Pavlov’s Dog Experiments

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Ivan Pavlov, a Russian physiologist, is renowned for his groundbreaking research on classical conditioning. Pavlov’s dog experiments have become one of the most iconic studies in the field of psychology. Pavlov’s dog experiments involved a simple yet ingenious setup to measure the saliva of dogs in response to a stimulus (food).

Pavlov observed that dogs naturally salivated when presented with food, an automatic response known in classical conditioning as the unconditioned response (UR). Pavlov utilized this natural reflex as a baseline for his research. In Pavlov’s dog experiments, Pavlov theorized that dogs could be conditioned to associate a neutral stimulus (such as a bell) with a reflexive response (such as salivation) by repeatedly pairing the two stimuli together.

Key Definition:

Pavlov’s dogs experiments refer to a series of experiments conducted by Ivan Pavlov in the late 19th century. He discovered he could condition a dog to salivate at the sound of a bell. Pavlov’s research is a prominent element in the upcoming behaviorist movement occurring during that at time.

History of the Classical Conditioning of the Pavlov Dogs.

Ivan Pavlov was born on September 14, 1849 in the small Russian town of Ryazan. One of Palov’s primary subjects of research was the physiology of digestion. He observed and meticulous recorded the digestive process in dogs. As far back as 1890, he noted that an interesting phenomenon occurred around feeding and sham feeding time with the gastric secretion. He was especially interested in the secretion of gastric juices at the mere sight of food. This psychic component of a physiological occurrence became the subject of his later investigations, providing substantial empirical support for the behaviorist movement and the concept of classical (Pavlovian) conditioning.

His observations later motivated the transition from the physiology of digestion to the psychology of reflexes. One of the chief impetuses for this transition, in addition to his observations, was a booklet he read in his youth from Mikhailovich Sechenov, the father of Russian physiology, entitled Reflexes of the Brain.

The Involvement of the Psychic Component in Physiological Processes

“It became increasingly obvious to Pavlov that a ‘psychic’ component was of unexpected large significance in the content of digestive secretions” (Kimble, 1967, p. 29). The basic concept in Pavlovian conditioning is that “the ultimate nature of conditioning was that intense (dominant) activity (excitation) set up in one neural center by the unconditioned stimulus (US) attracted to itself the weaker activity (excitation) initiated by other stimuli present at approximately the same time” (p.35). Basically, when food excites the salivatory glands at the same time as an unconditioned stimulus is present (such as a bell or flash of light), the two elements merge, creating a temporary connection.

“Neurons that fire together, wire together.”
~Donald Hebb (1949)

The ultimate outcome of this temporary wiring is that now the US (the bell or the flashing light) excites the primary reflex. In the Pavlov experiments this refers to the reflexive excretion of saliva. After conditioning, the bell would begin the flow of digestive juices without the presence of food.

The Experiments

The experiments required measuring the flow of saliva. To do this, Pavlov and his lab assistances performed a simple operation, making “a permanent fistula of the parotid duct—that is, a small opening is made to lead from the gland to the external surface of the cheek and a small tube is cemented to this outlet” (Watson, 2012, pp. 26-27). Researchers were than able to measure and record the drops of saliva coming from the gland.

To test the concept of classical conditioning, Pavlov introduced a neutral stimulus, typically the sound of a bell, before presenting the dogs with food. Initially, the bell had no inherent association with salivation. However, after repeatedly pairing the bell with the food, the dogs began to associate the bell with the forthcoming meal. After a “psychic” connection was formed between the bell and the forth coming meal, the bell would excite the digestive gland and drops of saliva would flow from the parotid duct.

Palov explains that by connecting the unconditioned stimulus to a conditioned stimulus through repeated presentation ‘there is established…a temporary relation between the activity of a certain organ and the phenomena of the external world (1928). He later presents that “if a new, formerly indifferent stimulus, entering into the cerebrum, meets in the nervous system at the moment, a focus of strong excitation, this newly arriving stimulation begins to concentrate, and to open a road, as it were, to this focus, and through it onward to the corresponding organ, becoming in this way a stimulator of that organ” (1928, p. 124).

This acquired response, known as the conditioned response (CR), demonstrated the process of classical conditioning.

Temporary Connection

A primary point is that these conditioned responses are temporary. For them to continue, they need continual reinforcement. A concept primary to later behaviorism theories. Over time, without reinforcement, the conditioned response weakens and then becomes extinct.

Excitation and Inhibition

While we mainly focus on the excitation of physiological states in connection to conditioned responses, Pavlov’s experiments also equally examined inhibitory reactions to stimuli. Just as experience can condition non-primary stimuli in the environment to excite reflexive responses, experience can also condtion non-primary stimuli to inhibit the excitation of reflexive responses. If food is presented, but a bitter substance given to the dog after presenting the food, soon the dog quits salivating at the presences of food. A brain creates a temporary connection between the food and the bitter taste.

Pavlov presented that “the inhibition of the conditioned reflex is observed also in the converse case When you have a combination of agents acting as a conditioned stimulus, in which, as has been already stated, one of the agents by itself produces almost no effect, then frequent repetition of the powerfully acting stimulus alone, without the other one, leads to a marked inhibition of its action, almost to the point of its annihilation” (1928, p. 92).

Pavlov explains, “one must simply state that all the highest nervous activity, as it manifests itself in the conditioned reflex, consists of a continual change of these three fundamental processes—excitation, inhibition, and disinhibition” (p. 128). Gregory Kimble wrote that “excitation and inhibition are so closely related in Pavlovian thought that there is little point in attempting to treat them separately” (Kimble, 1967).

