What Is Classical Conditioning?

A Learning Process Discovered by Ivan Pavlov

Cropped Hand Of Man Feeding Dog

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Classical conditioning is a behaviorist theory of learning. It posits that when a naturally occurring stimulus and an environmental stimulus are repeatedly paired, the environmental stimulus will eventually elicit a similar response to the natural stimulus. The most famous studies associated with classical conditioning are Russian physiologist Ivan Pavlov’s experiments with dogs.

Key Takeaways: Classical Conditioning

  • Classical conditioning is the process by which a naturally occurring stimulus is paired with a stimulus in the environment, and as a result, the environmental stimulus eventually elicits the same response as the natural stimulus.
  • Classical conditioning was discovered by Ivan Pavlov, a Russian physiologist, who conducted a series of classic experiments with dogs.
  • Classical conditioning was embraced by the branch of psychology known as behaviorism.

Origins and Influence

Pavlov’s discovery of classical conditioning arose out of his observations of his dogs’ salivation responses. While dogs naturally salivate when food touches their tongues, Pavlov noticed that his dogs' salivation extended beyond that innate response. They salivated when they saw him approach with food or even just heard his footsteps. In other words, stimuli that had previously been neutral became conditioned because of their repeated association with a natural response.

Although Pavlov wasn’t a psychologist, and in fact believed his work on classical conditioning was physiological, his discovery had a major influence on psychology. In particular, Pavlov’s work was popularized in psychology by John B. Watson. Watson kicked off the behaviorist movement in psychology in 1913 with a manifesto that said psychology should abandon the study of things like consciousness and only study observable behavior, including stimuli and responses. After discovering Pavlov’s experiments a year later, Watson made classical conditioning the foundation of his ideas.

Pavlov’s Experiments

Classical conditioning requires placing a neutral stimulus immediately before a stimulus that automatically occurs, which eventually leads to a learned response to the formerly neutral stimulus. In Pavlov’s experiments, he presented food to a dog while shining a light in a dark room or ringing a bell. The dog automatically salivated when the food was placed in its mouth. After the presentation of the food was repeatedly paired with the light or bell, the dog started salivating when it saw the light or heard the bell, even when no food was presented. In other words, the dog was conditioned to associate the previously neutral stimulus with the salivation response.

Types of Stimuli and Responses

Each of the stimuli and responses in classical conditioning is referred to by specific terms that can be illustrated with reference to Pavlov’s experiments.

  • The presentation of food to the dog is referred to as the unconditioned stimulus (UCS) because the dog’s response to the food occurs naturally.
  • The light or bell is the conditioned stimulus (CS) because the dog must learn to associate it with the desired response.
  • Salivation in response to the food is called the unconditioned response (UCR) because it’s an innate reflex.
  • Salivation to the light or bell is the conditioned response (CR) because the dog learns to associate that response with the conditioned stimulus.

The Three Stages of Classical Conditioning

The process of classical conditioning occurs in three basic stages:

Before Conditioning

At this stage, the UCS and CS have no relationship. The UCS comes up in the environment and naturally elicits a UCR. The UCR wasn’t taught or learned, it’s a completely innate reaction. For example, the first time a person takes a ride on a boat (UCS) they may become seasick (UCR). At this point, the CS is a neutral stimulus (NS). It has yet to produce any kind of response because it hasn’t been conditioned yet.

During Conditioning

During the second stage, the UCS and NS are paired leading the previously neutral stimulus to become a CS. The CS occurs just before or at the same time as the UCS and in the process the CS becomes associated with UCS and, by extension, the UCR. Generally, the UCS and CS must be paired several times in order to reinforce the association between the two stimuli. However, there are times when this isn’t necessary. For example, if an individual gets sick once after eating a specific food, that food may continue to make them nauseous in the future. So, if the individual on the boat drank fruit punch (CS) right before getting sick (UCR), they could learn to associate fruit punch (CS) with feeling ill (CR).

After Conditioning

Once the UCS and CS have been associated, the CS will trigger a response without the need to present the UCS with it. The CS now elicits the CR. The individual has learned to associate a specific response with a previously neutral stimulus. Thus, the individual who got seasick may find that in the future fruit punch (CS) makes them feel ill (CR), despite the fact that the fruit punch really had nothing to do with the individual getting sick on the boat.

Other Principles of Classical Conditioning

There are several additional principles in classical conditioning that further detail how the process works. These principles include the following:


As its name suggests, extinction happens when a conditioned stimulus is no longer associated with an unconditioned stimulus leading to a decrease or complete disappearance of the conditioned response.

For example, Pavlov’s dogs started to salivate in response to the sound of a bell after the sound was paired with food over several trials. However, if the bell was sounded several times without the food, over time the dog’s salivation would decrease and eventually stop.

