What Is Stimulus Generalization?

In psychology, stimulus generalization refers to the tendency for a conditioned response to be elicited by stimuli similar to the original conditioned stimulus. This phenomenon occurs when an organism responds to new stimuli that are similar but not identical to the stimulus that was originally conditioned.

Stimulus generalization occurs when an organism responds to a stimulus in the same way that it responds to a similar stimulus. This happens during the classical conditioning or operant conditioning process.

For example, imagine a dog being conditioned to run to its owner when it hears a whistle. The dog responds similarly when it hears a small child emit a high-pitched shriek. This is an example of stimulus generalization. The animal responds to a similar stimulus in the same way it would to the conditioned stimulus.

How Stimulus Generalization Works

Stimulus generalization works through a process where an organism transfers a learned response from the original conditioned stimulus to other stimuli that are similar. Here’s a detailed explanation of how it operates:

Initial Conditioning Phase

• Neutral Stimulus (NS): An initially neutral stimulus, which does not elicit the target response on its own, is introduced.
• Unconditioned Stimulus (US): This is a stimulus that naturally and automatically triggers a response without any prior learning (e.g., food causing salivation in dogs).
• Unconditioned Response (UR): This is the natural response to the unconditioned stimulus (e.g., salivation in response to food).

During the conditioning process, the neutral stimulus is repeatedly paired with the unconditioned stimulus until the neutral stimulus alone begins to elicit the response. At this point, the neutral stimulus becomes a conditioned stimulus (CS), and the response it elicits is the conditioned response (CR)

Generalization Phase

• Exposure to Similar Stimuli: After the conditioned response is established, the organism is exposed to stimuli that are similar to the conditioned stimulus. These similar stimuli are not identical to the original conditioned stimulus but share some characteristics with it.
• Response to Similar Stimuli: The organism begins to exhibit the conditioned response to these new, similar stimuli. The degree of response typically correlates with the similarity between the new stimuli and the original conditioned stimulus.

Examples of Stimulus Generalization

To understand how stimulus generalization works in psychology, it can be helpful to look at a few different examples.

The Little Albert Experiment

One of the most famous examples of stimulus generalization occurred in an early psychology experiment. In the Little Albert experiment, the behaviorist John B. Watson and his assistant Rosalie Rayner conditioned a little boy to fear a white rat.

However, the boy would respond similarly when he saw similar items, such as a furry white toy and Watson’s white beard.

Pavlov’s Dogs

Ivan Pavlov’s famous experiment with dogs also demonstrated the effects of stimulus generalization. While studying dogs’ digestive systems, Pavlov realized that pairing the sound of a bell with the presentation of food would condition the dogs to salivate whenever they heard the bell.

When other similar-sounding noises were presented, the dogs would also salivate in response. In this example of stimulus generalization, the dogs generalized the conditioned stimulus (the sound of the bell) onto other similar high-pitched sounds.

Phobias

Specific phobias can also be affected by stimulus generalization. For example, imagine that a dog bites a person and develops a phobia of dogs. They then experience fear responses whenever they see any small, furry, four-legged animal.

In this case, stimulus generalization has caused animals similar to a dog to trigger the same fear response.

Conditioned Food Aversions

Conditioned food aversions happen when someone develops an association between a food and getting sick (even if the food was not the source of the illness). After a single pairing of eating a food and becoming ill, people may avoid that food in the future.

Stimulus generalization might cause a person to avoid foods similar to the items they ate before getting sick. For example, if they became ill after eating a burrito, they might avoid eating burritos in the future, along with other foods wrapped in tortillas.

Factors That Influence Stimulus Generalization

• Similarity: The more similar the new stimulus is to the original conditioned stimulus, the stronger the generalized response.
• Experience: With more conditioning and exposure, organisms may learn to discriminate between the conditioned stimulus and similar stimuli, reducing generalization.
• Context: The environment in which the stimuli are presented can affect the degree of generalization. A familiar context might enhance generalization, while a novel context might reduce it.

The Impact of Stimulus Generalization

Stimulus generalization can have an impact on how people respond to different stimuli. For example, imagine in school that children are expected to line up for lunch when they hear the ding of a bell.

However, another similar-sounding bell also rings when the kids are expected to sit at their desks for reading time.

If stimulus generalization occurs, the children will have trouble determining which response they are supposed to give. For example, the kids might all line up for lunch instead of sitting in their desks when the reading time bell sounds.

Because of this, stimulus discrimination is also important. This involves the ability to distinguish between two similar stimuli.

The school kids in our example might experience stimulus generalization at first, but as they become more familiar with their school schedule and the unique sound of each bell, they will eventually learn to discriminate between the two bells.

Researchers have found that stimulus generalization can also affect whether or not we trust others. If we learn to trust someone, we might trust people who resemble trustworthy individuals.

Stimulus Generalization vs. Stimulus Discrimination

Stimulus generalization and stimulus discrimination describe ways organisms respond to similar stimuli but differ in important ways. Generalization involves a broadening of the response so that the organisms respond to similar stimuli. Discrimination involves narrowing the response so that an organism can differentiate between two similar stimuli.

Key Points to Remember

Stimulus generalization can impact the learning process in both classical and operant conditioning. Sometimes this generalization can be a good thing. In school, kids may learn skills in one setting that can be transferred into similar situations.

In other cases, it can lead to confusion and complication if there is a need to distinguish between similar stimuli.

Fortunately, people can learn how to tell the differences between similar stimuli and avoid stimulus generalization if necessary.

Sources:

Cuvo, A.J. On stimulus generalization and stimulus classes. Journal of Behavioral Education, 12, 77–83 (2003). https://doi.org/10.1023/A:1022374406394

FeldmanHall, O., Dunsmoor, J. E., Tompary, A., Hunter, L. E., Todorov, A., & Phelps, E. A. (2018). Stimulus generalization as a mechanism for learning to trust. Proceedings of the National Academy of Sciences, 115(7). https://doi.org/10.1073/pnas.1715227115

Eilifsen, C., & Arntzen, E. (2021). Mediated generalization and stimulus equivalence. Perspectives on Behavior Science, 44(1), 1–27. https://doi.org/10.1007/s40614-021-00281-3

Sigurðardóttir, Z. G., Mackay, H. A., & Green, G. (2012). Stimulus equivalence, generalization, and contextual stimulus control in verbal classes. The Analysis of Verbal Behavior, 28(1), 3–29. https://doi.org/10.1007/BF03393105