Nobel Prize-winning physiologist best known for his classical conditioning experiments with dogs. In his research, he discovered the conditioned reflex, which shaped the field of behaviorism in psychology.

Fast Facts: Ivan Pavlov

• Occupation : Physiologist
• Known For : Research on conditioned reflexes ("Pavlov's Dogs")
• Born : September 14, 1849, in Ryazan, Russia
• Died : February 27, 1936, in Leningrad (now St. Petersburg), Russia
• Parents : Peter Dmitrievich Pavlov and Varvara Ivanovna Uspenskaya
• Education : M.D., Imperial Medical Academy in St. Petersburg, Russia
• Key Accomplishments : Nobel Prize for Physiology (1904)
• Offbeat Fact : A lunar crater on the Moon was named after Pavlov.

Early Years and Education

Pavlov was born on September 14, 1849, in the small village of Ryazan, Russia. His father, Peter Dmitrievich Pavlov, was a priest who hoped that his son would follow in his footsteps and join the church. In Ivan's early years, it seemed that his father's dream would become a reality. Ivan was educated at a church school and a theological seminary. But when he read the works of scientists like Charles Darwin and I. M. Sechenov, Ivan decided to pursue scientific studies instead.

He left the seminary and began studying chemistry and physiology at the University of St. Petersburg. In 1875, he earned an M.D. from the Imperial Medical Academy before going on to study under Rudolf Heidenhain and Carl Ludwig, two renowned physiologists. 

Personal Life and Marriage

Ivan Pavlov married Seraphima Vasilievna Karchevskaya in 1881. Together, they had five children: Wirchik, Vladimir, Victor, Vsevolod, and Vera. In their early years, Pavlov and his wife lived in poverty. During the hard times, they stayed with friends, and at one point, rented a bug-infested attic space.

Pavlov's fortunes changed in 1890 when he took an appointment as the Professor of Pharmacology at the Military Medical Academy. That same year, he became the director of the Department of Physiology at the Institute of Experimental Medicine. With these well-funded academic positions, Pavlov had the opportunity to further pursue the  scientific studies  that interested him.

Research on Digestion

Pavlov's early research focused primarily on the physiology of digestion . He used surgical methods to study various processes of the digestive system. By exposing portions of a dog's intestinal canal during surgery, he was able to gain an understanding of gastric secretions and the role of the body and mind in the digestive process. Pavlov sometimes operated on live animals, which was an acceptable practice back then but would not occur today due to modern ethical standards.

In 1897, Pavlov published his findings in a book called “Lectures on the Work of the Digestive Glands.” His work on the physiology of digestion was also recognized with a Nobel Prize for Physiology in 1904. Some of Pavlov's other honors include an honorary doctorate from Cambridge University, which was awarded in 1912, and the Order of the Legion of Honor, which was given to him in 1915.

Discovery of Conditioned Reflexes

Although Pavlov has many notable accomplishments, he is most well known for defining the concept of conditioned reflexes. 

A conditioned reflex is considered a form of learning that can occur through exposure to stimuli. Pavlov studied this phenomenon in the lab through a series of experiments with dogs. Initially, Pavlov was studying the connection between salivation and feeding. He proved that dogs have an unconditioned response when they are fed — in other words, they are hard-wired to salivate at the prospect of eating.

However, when Pavlov noticed that the mere sight of a person in a lab coat was enough to cause the dogs to salivate, he realized that he had accidentally made an additional scientific discovery. The dogs had learned that a lab coat meant food, and in response, they salivated every time they saw a lab assistant. In other words, the dogs had been conditioned to respond a certain way. From this point on, Pavlov decided to devote himself to the study of conditioning.

Pavlov tested his theories in the lab using a variety of neural stimuli. For example, he used electric shocks, a buzzer that produced specific tones and the ticking of a metronome to make the dogs associate certain noises and stimuli with food. He found that not only could he cause a conditioned response (salivation), he could also break the association if he made these same noises but did not give the dogs food.

Even though he was not a psychologist, Pavlov suspected that his findings could be applied to humans as well. He believed that a conditioned response may be causing certain behaviors in people with psychological problems and that these responses could be unlearned. Other scientists, such as John B. Watson, proved this theory correct when they were able to replicate Pavlov's research with humans. 

