Understanding Stimulus Discrimination in Psychology

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Stimulus discrimination is a term used in both classical and operant conditioning. It involves the ability to distinguish between one stimulus and similar stimuli. In both cases, it means responding only to certain stimuli, and not responding to those that are similar.

This article discusses how stimulus discrimination works, when it occurs, and how it can affect behavior. It also covers how it differs from stimulus generalization.

Discrimination in Classical Conditioning

Classical conditioning is a type of learning that involves forming associations between two stimuli. In this process, 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 a bell tone were the conditioned stimulus, discrimination would involve being able to tell the difference between the bell sound and other similar sounds.

Classical conditioning works like this:

  • Forming an association: A previously neutral stimulus, such as a sound, is paired with an unconditioned stimulus (UCS). The unconditioned stimulus represents something that naturally and automatically triggers a response. For example, the smell of food is an unconditioned stimulus, while salivating to the smell is an unconditioned response.
  • Responding to a conditioned stimulus: After an association has been formed between the previously neutral stimulus, now known as the conditioned stimulus (CS), and the unconditioned response, the CS can evoke the same response, now known as the conditioned response, even when the UCS is not present.

In Ivan Pavlov's classic experiments, the sound of a tone (a neutral stimulus that became a conditioned stimulus) was repeatedly paired with the presentation of food (unconditioned stimulus), which naturally and automatically led to a salivary response (unconditioned response).

Eventually, the dogs would salivate in response to the sound of the tone alone (a conditioned response to a conditioned stimulus). Now, imagine that Pavlov introduced a different sound to the experiment. Instead of presenting the sound of the tone, let's imagine that he sounded a trumpet. What would happen?

If the dogs did not drool in response to the trumpet noise, it meant that they were able to discriminate between the sound of the tone and the similar stimulus. Not just any noise will produce a conditioned response. Because of stimulus discrimination, only a very particular sound will lead to a conditioned response.


In classical conditioning, stimulus discrimination helps learners respond to a specific stimulus and not to other similar stimuli.

Examples of Stimulus Discrimination

In one well-known experiment on classical conditioning, researchers paired the taste of meat (unconditioned stimulus) with the sight of a circle (conditioned stimulus), and dogs learned to salivate in response to the presentation of a circle. The researchers found, however, that the dogs would also salivate when they saw an ellipse, an oval shape.

Over time, as the dogs experienced more and more trials where they did not experience the taste of meat upon seeing the ellipse, they eventually became able to discriminate between the two similar stimuli. They would salivate in response to the circle, but not when they saw the ellipse.

In consumer behavior, marketers use stimulus discrimination to help consumers recognize their products as distinct from similar products. For example, the packaging on a certain brand of snack cookies might help buyers discriminate between multiple similar products.

Discrimination in Operant Conditioning

Operant conditioning is a form of learning that relies on rewards and punishments to teach new behaviors. In operant conditioning, stimulus discrimination refers to responding only to the discriminative stimulus and not to similar stimuli.

For example, imagine that you have trained your dog to jump in the air whenever you say the command, "Jump!" In this instance, discrimination refers to your dog's ability to distinguish between the command for jumping and similar commands such as sit, stay, or speak.

Another example might be the type of behaviors that are appropriate in one situation but not in another. Because of stimulus discrimination, you recognize that eating with your hands with your elbows on the table might be appropriate in a casual, fast-food restaurant, but that such behavior would be considered inappropriate in a more formal dining setting.

Stimulus Discrimination vs. Stimulus Generalization

Stimulus discrimination can be contrasted with a similar phenomenon known as stimulus generalization. In classical conditioning, for example, stimulus generalization would involve being unable to distinguish between the conditioned stimulus and other similar stimuli.

In the famous Little Albert experiment, a young boy was conditioned to fear a white rat, but he displayed the fear response upon the presentation of similar white, furry objects.

An example of stimulus discrimination would have been if the little boy in the experiment had distinguished between the white rat and other white, furry objects.


Stimulus discrimination plays an important role in the learning process. Being able to discriminate between stimuli allows you to respond to the correct stimuli without generalizing the response to other stimuli.

Frequently Asked Questions

  • Is stimulus discrimination training effective?

    Stimulus discrimination training is a strategy that can be useful for teaching people to engage in behavior only in the presence of a certain stimulus. This may be helpful for teaching people to only respond with specific behaviors in certain settings or situations. It may also be helpful for minimizing anxiety and fear responses by reducing the generalization of the fear response.

  • What is stimulus control?

    Stimulus control refers to how much behavior is affected by various stimulus conditions. In operant conditioning, it can refer to when a subject behaves in a certain way in the presence of a specific stimulus but behaves in a different way when that stimulus is absent.

  • What are examples of stimulus discrimination in everyday life?

    Stimulus discrimination also occurs in real life outside of experimental lab settings. Only ordering a dish at one restaurant because you know that other restaurants don't offer that same menu item is an example of stimulus discrimination. Your cat being able to tell the difference between hearing you open a bag of chips and you opening a bag of cat treats is another example.

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