Classical conditioning is a type of unconscious learning. It occurs when a person or animal experiences an automatic response whenever they encounter a specific stimulus. Simply put, it is learning through association.

The most widely known example of classical conditioning is Pavlov’s dog.

The neurologist Ivan Pavlov observed that his dog began salivating at the sound of a bell ringing. This was because Pavlov repeatedly rang the bell just before giving the dog food, and the dog started associating the bell with the food. So, over time, the sound of the bell ringing on its own caused an automatic response, which, in this instance, was salivation.

This article explores how classical conditioning works, including its five principles and other examples. The article also discusses the differences between classical and operant conditioning, criticisms of classical conditioning, and classical conditioning in therapy.

A dog licking its lips 1Share on Pinterest
Catherine Falls Commercial/Getty Images

There are three stages of classical conditioning, and specific terms describe what is occurring in each stage.

Before conditioning

At this stage, the unconditioned stimulus (UCS) produces an unconditioned response (UCR) in a human or animal. For example, stomach flu may make someone feel nauseous, or food will make a dog salivate. In other words, the response is natural, and a person or animal has not learned any new behavior.

At the same time, there is also another type of stimulus — a neutral stimulus (NS), but a person or animal will not respond to it until it occurs with the UCS. Using the example of Pavlov’s dog, the NS was the bell before Pavlov paired it with the food (UCS).

During conditioning

At this stage, the NS pairs with the UCS. Consequently, the NS becomes a conditioned stimulus (CS) over repeated pairings.

With Pavlov’s dog, Pavlov rang the bell (NS) before presenting the food (UCS), which caused salivation (UCR). Conditioning is more likely to occur when the CS (bell) occurs just before the UCS (food), not the other way around. For example, Pavlov rings the bell just before presenting the food to the dog, not after.

After conditioning

When a person or animal becomes conditioned, they associate the CS (bell) with the UCS (food) to create a new conditioned response (CR). So going back to Pavlov’s dog, at this stage, the dog will salivate after hearing the bell ring, even when no food is presented with the bell.

The five principles of classical conditioning are below.


During the initial period of learning, a person or animal experiences acquisition. When this happens, the person or animal begins to pair an NS with a UCS. Using Pavlov’s dog as an example, the bell (NS) must ring before the presentation of food (UCS).


Extinction occurs when the UCS (the food) and CS (the bell) are no longer presented together. Consequently, the CR, which is the salivation after ringing the bell, no longer occurs. The connection between the bell and food has broken down, and the learned association is lost.

Spontaneous recovery

After extinction, a spontaneous recovery may occur. This means the connection between the bell (CS) and the food (UCS) recovers after a brief period of rest — Pavlov noticed this in his dogs. When he finished extinction training and gave the dogs 2 hours of rest, they began to salivate again after hearing the bell ringing.


Generalization happens when a person or animal responds to stimuli similar to the CS. For example, Pavlov’s dog may begin to salivate to a sound similar to the bell ringing. The sound, for example, could be a bicycle bell, which sounds slightly different but is similar enough to produce the CR, which, in this case, is salivating.


When an animal or human can discriminate between stimuli, they can tell the difference between them. Using Pavlov’s dog as an example, the dog would only respond to the sound of a specific bell. This means if the canine heard a different type of bell ringing, they would not salivate.

Classical conditioning may play a role in the development of substance use disorder and fear.

Substance use

People who often smoke or drink alcohol while socializing may associate social environments with the dopamine rush from consuming these substances.

Smoking cigarettes, for example, is the UCS, and the dopamine rush is the UCR. Socializing is the NS, which, over time, becomes the CS. In these instances, the social environments become cues for smoking or drinking alcohol.


In 1920, scientists conditioned an 11-month-old infant to fear a white rat. They did this by making a loud noise with a metal bar every time they let the child play with the rat. The infant began to fear other white fluffy objects, including a rabbit and a white fur coat. This suggests the CR (fear) was generalizable to additional similar stimuli.

However, people need to note that healthcare professionals now consider this study unethical.

With classical conditioning, a person learns to respond to a stimulus that is associated with a response. Pavlov’s dogs, for example, associated the ringing of a bell with food and salivated when they heard it.

Operant conditioning, on the other hand, is consequence-based. Positive reinforcement, or a reward when completing a task, encourages an animal or human to complete or repeat that task or behavior. Negative reinforcement does the opposite and reduces the likelihood of a person or animal repeating that behavior.

Healthcare professionals may use counterconditioning techniques in behavioral therapy.

Examples include aversion therapy and systematic desensitization. A mental health professional may use these types of therapies to help treat phobias and anxiety.

They do this by slowly introducing someone to the stimulus that induces their fear or anxiety response. The goal is that, over time, their behavior and thought processes toward the stimulus will change, and they will no longer feel fear or anxiety due to the stimulus.

Classical conditioning occurs when a person or animal associates a specific stimulus with a response. Some responses to stimuli are unconditioned and natural.

However, if one stimulus occurs just before another, a person or animal may also begin to associate it with the response. When this happens, the neutral stimulus becomes a conditioned stimulus and can elicit a response on its own.

Pavlov demonstrated this with dogs. He rang a bell just before he presented them with food, and over time, the dogs associated the bell with food and salivated when they heard it.

Classical conditioning may play a role in the development of phobias and substance use disorders. Healthcare professionals may use counterconditioning techniques in behavioral therapies to help treat phobias and other mental health conditions.