Pavlov worked in the lab until his death at the age of 86. He died on February 27, 1936, in Leningrad (now St. Petersburg), Russia after contracting double pneumonia. His death was commemorated with a grand funeral and a monument that was erected in his home country in his honor. His laboratory was also turned into a museum.

Legacy and Impact

Pavlov was a physiologist, but his legacy is primarily recognized in psychology and educational theory. By proving the existence of conditioned and non-conditioned reflexes, Pavlov provided a foundation for the study of behaviorism. Many renowned psychologists, including John B. Watson and  B. F. Skinner , were inspired by his work and built on it to gain a better understanding of behavior and learning.

To this day, nearly every student of psychology studies Pavlov's experiments to gain a better understanding of the scientific method , experimental psychology, conditioning, and behavioral theory. Pavlov's legacy can also be seen in popular culture in books like Aldous Huxley's " Brave New World ", which contained elements of Pavlovian conditioning.

• Cavendish, Richard. “Death of Ivan Pavlov.” History Today .
• Gantt, W. Horsley. “ Ivan Petrovich Pavlov. ” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 20 Feb. 2018.
• McLeod, Saul. “Pavlov's Dogs.” Simply Psychology, 2013 .
• Tallis, Raymond. “The Life of Ivan Pavlov.” The Wall Street Journal, 14 Nov. 2014 .
• “Ivan Pavlov - Biographical.” Nobelprize.org .
• “Ivan Pavlov.” PBS, Public Broadcasting Service .
• What Is a Conditioned Response?
• What Is an Unconditioned Response?
• What Is Classical Conditioning?
• What Is Behaviorism in Psychology?
• What Is Operant Conditioning? Definition and Examples
• What Is the Law of Effect in Psychology?
• Implicit Bias: What It Means and How It Affects Behavior
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• Cultivation Theory

Famous Scientists

Ivan Pavlov

Ivan Petrovich Pavlov was an eminent Russian physiologist and psychologist who devised the concept of the conditioned reflex. He conducted a legendary experiment in which he trained a hungry dog to drool at the sound of a bell, which had previously been related to the presentation of food to the animal.

Pavlov formulated a conceptual theory, highlighting the significance of conditioning and associating human behavior with the nervous system. He was awarded the 1904 Nobel Prize for Physiology or Medicine for his groundbreaking research on digestive secretions.

Early Life and Education:

Ivan Pavlov was born in Ryazan, Russia on the 26 September 1849, the eldest of eleven children. His father, Peter Dmitrievich Pavlov, was a Russian orthodox priest and his mother was Varvara Ivanovna Uspenskaya. As a young child, he suffered a serious injury from a fall, due to which Pavlov spent much of his early childhood with his parents in the family home and garden. There he acquired various practical skills and a deep interest in natural history.

Enrolling at a church school aged eleven; Pavlov continued his education at the university of St. Petersburg where he studied physics, mathematics and natural sciences.

Pavlov developed a strong interest in science and considered the possibility of using science to ameliorate and modify society.

Career Path:

After graduating from St. Petersburg in 1875, he studied medicine at the Imperial Academy of Medical Surgery under the famed physiologist of the time, Sergey Petrovich Botkin, who taught him a great deal about the nervous system. Pavlov received his medical degree in 1879, earning a gold medal award for his research work.

Pavlov remained in St. Petersburg, conducting postgraduate research and he obtained the position of director of the Physiological Laboratory at Botkin’s clinic.

He married Seraphima Vasilievna Karchevskaya, a teacher, in 1881 and they had five children.

In 1883, he earned his doctorate with his thesis, “The centrifugal nerves of the heart”.

After completing his doctorate, Pavlov spent two years in Germany studying digestion in dogs.

In 1886 he returned to Russia but could not find a position until 1890 when he was appointed to the role of professor of Pharmacology at the Military Medical Academy. In 1895 he was appointed to the chair of physiology and remained at the Academy until he resigned in 1924.

Pavlov also organized carried out research at the newly founded Institute of Experimental Medicine, which under his direction spanning over four decades, became one of the most important world centers of physiological research.