Individual Differences

Typically, when we review research, such as Pavlov’s dog experiments we envision uniform responses, equally applicable to all the dogs. Behavior is never so easy. Every behavior is a complex intertwining of biological foundations and past learning. Each dog, just as individual human being, brought their own personality to the lab. These biological sensitivities strongly influenced the dogs conditioning and extinguishing of learned behavioral reactions.

Pavlov mentioned four personality types in the dogs. He refers to melancholic, phlegmatic, choleric, and sanguine personalities. The melancholic and phlegmatic he distinguished as inhibited in terms of movement. The choleric and sanguine groupings he described as inhibited. Inhibited and uninhibited translate well with extrovert-introvert personalities, similar to those dominated by the behavior activation system (BAS) compared to those dominated by the behavioral inhibition system (BIS).

Based upon these personality classifications, Pavlov found differences in the ways dogs reacted to stimuli and the rate of conditioning and extinguishing of behaviors. For instance, he found that the sanguine dogs were easier to excite salivatory response with a conditioned stimulus than it was to inhibit such a response. In contrast, Pavlov discovered that the melancholic animals were difficult to elicit a salivary response with a conditioned stimulus but once reinforcement was discontinued the stimulus quickly acquired the capacity to inhibit responses (Robinson, 2011).

The Significance of Pavlov’s Research

Pavlov’s groundbreaking findings challenged the prevailing belief that reflexes were solely innate. His work showed that animals are capable of forming conditioned responses through the association of stimuli. This discovery had far-reaching implications, not only for the field of psychology but also for understanding the mechanisms of learning and behavior.

Pavlov considers the organisms ability to adapt to environmental signals as a survival mechanism. He presented in one of his lectures that “these temporary relations and its law (reinforcement by repetition and weakening if not repeated) play an important role in the welfare and integrity of the organism, by means of it the fitness of the adaptation between the activity of the organism and the environment becomes more perfect” (1928).

Our bodies reflexively react to environmental cues, perhaps, relying on predictive coding, without exposure to the ultimate stimuli of our excitement. Basically, our repertoire of motivating stimuli expands through growing complex connections between stimuli in our environment and personal goals. These connections allow automatic processes to reflexively respond in preparation to perceived opportunity and threats. The advance warning system gives the organism a competitive advantage for survival.

Habits and Pavlovian (Classical) Conditioning

Jeremy Dean PhD., Author of is the founder and author of PsyBlog, wrote, “the bathroom, car, and coffee shop are like Pavlov’s bell, unconsciously reminding us of long-standing patterns of behavior, which we then enact again, in exactly the same way as before” (2013, Dean, Kindle location:166). Basically, environmental cues are neurotically connected to behaviors. This can work for or against our desired ending. Accordingly, constructing environments to nudge behaviors we desire can be an important component of successful change. Markedly, this is especially true when the desire is extinction of habitual behavioral responses.

Many habits stick because their connection to unconscious reflexes, responding to environmental cues. Accordingly, as long as we stay in the same environment, the cues will keep exciting internal processes to continue acting in ways we which we could stop.

Fear Learning

Lisa Feldman Barrett PhD., explains that ‘fear learning’ is just a fancy name for ‘classical conditioning.’ (Barrett, 2018, p. 271)

Steven Southwick and Dennis Charney explain that “the brain’s limbic system links the fear that accompanies a traumatic event to sights, sounds, odors, time of day, weather conditions, and other ordinarily neutral stimuli that are present during the frightening event. These contextual stimuli can then become fear-conditioned cues that are capable of triggering fear by themselves because of their previous association with danger” (Southwick & Charney, 2018, Kindle location: 2,110).

Joseph LeDoux. brain scientist who specializes in the neurobiology of fear, explains that “If an animal is lucky enough to survive one dangerous encounter, its brain should store as much about the experience as possible…” (Kindle location: 2,151). Certainly, when we view classical conditioning from this outside of the lab perspective, it is clear why this conditioning contributes to an organisms survivability. Consequently, it is also clear that when these conditioned responses go askew, such as in post-traumatic stress disorder, they can dramatically impact our lives.

A Few Words by Psychology Fanatic

Pavlov’s dog experiments remain a keystone in psychology, illustrating the principles of classical conditioning through simple to understand research. While psychology continues to expand in understanding and scope, the early principles so clearly presented by Pavlov remain. Accordingly, much of Pavlov’s early findings remain relevant to both the scientist, therapist and even for the lay person trying to adopt new behaviors or extinguish old habits.

We may all benefit from taking a few moments to mindfully examine and identify some of the classically conditioned responses ingrained into our lives. Perhaps, once we identify the conditioned responses, we may use the knowledge to improve our lives.

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Asratyan, Ezra.A. (2022) I.P. Pavlov. His Life and Work.

Barrett, Lisa Feldman (2018) How Emotions Are Made: The Secret Life of the Brain. Mariner Books; Illustrated edition.

Dean, Jeremy (2013). Making Habits, Breaking Habits: Why We Do things, Why We Don’t and How to Make any change Stick. Da Capo Lifelong Books; Illustrated edition.

Horsley, W. (1928) Lectures on Conditioned Reflexes Vol 1.

Kimble, Gregory (1967). Foundations of Conditioning and Learning. ‎Irvington Publishers.

Robinson, David L. (2011). Brain, Mind and Behaviour: A New Perspective on Human Nature. 

Southwick, Steven, Charney, Dennis (2018) Resilience: The Science of Mastering Life’s Greatest Challenges. Cambridge University Press; 2 edition.

Watson. John B. (1924/2012). Behaviorism. Forgotten Books.

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