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Neutral Stiimulus

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Unconditioned Stimulus

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Continuous Associations

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Neutral Stimulus becomes Conditioned Stimulus

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Ivan Pavlov (1849-1936)


What happens when you see a commercial of a Polar Bear skating gracefully around an outdoor ice rink? Can you imagine him holding something? Do you by chance think of a bottle of ‘Coca-Cola’? How about when you’re watching a Coca-Cola commercial with Christmas music, holiday lights and that red lit-up Coke truck riding down a snowy, moonlit background? For some, this scenario can bring about feelings of joy and happiness.

And this is the exact reaction the executives of Coca-Cola are looking for. They want you to associate festive happiness with their product.  They have used a well-known theory called Classical Conditioning and the founding scientist of this theory is Ivan Pavlov, one of the most brilliant and dedicated founders in the psychology field of all time.

Ivan Pavlov, a Russian born physiologist, had a strong family background in theology.  His father was a priest and his grandfather was a sexton, which is the person that keeps the church and maintains it in good condition. His family was not wealthy, and he learned the appreciation of hard work, a factor that may have led him to his unequivocal dedication to research.  Pavlov, himself, was also enrolled in seminary school preparing to become a priest.  His seminary teachers left a positive impression on him with their devotion and dedication.  A trait he was able to transfer onto his future career in science.  Pavlov’s road to becoming a seminary himself did not last however as his love for science prevailed and he left theology behind to become a physiologist. 

Following this path he earned an extensive list of accomplishments from winning a gold medal for his contributions on the work of The Physiology of the Pancreatic Nerves, to earning a degree in Natural Sciences, and from earning another gold medal from The Academy of Medical Surgery to being awarded with several honorariums in the physiology and science fields.  He was the Director for the Department of Physiology at the Institute of Experimental Medicine until his death for over 45 years and brought the institute into the highest status of physiological research to date.  He was made Professor of Pharmacology at the Military Medical Academy and appointed Chair of Physiology for 30 years.

And perhaps one of his most notable accomplishments was receiving the Nobel Prize for his work on the Physiology of Digestive Glands.

This brings us to one of the most famous discoveries of all time, Classical Conditioning, or also known as Pavlovian Conditioning, a reflexive type of learning which ultimately led him to winning his Nobel. 

Pavlov had a love of natural science and physiology; he held the strong belief that physiology was behind human behavior.  His famous study which came to be known as ‘Pavlov’s Dogs’, was happened upon accidentally, which ultimately tends to be the case in many discoveries, while he was studying the digestive tracts of dogs.  He noticed that the dogs would salivate upon the expectation of food or while the food was being prepared.  He formulated a hypothesis that the dogs could be conditioned to have the same instinctual salivating response to a non-food related item. In other words, he could condition the dogs to salivate over a sound alone, and to prove his theory of subconscious instinctual or reflexive learning.

Pavlov used a device that measured the amount of saliva the dogs produced while being presented with food.  The device consisted of a tube connected from the dogs’ mouth to a container that measured the amount of drops produced and a revolving drum for recording the measurements.  Very scientific in the late 1800’s! 

While being presented with food routinely, the dogs would invariably salivate each and every time.  In fact, they began to salivate with the opening of the door to which the food was arriving from.  From there, Pavlov introduced a bell.  He would ring the bell each time he presented the food.  The bell, of course, would not cause the dogs to salivate on its own, however, in time Pavlov was able to create a physiological reaction in the dogs to the sound of the bell alone.  The dogs salivated when they heard the bell tone, even without the presentation of food.  This was a remarkable accomplishment.    

Classical Conditioning:

Pavlov’s First Order Conditioning

The terminology behind this study is just as important as the results;

Before Conditioning

Food                                                                           Salivation

Unconditioned Stimulus (CS)                                 Unconditioned Response (UR)


Neutral Stimulus (NS)                                             No response

Food + Bell                                                                Salivation

Unconditioned Stimulus (US)                                 Unconditioned Response (UR)

            Plus Neutral Stimulus (NS)

After Conditioning

Bell                                                                              Salivation

Conditioned Stimulus (CS)                                     Conditioned Response (CR)


Pavlov was able to produce a conditioned response from the tone of the bell alone, which was previously a neutral stimulus.  After presenting the food with the bell several times, the dogs would associate the tone of the bell with the food, and thus, would produce a high level of salivation upon hearing the tone.  However, timing is very critical to elicit this reaction.  The bell or (Neutral Stimulus) must be rung within a close time frame to the presentation of food or (Unconditioned Stimulus) for the association to work.

Pavlov’s Second Order Conditioning

Second Order Conditioning occurs when a neutral stimulus is paired with a conditioned stimulus simultaneously together until both stimuli produce a conditioned response.  For example; Add a light to the bell with the presentation of food, eventually the light alone will elicit the same physiological response in the dogs as the bell had.

Stimulus Generalization in classical conditioning is the process of when a subject is exposed to an object that is similar to the conditioned stimulus, and has the same conditioned response.  For example, a completely different type of bell tone from the original one could elicit a conditioned response in the same manner. 

Stimulus Discrimination in classical conditioning is the process by which the subject is exposed to a completely different bell tone, and each time they are NOT presented with the unconditioned stimulus (dog food), but the original bell is still presented with the unconditioned stimulus (dog food), resulting in discrimination of the differentiated tones.  And therefore, the subject will not have the conditioned response to the second bell. 

Extinction is part of Pavlov’s Classical Conditioning as well, which is the process of weakening the conditioned response until it no longer exists by continually pairing the conditioned stimulus (bell) without the unconditioned stimulus (dog food).

Classical Conditioning can be used in real-life circumstances as well.  It has been used to fight addiction, such as smoking with the use of a prescription medication called Varenicline that, along with physiological effects in the brain, has been known to promote ‘condition taste aversion’ to cigarettes.  In classical conditioning, the Varenicline promotes nausea immediately upon smoking, and eventually if used correctly and often, the subject can then have an unpleasant conditioned response, such as nausea with just the site of a cigarette. 

As you see, this theory can easily be applied to learning and behavior in real-life situations such as kicking addiction, and will be used for many more years including the Coca-Cola commercials we’ve grown to love.

It is easy to see what a huge and important contribution Ivan Pavlov has made to not only physiology,  but to psychology as well.  His work has earned him many accolades and brought forth changes in learning and behavior that still exist today.  


  7. Pavlovian conditioning. By: Sparzo, Frank J., Salem Press Encyclopedia of Health, January, 2014
  10. Psychology 101 Second Edition (Wade, Tavris, Saucier, Elias) Pearson, Prentice, Hill, (2006)


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