Contributions and Achievements:

Ivan Pavlov conducted neurophysiological experiments with animals for years after receiving his doctorate at the Academy of Medical Surgery. He became fully convinced that human behavior could be understood and explained best in physiological terms rather than in mentalist terms. The legendary experiment for which Pavlov is remembered was when he used the feeding of dogs to establish a number of his key ideas.

Moments before feeding, a bell was rung to measure the dogs’ saliva production when they heard the bell. Pavlov discovered that once the dogs had been trained to associate the sound of the bell with food, they would produce saliva, whether or not food followed. The experiment proved that the dogs’ physical response, salivation, was directly related to the stimulus of the bell, hence the saliva production was a stimulus response. The continued increased salivation, even when the dogs had experienced hearing the bell without being later fed, was a conditioned reflex.

The entire process is a prime example of classical conditioning, and it is primarily related to a physical and spontaneous response to some particular conditions that the organism has acquired through association. Behaviorist theory has applied these landmark ideas for the explanation of human behavior.

In 1904 he was awarded a Nobel Prize for “in recognition of his work on the physiology of digestion, through which knowledge on vital aspects of the subject has been transformed and enlarged.”

He was elected Academician of the Russian Academy of Sciences in 1907 and in 1915 he received the Order of the Legion of Honor.

Later Life and Death:

Ivan Pavlov died on February 27, 1936 in Leningrad, Soviet Union, from natural causes. He was 86 years old.

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As a college student, B. F. Skinner gave little thought to psychology. He had hoped to become a novelist, and majored in English. Then, in 1927, when he was twenty-three, he read an essay by H. G. Wells about the Russian physiologist Ivan Pavlov. The piece, which appeared in the Times Magazine , was ostensibly a review of the English translation of Pavlov’s “Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex.” But, as Wells pointed out, it was “not an easy book to read,” and he didn’t spend much time on it. Instead, Wells described Pavlov, whose systematic approach to physiology had revolutionized the study of medicine, as “a star which lights the world, shining down a vista hitherto unexplored.”

That unexplored world was the mechanics of the human brain. Pavlov had noticed, in his research on the digestive system of dogs, that they drooled as soon as they saw the white lab coats of the people who fed them. They didn’t need to see, let alone taste, the food in order to react physically. Dogs naturally drooled when fed: that was, in Pavlov’s terms, an “unconditional” reflex. When they drooled in response to a sight or sound that was associated with food by mere happenstance, a “conditional reflex” (to a “conditional stimulus”) had been created. Pavlov had formulated a basic psychological principle—one that also applied to human beings—and discovered an objective way to measure how it worked.

Skinner was enthralled. Two years after reading the Times Magazine piece, he attended a lecture that Pavlov delivered at Harvard and obtained a signed picture, which adorned his office wall for the rest of his life. Skinner and other behaviorists often spoke of their debt to Pavlov, particularly to his view that free will was an illusion, and that the study of human behavior could be reduced to the analysis of observable, quantifiable events and actions.

But Pavlov never held such views, according to “Ivan Pavlov: A Russian Life in Science” (Oxford), an exhaustive new biography by Daniel P. Todes, a professor of the history of medicine at Johns Hopkins School of Medicine. In fact, much of what we thought we knew about Pavlov has been based on bad translations and basic misconceptions. That begins with the popular image of a dog slavering at the ringing of a bell. Pavlov “never trained a dog to salivate to the sound of a bell,” Todes writes. “Indeed, the iconic bell would have proven totally useless to his real goal, which required precise control over the quality and duration of stimuli (he most frequently employed a metronome, a harmonium, a buzzer, and electric shock).”

Pavlov is perhaps best known for introducing the idea of the conditioned reflex, although Todes notes that he never used that term. It was a bad translation of the Russian uslovnyi , or “conditional,” reflex. For Pavlov, the emphasis fell on the contingent, provisional nature of the association—which enlisted other reflexes he believed to be natural and unvarying. Drawing upon the brain science of the day, Pavlov understood conditional reflexes to involve a connection between a point in the brain’s subcortex, which supported instincts, and a point in its cortex, where associations were built. Such conjectures about brain circuitry were anathema to the behaviorists, who were inclined to view the mind as a black box. Nothing mattered, in their view, that could not be observed and measured. Pavlov never subscribed to that theory, or shared their disregard for subjective experience. He considered human psychology to be “one of the last secrets of life,” and hoped that rigorous scientific inquiry could illuminate “the mechanism and vital meaning of that which most occupied Man—our consciousness and its torments.” Of course, the inquiry had to start somewhere. Pavlov believed that it started with data, and he found that data in the saliva of dogs.

