Conditioned Stimulus in Classical Conditioning

The conditioned stimulus is a previously neutral stimulus that eventually triggers a conditioned response. To do this the conditioned stimulus must first become associated with the unconditioned stimulus. It is a key part of the classical conditioning process.

Classical conditioning is an approach to learning first described by the Russian physiologist Ivan Pavlov. Pavlov was researching the digestive systems of dogs when he discovered that pairing a stimulus with something that already triggered a natural response could cause the neutral stimulus to start triggering the same response.

This discovery played an important role in the development of behaviorism, an approach to psychology that emphasize the role that learning and the environment play in human behavior.

How Does Conditioned Stimulus Work?

Ivan Pavlov first discovered the process of classical conditioning in his experiments on the digestive response of dogs. He noticed that the dogs naturally salivated in response to food, but that the animals also began to drool whenever they saw the white coat of the lab assistant who delivered the food.

The previously neutral stimulus (the lab assistant) had become associated with an unconditioned stimulus (the food) that naturally and automatically triggered a response (salivating).

The Conditioned Stimulus in Classical Conditioning

Classical conditioning takes place in three key stages:

• Acquisition: The association between the unconditioned stimulus and the neutral stimulus is first made during acquisition. The two are repeatedly paired until the neutral stimulus begins to elicit a response. In other words, the neutral stimulus becomes a conditioned stimulus during the acquisition stage.
• Extinction: During extinction, the conditioned stimulus is no longer paired with the unconditioned stimulus. As a result, the conditioned response may eventually disappear.
• Spontaneous recovery: During spontaneous recovery, a previously extinct response might suddenly reappear. 

Generalization and Discrimination

A few factors might affect how a conditioned stimulus evokes a behavior. Sometimes, generalization can occur. This happens when an organism responds to something similar to the conditioned stimulus.

For example, if a dog was conditioned to respond to a certain bell tone, they might generalize it to other sounds. As a result, they would produce the same response when they hear those different sounds.

Discrimination involves being able to distinguish between the conditioned stimulus and similar stimuli. This means the organism will only respond to the conditioned stimulus and not similar stimuli.

Example of the Conditioned Stimulus

Suppose that the smell of food is an unconditioned stimulus and a feeling of hunger is the unconditioned response. Now, imagine that when you smelled your favorite food, you also heard the sound of a whistle.

While the whistle is unrelated to the smell of the food, if the sound of the whistle was paired multiple times with the smell, the sound alone would eventually trigger the conditioned response. In this case, the sound of the whistle is the conditioned stimulus.

The example above is very similar to the original experiment Pavlov performed. The dogs in his experiment would salivate in response to food, but after repeatedly pairing the presentation of food with the sound of a bell, the dogs would begin to salivate to the sound alone. In this example, the sound of the bell was the conditioned stimulus.

More Examples of the Conditioned Stimulus

There are plenty of examples of how neutral stimuli can become a conditioned stimulus through association with an unconditioned stimulus. Let's explore a few more examples.

Food Followed by Illness

You eat a burrito for lunch but become ill shortly after. While the food you ate was previously a neutral stimulus, it becomes a conditioned stimulus through its association with the unconditioned stimulus (illness). As a result, you may develop a taste aversion in which just the idea of eating that same food again causes you to feel ill.

Dog Attack

You are out riding your bike one day and are attacked by a dog. Now, the place where you were attacked has become a conditioned stimulus and you experience fear every time you pass that spot.

Hotel Bell

A hotel concierge begins to respond every time he hears the ringing of a bell. Because the bell has become associated with the sight of customers needing assistance, the bell has become a conditioned stimulus.

Lunch Bell

Students hear the sound of a bell right before they are released for lunch. Eventually, just the sound of the bell alone causes the students to become hungry.