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What is Classical Conditioning?

Discovered by the Russian physiologist Ivan Pavlov, classical conditioning is a type of unconscious or automatic learning. This learning process creates a conditioned response through associations between an unconditioned stimulus and a neutral stimulus.

In other words, classical conditioning consists of placing a neutral stimulus in front of a naturally occurring reflex. In Pavlov’s classical experiment with dogs, the neutral cue was the sound of a tone and the natural reflex was salivation in response to food. By associating the neutral stimulus (the sound) with the unconditioned stimulus (the food), the sound of the tone alone could produce the salivation response.

Although classical conditioning was not discovered by a psychologist, it has had an enormous influence on the school of thought in psychology known as behaviorism. Behaviorism assumes that all learning occurs through interactions with the environment and that the environment shapes behavior.

El condicionamiento clásico explica algunos tipos de aprendizajes en seres humanos y otros animales.

Classical conditioning-also sometimes called Pavlovian conditioning-uses a few different terms to help explain the learning process. Here are the terms you should know about classical conditioning.

Neutral stimulus

A neutral stimulus is a stimulus that does not initially elicit a response by itself. If you see a beach ball in the sand, for example, it will not necessarily elicit a response. That would make it a neutral stimulus.

Conditioned stimulus

A conditioned stimulus is a stimulus that was previously neutral (did not trigger a response) but now leads to a response. If you used to pay no attention to a passing dog until you were bitten by one, and now it makes you feel afraid every time you see a dog, the dog has become a conditioned stimulus.

Unconditioned response

An unconditioned response is an automatic response or a response that occurs without thinking when an unconditioned stimulus is present. If you smell your favorite food and your mouth waters, watering is an unconditioned response.

Conditioned response

A conditioned response is a learned response or a response that is created where no response existed before. Going back to the example of being bitten by a passing dog, which now makes you feel fear every time you see one, the fear you have begun to experience is a conditioned response.

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To better understand how classical conditioning works, it is important to become familiar with the basic principles of the process. Classical conditioning involves the formation of an association between two stimuli, which results in a learned response.

This process consists of three basic phases.

Phase 1: Before conditioning

The first part of the classical conditioning process requires a natural stimulus that automatically elicits a response. Salivation in response to the smell of food is a good example of a natural stimulus.

During this phase of the process, the unconditioned stimulus (EIC) results in an unconditioned response (RIC). For example, presenting food (the EIC) naturally and automatically triggers a salivation response (the RIC).

At this point, there is also a neutral stimulus that produces no effect, yet. It is not until the neutral stimulus is paired with the UCS that it comes to evoke a response.

Let’s look in more detail at the two critical components of this phase of classical conditioning:

  • The unconditioned stimulus is one that triggers a response unconditionally, naturally and automatically. For example, when you smell one of your favorite foods, you may immediately feel very hungry. In this example, the smell of the food is the unconditioned stimulus.
  • The unconditioned response is the unlearned response that occurs naturally in response to the unconditioned stimulus. In our example, the sensation of hunger in response to the smell of food is the unconditioned response.

In the preconditioning phase, an unconditioned stimulus is paired with an unconditioned response. A neutral stimulus is then introduced.

Phase 2: During conditioning

During the second phase of the classical conditioning process, the previously neutral stimulus is repeatedly paired with the unconditioned stimulus. As a result of this pairing, an association is formed between the previously neutral stimulus and the UCS.

At this point, the previously neutral stimulus becomes known as the conditioned stimulus (CS). The subject has been conditioned to respond to this stimulus. The conditioned stimulus is a previously neutral stimulus that, after being associated with the unconditioned stimulus, eventually triggers a conditioned response.

In our previous example, suppose that while smelling your favorite food, you also heard the sound of a whistle. Although the whistle is not related to the smell of the food, if the sound of the whistle were paired several times with the smell, the sound of the whistle would end up triggering the conditioned response. In this case, the sound of the whistle is the conditioned stimulus.

The during conditioning phase involves the pairing of a neutral stimulus with an unconditioned stimulus. Finally, the neutral stimulus becomes the conditioned stimulus.

Phase 3: After conditioning

Once the association between the UCS and the CS has been established, the presentation of the conditioned stimulus alone will come to evoke a response, even without the unconditioned stimulus. The resulting response is known as the conditioned response (CR).

The conditioned response is the learned response to the previously neutral stimulus. In our example, the conditioned response would be to feel hungry at the sound of the whistle.

In the post-conditioning phase, the conditioned stimulus alone triggers the conditioned response.

Behaviorists have described a number of different phenomena associated with classical conditioning. Some of these elements involve the initial establishment of the response, while others describe the disappearance of a response. These elements are important for understanding the process of classical conditioning.