Pavlov’s research originally had little to do with psychology; it focussed on the ways in which eating excited salivary, gastric, and pancreatic secretions. To do that, he developed a system of “sham” feeding. Pavlov would remove a dog’s esophagus and create an opening, a fistula, in the animal’s throat, so that, no matter how much the dog ate, the food would fall out and never make it to the stomach. By creating additional fistulas along the digestive system and collecting the various secretions, he could measure their quantity and chemical properties in great detail. That research won him the 1904 Nobel Prize in Physiology or Medicine. But a dog’s drool turned out to be even more meaningful than he had first imagined: it pointed to a new way to study the mind, learning, and human behavior.

“Essentially, only one thing in life is of real interest to us—our psychical experience,” he said in his Nobel address. “Its mechanism, however, was and still is shrouded in profound obscurity. All human resources—art, religion, literature, philosophy, and the historical sciences—all have joined in the attempt to throw light upon this darkness. But humanity has at its disposal yet another powerful resource—natural science with its strict objective methods.”

Pavlov had become a spokesman for the scientific method, but he was not averse to generalizing from his results. “That which I see in dogs,” he told a journalist, “I immediately transfer to myself, since, you know, the basics are identical.”

Ivan Pavlov was born in 1849 in the provincial Russian city of Ryazan, the first of ten children. As the son of a priest, he attended church schools and the theological seminary. But he struggled with religion from an early age and, in 1869, left the seminary to study physiology and chemistry at St. Petersburg University. His father was furious, but Pavlov was undeterred. He never felt comfortable with his parents—or, as this biography makes clear, with almost anyone else. Not long after “The Brothers Karamazov” was published, Pavlov confessed to his future wife, Seraphima Vasilievna Karchevskaya, who was a friend of Dostoyevsky’s, that he identified with the rationalist Ivan Karamazov, whose brutal skepticism condemned him, as Todes notes, to nihilism and breakdown. “The more I read, the more uneasy my heart became,” Pavlov wrote in a letter to Karchevskaya. “Say what you will, but he bears a great resemblance to your tender and loving admirer.”

Pavlov entered the intellectual world of St. Petersburg at an ideal moment for a man eager to explore the rules that govern the material world. The tsar had freed the serfs in 1861, helping to push Russia into the convulsive century that followed. Darwin’s theory of evolution was starting to reverberate across Europe. Science began to matter in Russia in a way it hadn’t before. At the university, Pavlov’s freshman class in inorganic chemistry was taught by Dmitri Mendeleev, who, a year earlier, had created the periodic table of the elements as a teaching tool. The Soviets would soon assign religion to the dustbin of history, but Pavlov got there ahead of them. For him, there was no religion except the truth. “It is for me a kind of God, before whom I reveal everything, before whom I discard wretched worldly vanity,” he wrote. “I always think to base my virtue, my pride, upon the attempt, the wish for truth , even if I cannot attain it.” One day, while walking to his lab at the Institute for Experimental Medicine, Pavlov watched with amazement as a medical student stopped in front of a church and crossed himself. “Think about it!” Pavlov told his colleagues. “A naturalist, a physician, but he prays like an old woman in an almshouse!”

Pavlov was not a pleasant person. Todes presents him as a volatile child, a difficult student, and, frequently, a nasty adult. For decades, his lab staff knew to stay away, if at all possible, on his “angry days,” and there were many. As a member of the liberal intelligentsia, he was opposed to restrictive measures aimed at Jews, but in his personal life he freely voiced anti-Semitic sentiments. Pavlov once referred to “that vile yid, Trotsky,” and, when complaining about the Bolsheviks in 1928, he told W. Horsley Gantt, an American scientist who spent years in his lab, that Jews occupied “high positions everywhere,” and that it was “a shame that the Russians cannot be rulers of their own land.”