Spontaneous Recovery

Even after extinction has occurred, the conditioned response may not be gone forever. Sometimes spontaneous recovery happens in which the response reemerges after a period of extinction.

For example, suppose after extinguishing a dog’s conditioned response of salivation to a bell, the bell isn’t sounded for a period of time. If the bell is then sounded after that break, the dog will salivate again — a spontaneous recovery of the conditioned response. If the conditioned and unconditioned stimuli aren’t paired again, though, spontaneous recovery won’t last long and extinction will again occur.

Stimulus Generalization

Stimulus generalization happens when, after a stimulus has been conditioned to a specific response, other stimuli that may be associated with the conditioned stimulus also elicit the conditioned response. The additional stimuli are not conditioned but are similar to the conditioned stimulus, leading to generalization. So, if a dog is conditioned to salivate to the tone of a bell, the dog will also salivate to other bell tones. Although the conditioned response may not occur if the tone is too dissimilar to the conditioned stimulus.

Stimulus Discrimination

Stimulus generalization often doesn’t last. Over time, stimulus discrimination begins to occur in which stimuli are differentiated and only the conditioned stimulus and possibly stimuli that are very similar elicit the conditioned response. So, if a dog continues to hear different bell tones, over time the dog will start to distinguish between the tones and will only salivate to the conditioned tone and ones that sound almost like it. 

Higher-Order Conditioning

In his experiments, Pavlov demonstrated that after he has conditioned a dog to respond to a particular stimulus, he could pair the conditioned stimulus with a neutral stimulus and extend the conditioned response to the new stimulus. This is called second-order-conditioning. For example, after a dog was conditioned to salivate to a bell, the bell was presented with a black square. After several trials, the black square could elicit salivation by itself. While Pavlov found he could also establish third-order-conditioning in his research, he was unable to extend higher-order conditioning beyond that point.

Examples of Classical Conditioning

Examples of classical conditioning can be observed in the real world. One instance is various forms of drug addiction. If a drug is repeatedly taken in specific circumstances (say, a specific location), the user may become used to the substance in that context and require more of it to get the same effect, called tolerance. However, if the individual takes the drug in a different environmental context, the individual may overdose. This is because the user’s typical environment has become a conditioned stimulus that prepares the body for a conditioned response to the drug. In the absence of this conditioning, the body may not be adequately prepared for the drug.

A more positive example of classical conditioning is its use to support wildlife conservation efforts. Lions in Africa were conditioned to dislike the taste of beef in order to keep them from preying on cattle and coming into conflict with farmers because of it. Eight lions were given beef treated with a deworming agent that gave them indigestion. After doing this several times, the lions developed an aversion to meat, even if it wasn’t treated with the deworming agent. Given their aversion to the meat, these lions would be highly unlikely to prey on cattle.

Classical conditioning can also be used in therapy and the classroom. For example, to combat anxieties and phobias such as a fear of spiders, a therapist might repeatedly show an individual an image of a spider while they are performing relaxation techniques so the individual can form an association between spiders and relaxation. Similarly, if a teacher couples a subject that makes students nervous, like math, with a pleasant and positive environment, the student will learn to feel more positive about math.

Concept Critiques

While there are numerous real-world applications for classical conditioning, the concept has been criticized for several reasons. First, classical conditioning has been accused of being deterministic because it ignores the role of free will in people's behavioral responses. Classical conditioning anticipates an individual will respond to a conditioned stimulus with no variation. This may help psychologists predict human behavior, but it underestimates individual differences.

Classical conditioning has also been criticized for emphasizing learning from the environment and therefore championing nurture over nature. The behaviorists were committed to only describing what they could observe so they would stay away from any speculation about the influence of biology on behavior. Yet, human behavior is likely more complex than simply what can be observed in the environment.

A final criticism of classical conditioning is that it is reductionist. Although classical conditioning is certainly scientific because it utilizes controlled experiments to arrive at its conclusions, it also breaks down complex behaviors into small units made up of a single stimulus and response. This can lead to explanations of behavior that are incomplete.  


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Vinney, Cynthia. "What Is Classical Conditioning?" ThoughtCo, Aug. 28, 2020, thoughtco.com/classical-conditioning-definition-examples-4424672. Vinney, Cynthia. (2020, August 28). What Is Classical Conditioning? Retrieved from https://www.thoughtco.com/classical-conditioning-definition-examples-4424672 Vinney, Cynthia. "What Is Classical Conditioning?" ThoughtCo. https://www.thoughtco.com/classical-conditioning-definition-examples-4424672 (accessed April 23, 2021).