Let’s take a look at five key principles of classical conditioning.


Acquisition is the initial phase of learning in which a response is first established and gradually reinforced. During the acquisition phase of classical conditioning, a neutral stimulus is repeatedly paired with an unconditioned stimulus.

As will be recalled, an unconditioned stimulus is something that triggers a response naturally and automatically without any learning. Once the association has been made, the subject will begin to emit a behavior in response to the previously neutral stimulus, which is now known as a conditioned stimulus. It is at this point that we can say that the response has been acquired.

For example, imagine you are conditioning a dog to salivate in response to the sound of a bell. You repeatedly pair the presentation of food with the sound of the bell. You can tell that the response has been acquired as soon as the dog begins to salivate in response to the sound of the bell.

Once the response is established, you can gradually reinforce the salivation response to ensure that the behavior is well learned.


Extinction occurs when the occurrences of a conditioned response decrease or disappear. In classical conditioning, this occurs when a conditioned stimulus is no longer paired with an unconditioned stimulus.

For example, if the smell of food (the unconditioned stimulus) were paired with the sound of a whistle (the conditioned stimulus), the sound of the whistle would eventually evoke the conditioned response of hunger.

However, if the unconditioned stimulus (the smell of food) were no longer paired with the conditioned stimulus (the whistle), the conditioned response (hunger) would eventually disappear.

Spontaneous recovery

Sometimes a learned response can suddenly reappear, even after a period of extinction. Spontaneous recovery is the reappearance of the conditioned response after a period of rest or a decrease in the response.

For example, imagine that after training a dog to salivate at the sound of a bell, you stop reinforcing the behavior and the response eventually dies out. After a rest period during which the conditioned stimulus is not presented, you suddenly ring the bell and the animal spontaneously recovers the previously learned response.

If the conditioned stimulus and the unconditioned stimulus are no longer associated, extinction will occur very quickly after spontaneous recovery.


Stimulus generalization is the tendency of a conditioned stimulus to evoke similar responses after the response has been conditioned.8 For example, if a dog has been conditioned to salivate at the sound of a bell, the animal may also show the same response to stimuli similar to the conditioned stimulus.

In John B. Watson’s famous Little Albert Experiment, for example, a small boy was conditioned to fear a white rat. The child demonstrated generalization of the stimulus by also showing fear in response to other fuzzy white objects, including stuffed toys and Watson’s own hair.


Discrimination is the ability to differentiate between a conditioned stimulus and other stimuli that have not been paired with an unconditioned stimulus.

For example, if the conditioned stimulus were a bell tone, discrimination would consist of being able to differentiate the bell tone from other similar sounds. Since the subject is able to distinguish between these stimuli, he will only respond when the conditioned stimulus is presented.

It may be useful to look at some examples of how the classical conditioning process works in both experimental and real-world settings.

Fear response

The experiment of John B. Watson with little Albert is a perfect example of the fear response. The child initially showed no fear of a white rat, but after the rat was repeatedly paired with loud, frightening sounds, the child cried when the rat was present. The child’s fear also generalized to other white fuzzy objects.

Before conditioning, the white rat was a neutral stimulus. The unconditioned stimulus was loud, booming sounds, and the unconditioned response was the fear response created by the noise.

By repeatedly pairing the rat with the unconditioned stimulus, the white rat (now the conditioned stimulus) came to evoke the fear response (now the conditioned response).

This experiment illustrates how phobias can be formed through classical conditioning. In many cases, a single pairing of a neutral stimulus (a dog, for example) and a frightening experience (being bitten by the dog) can lead to a lasting phobia (being afraid of dogs).

Taste aversion

Another example of classical conditioning is the development of conditioned taste aversions. Researchers John Garcia and Bob Koelling became aware of this phenomenon when they observed how rats that had been exposed to nausea-inducing radiation developed an aversion to flavored water after the radiation and water were presented together.

In this example, radiation represents the unconditioned stimulus and nausea the unconditioned response. After pairing the two, the scented water is the conditioned stimulus, while the nausea that formed upon exposure to water alone is the conditioned response.

Further research showed that these classically conditioned aversions could be produced by a unique pairing of the conditioned stimulus and the unconditioned stimulus.

The researchers also found that such aversions can even develop if the conditioned stimulus (the taste of the food) is presented several hours before the unconditioned stimulus (the nausea-provoking stimulus).

why do these associations develop so quickly? The formation of such associations can be beneficial to the survival of the organism. If an animal eats something that makes it sick, it needs to avoid eating the same food in the future to avoid illness or even death.

This is a great example of what is known as biological priming. Some associations form more easily because they aid survival.

Ismael Abogado

Ismael Abogado

Psychologist and constant learner of the mind and soul.

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