In lectures, Pavlov insisted that medicine had to be grounded in science, on data that could be explained, verified, and analyzed, and on studies that could be repeated. Drumming up support among physicians for the scientific method may seem banal today, but at the end of the nineteenth century it wasn’t an easy sell. In Russia, and even to some degree in the West, physiology was still considered a “theoretical science,” and the connection between basic research and medical treatments seemed tenuous. Todes argues that Pavlov’s devotion to repeated experimentation was bolstered by the model of the factory, which had special significance in a belatedly industrializing Russia. Pavlov’s lab was essentially a physiology factory, and the dogs were his machines.

To study them, he introduced a rigorous experimental approach that helped transform medical research. He recognized that meaningful changes in physiology could be assessed only over time. Rather than experiment on an animal once and then kill it, as was common, Pavlov needed to keep his dogs alive. He referred to these studies as “chronic experiments.” They typically involved surgery. “During chronic experiments, when the animal, having recovered from its operation, is under lengthy observation, the dog is irreplaceable,” he noted in 1893.

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The dogs may have been irreplaceable, but their treatment would undoubtedly cause an outcry today. Todes writes that in early experiments Pavlov was constantly stymied by the difficulty of keeping his subjects alive after operating on them. One particularly productive dog had evidently set a record by producing active pancreatic juice for ten days before dying. The loss was a tremendous disappointment to Pavlov. “Our passionate desire to extend experimental trials on such a rare animal was foiled by its death as a result of extended starvation and a series of wounds,” Pavlov wrote at the time. As a result, “the expected resolution of many important and controversial questions” had been delayed, awaiting another champion test subject.

If Pavlov’s notes were voluminous, Todes’s own investigations are hardly modest. He spent years researching this biography and has made excellent use of archives in Russia, Europe, and the United States. No scholar of Pavlov or of the disciplines he inspired will be able to ignore this achievement. The book’s eight hundred and fifty-five pages are filled with a vast accumulation of data, although the reader might have been better served if Todes had left some of it out. No minutia appears to have been too obscure to include. Here is Todes describing data that Pavlov had assembled from one extended experiment: “The total amount of secretion in trials 6 and 8 is too low, and the slope of these curves diverges markedly at several points from that in trial 1. Trial 9 fits trial 1 more snugly than does trial 5 in terms of total secretion, but the amount of secretion more than doubles in the second hour, contrasting sharply with the slight decline in trial 1. Trial 10 is again a good fit in terms of total amount of secretion, but the amount of secretion rises inappropriately in the fourth hour.” The diligent reader can also learn, in excruciating detail, what time Pavlov took each meal during summer holidays (dinner at precisely 12:30 P . M ., tea at four, and supper at eight), how many cups of tea he typically consumed each afternoon (between six and ten), and where the roses were planted in his garden (“around the spruce tree on the west side of the veranda”). It’s hard not to wish that Todes had been a bit less devoted to his subject’s prodigious empiricism.

For more than thirty years, Pavlov’s physiology factory turned out papers, new research techniques, and, of course, gastric juice—a lot of it. On a good day, a hungry dog could produce a thousand cubic centimetres, more than a quart. Although this was a sideline for Pavlov, the gastric fluids of a dog became a popular treatment for dyspepsia, and not just in Russia. A “gastric juice factory” was set up for the purpose. “An assistant was hired and paid thirty rubles a month to oversee the facility,” Todes writes. “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 venture was selling more than three thousand flagons of gastric juice annually, Todes writes, and the profits helped increase the lab budget by about seventy per cent. The money was helpful. So was the apparent demonstration that a product created in an experimental laboratory could become useful to doctors all over the world.

At the turn of the century, Pavlov had begun focussing his research on “psychic secretions”: drool produced by anything other than direct exposure to food. He spent most of the next three decades exploring the ways conditional reflexes could be created, refined, and extinguished. Before feeding a dog, Pavlov might set a metronome at, say, sixty beats a minute. The next time the dog heard a metronome at any speed, it would salivate. But when only that particular metronome setting was reinforced with food the dog became more discriminating. Pavlov deduced that there were colliding forces of “excitation” and “inhibition” at play—so that, at first, the stimulus spreads across the cerebral cortex and then, in the second phase, it concentrates at one specific spot.

As his formulations and models grew more complex, Pavlov was encouraged in his hope that he would be able to approach psychology through physiology. “It would be stupid to reject the subjective world,” he remarked later. “Our actions, all forms of social and personal life are formed on this basis. . . . The question is how to analyze this subjective world.”

Pavlov was sixty-eight and had been famous for years when Lenin came to power, and Todes is at his best in describing the scientist’s relationship with the regime that he would serve for the rest of his life. Pavlov harbored no sentimental attachment to the old order, which had never been aggressive in funding scientific research. The Bolsheviks promised to do better (and, eventually, they did). Yet Pavlov considered Communism a “doomed” experiment that had turned Russia back into a nation of serfs. “Of course, in the struggle between labor and capital the government must stand for the protection of the worker,” he said in a speech. “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.”

Lenin had too many other problems to spend his time worrying about one angry scientist. At first, Pavlov, his wife, and their four children were treated like any other Soviet citizens. Their Nobel Prize money was confiscated as property of the state. From 1917 to 1920, like most residents of Petrograd, which would soon be called Leningrad, the Pavlovs struggled to feed themselves and to keep from freezing. It was nearly a full-time occupation; at least a third of Pavlov’s colleagues at the Russian Academy of Sciences died in those first post-revolutionary years. “Some starved to death in apartments just above or below his own in the Academy’s residence,” Todes writes. Pavlov grew potatoes and other vegetables right outside his lab, and when he was sick a colleague provided small amounts of firewood to burn at home.

In 1920, Pavlov wrote to Lenin’s secretary, Vladimir Bonch-Bruevich, seeking permission to emigrate, although, as Todes points out, it was probably not yet necessary to ask. Pavlov wanted to see if, as he suspected, universities in Europe or America would fund his research in circumstances that would prevent his dogs and lab workers from starving. Bonch-Bruevich turned the letter over to Lenin, who immediately grasped the public-relations repercussions of losing the country’s most celebrated scientist. He instructed Petrograd Party leaders to increase rations for Pavlov and his family, and to make sure his working conditions improved.

The Soviets came to regard Pavlov as a scientific version of Marx. The comparison could not entirely have pleased Pavlov, who rebelled at the “divine” authority accorded Marx (“that fool”) and denied that his own “approach represents pure materialism.” Indeed, where others thought that the notion of free will would come to be discarded once we had a full understanding of how the mind worked, Pavlov was, at least at times, inclined to think the opposite. “We would have freedom of the will in proportion to our knowledge of the brain,” he told Gantt in 1927, just as “we had passed from a position of slave to a lord of nature.”

That year, Stalin began a purge of intellectuals. Pavlov was outraged. At a time when looking at the wrong person in the wrong way was enough to send a man to the gulag, he wrote to Stalin saying that he was “ashamed to be called a Russian.” Nikolai Bukharin, who considered Pavlov indispensable, made the case for him: “I know that he does not sing the ‘Internationale,’ ” Bukharin wrote to Valerian Kuibyshev, the head of the state planning committee. “But . . . despite all his grumbling, ideologically (in his works, not in his speeches) he is working for us.”

Stalin agreed. Pavlov prospered even at the height of the Terror. By 1935-36, he was running three separate laboratories and overseeing the work of hundreds of scientists and technicians. He was permitted to collaborate with scholars in Europe and America. Still, his relationship with the government was never easy. Soviet leaders even engaged in a debate over whether to celebrate his eightieth birthday. “A new nonsensical letter from academician Pavlov,” Molotov wrote in the margin of a letter of complaint before it was passed to Stalin. Kuibyshev was deeply opposed to any state recognition. “Pavlov spits on the Soviets, declares himself an open enemy, yet Soviet power would for some reason honor him,” he grumbled. “Help him we must,” he said at the time, “but not honor him.” For a while, Kuibyshev prevailed, but in 1936, when Pavlov died, at eighty-six, a hundred thousand mourners, including Party officials, filed past his casket as he lay in state.

What Todes describes as Pavlov’s “grand quest”—to rely on saliva drops and carefully calibrated experiments to understand the mechanics of human psychology—lives on, in various forms. Classical conditioning remains a critical tool: it is widely used to treat psychiatric disorders, particularly phobias. But the greater pursuit is for a kind of unified field theory in which psychology and physiology—the subjective and the material realms—would finally be integrated.

And so we have entered the age of the brain. The United States and other countries have embarked upon brain-mapping initiatives, and Pavlov would have endorsed their principal goal: to create a dynamic picture of the brain that demonstrates, at the cellular level, how neural circuits interact. As Todes points out, while Pavlov examined saliva in his attempts to understand human psychology, today we use fMRIs in our heightened search for the function of every neuron. When he delivered his lectures on the “larger hemispheres of the brain,” Pavlov declared, “We will hope and patiently await the time when a precise and complete knowledge of our highest organ, the brain, will become our profound achievement and the main foundation of a durable human happiness.” We are still waiting, but less patiently than before. ♦

Behaviorism

An aged tortoise tells us much about pavlovian conditioning, pavlov's broad theory of behavioral adaptation was never just about salivation..

Posted August 29, 2024 | Reviewed by Michelle Quirk

• Most think that Pavlovian conditioning is a rudimentary form of learning limited to reflexes like salivation.
• Pavlov's own theory of signalization was far more encompassing.
• Signalization applied not only to reflexive consummatory responses, but to preparatory locomotor responses.

As he nears 200 years of age, Jonathan the tortoise has been receiving a great deal of international attention . However, longevity is not the only reason why we should find Jonathan to be of special interest. He’s confirming what Pavlov said about conditioning a century ago: It isn’t just about salivation!

Jonathan is a giant tortoise ( Aldabrachelys gigantea hololissa ) who, in 1882, was shipped from his original home in the Seychelles Islands in the Indian Ocean to Saint Helena—a volcanic tropical island and British Overseas Territory located in the South Atlantic Ocean some 1,200 miles off the west coast of Africa. Jonathan is estimated to be 192 years old, having “officially” hatched on December 4, 1832, making him the oldest living land animal according to the Guinness Book of World Records (Atwal, 2022). Jonathan turns out to be Saint Helena’s second most famous expatriate inhabitant, its first being Napoleon Bonaparte, who was exiled there in 1815 in the wake of his ignominious defeat at the Battle of Waterloo.

Jonathan is still in fine fettle despite his advanced age, thanks in great measure to the assiduous care he’s received for the past 15 years from veterinarian Joe Hollins. Although the nearly 400-pound chelonian has lost his senses of smell and sight, his hearing is quite acute. That enduring sense is crucial to the vital lesson Jonathan teaches us about Pavlovian conditioning.

Hollins has made a number of astute observations of Jonathan’s feeding activity: “He knows my voice and comes to me like a dog, but I have to accept it is mainly Pavlovian because he associates me with food” (Free, 2022). Further elaborating, Hollins stresses the fervor of Jonathan’s Pavlovian reactions: “He recognizes my voice when I approach and call to him softly. He literally jerks to attention and starts biting the air” (Free, 2024).

There’s no mystery as to how such Pavlovian conditioning has taken place. For many years, Hollins’ voice has consistently preceded Jonathan’s weekly repast of fresh fruit and vegetables—variously including bananas, apples, pears, carrots, cucumbers, cabbage, and hearts of lettuce—which supplement the giant tortoise’s far less delectable fare of grass and clover.

Now, by way of comparison, consider Pavlov’s (1934) characterization of the conditioned motor responses exhibited by his dogs:

"The first reaction elicited by the established conditioned stimulus usually consists in a movement towards the stimulus, i.e., the animal turns to the place where the stimulus is to be found. If the stimulus is within reach, the animal even tries to come in touch with it, namely, by means of its mouth. Thus, if the conditioned stimulus is the switching on of a lamp, the dog licks the lamp; if the conditioned stimulus is a sound the dog will even snap at the air (in case of very heightened food excitability)."

The resemblance between Pavlov’s description of his dogs’ conditioned responding and Hollins’s description of Jonathan’s conditioned responding is striking. What is also striking is that the specific behaviors being highlighted—orienting, approaching, and biting—are overtly directed toward the conditioned stimulus, whether it be visual or auditory.

So, what’s happened to that most exemplary of Pavlovian conditioned responses—salivation?

Nothing at all. Both dogs and tortoises avidly salivate and manipulate food in their mouths. Pavlov’s strong focus on salivation as the target response in much of his other scientific writings was the natural extension of his prior research in digestion, for which he was awarded the Nobel Prize in Physiology or Medicine in 1904. In addition, while conducting that work, Pavlov diligently devised highly accurate methods to measure secretory activity; similarly accurate measures were not then available to investigate motor activity. Finally, Pavlov dedicated himself to providing an entirely objective explanation of his pioneering findings. He firmly believed that focusing on dogs’ salivation would be more conducive to achieving this goal than would focusing on dogs’ directed motor responses for the simple reason that, in the case of secretory responses, there would probably be a “much smaller tendency to interpret them in an anthropomorphic fashion” (1927).

By integrating his meticulous measurements of salivary secretion with his more informal observations of directed motor activity, Pavlov was able to propose a comprehensive theory of associative conditioning. Here’s how Pavlov explained this theory: Although animals may be equipped by evolution with a host of generally adaptive inborn responses, many of those responses may not be suited to the specific environmental conditions that animals encounter in their everyday lives. Those particular conditions may demand more fine-tuning, which becomes the business of the brain—the bodily organ that can effectively and flexibly link adaptive behaviors with environmental stimuli. To this key function of the brain, Pavlov gave the name signalization , and to these experientially acquired signals, he gave the name conditioned stimuli (1927).

Pavlov’s laboratory experiments famously showed that “artificial” conditioned stimuli (such as a ticking metronome) that are arbitrarily paired with food, as well as “natural” conditioned stimuli (such as the smell and sight of food) that are ordinarily paired with food in the development of a dog’s normal feeding behavior, could each serve as highly effective signals. Indeed, in the latter case, Pavlov surprisingly documented that puppies do not unconditionally salivate to the smell or sight of foods like meat and bread; only after the puppies had previously eaten those foods did their smell or sight come to trigger salivation.

Pavlov had one more critical point to make about signalization. Yes, it is highly adaptive for the proximal presentation of food in the mouth to unconditionally stimulate copious quantities of saliva, and in so doing to promote swallowing and digestion. Of even greater importance, however, is for the distal presentation of a signaling stimulus to conditionally elicit the motor components of nutrition , thus instigating the pursuit of food (1927). After all, you can’t eat the food if you don’t first detect its presence, approach it, and then seize it. Hence comes Pavlov’s bold exclamation: “How many simple physiological reflexes start from the nose, the eye, and the ear, and therefore originate at a distance!” (1928).

In Pavlov’s theory of signalization, the movement reactions of animals are put front and center in a fully integrative analysis of adaptive behavior: “By means of distant and even accidental characteristics of objects the animal seeks his food, avoids his enemies, etc.” (1928).

As noted earlier, Jonathan has lost his senses of smell and sight. Yet, his still-functioning sense of hearing enables Jonathan to locate Hollins, to approach him, and, in a state of heightened food excitability, to bite at the air—just like Pavlov’s dogs.

Hatched some 17 years before Pavlov’s birth and living some 88 years after Pavlov’s death, Jonathan provides persuasive support for Pavlov’s theory of conditioned responding. Adaptive behaviors—both secretory and motor—can be refined by experiences that are unique to an individual animal through the participation of the distance receptors and the brain. Signalization thus represents the theoretical complement to Pavlov’s pioneering empirical investigations—a theory that makes it clear that Pavlovian conditioning was never just about salivation.

A version of this post also appears in the APS Observer.

Atwal, S. (2022, January 12). 190-year-old Jonathan becomes world’s oldest tortoise ever. Guinness World Records.

Free, C. (2022, January 30). The world’s oldest living land animal? At age 190, it’s Jonathan the tortoise. Washington Post .

Free, C. (2024, January 1). Happy 191st (or so) birthday to the world’s oldest living land animal. Washington Post .

Pavlov, I. P. (1927). Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex. Translated and edited by G. V. Anrep. Oxford University Press.

Pavlov, I. P. (1928). Lectures on Conditioned Reflexes: Twenty-Five Years of Objective Study of the Higher Nervous Activity (Behaviour) of Animals. (W. H. Gantt, Trans.). Liverwright Publishing Corporation. https://doi.org/10.1037/11081-000

Pavlov, I. P. (1934). An attempt at a physiological interpretation of obsessional neurosis and paranoia. Journal of Mental Science , 80 , 187–197. https://doi.org/10.1192/bjp.80.329.187-a

Ed Wasserman, Ph.D., studies learning, memory, and cognition at The University of Iowa.

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