Stimulus Generalization: Definition & Examples

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  • 0:00 What Is Stimulus…
  • 0:35 Real World Examples
  • 2:58 Why Is Stimulus…
  • 3:30 Lesson Summary
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Lesson Transcript
Chris Clause
Expert Contributor
Michael Lee

Michael obtained his PhD from the University of Manitoba in Psychology. He has been teaching for the psychology department at the University of Winnipeg for the last 20 years.

In this lesson, you will learn to define stimulus generalization and apply it to real-world situations. Following this lesson, you will have the opportunity to test your knowledge with a short quiz.

What is Stimulus Generalization?

Why aren't people who are afraid of snakes only afraid of one kind of snake? Why don't children who are potty training have to re-learn the process of using the toilet every time they encounter a new one?

The answer: stimulus generalization.

In technical terms, stimulus generalization occurs when a previously unassociated or new stimulus that has similar characteristics to the previously associated stimulus elicits a response that is the same or similar to the previously associated response. In short, similar stimuli trigger similar responses when stimulus generalization is at work.

Real World Examples

Let's take a look at a couple of examples that will help you to apply this technical definition to the real world.

Stimulus Generalization and Classical Conditioning

Fear is one of the most common classically conditioned responses experienced by humans. We will use the fear of snakes to illustrate how stimulus generalization works in classical conditioning.

Imagine that a four-year-old child who is watching Nature on PBS sees a 20-foot-long green tree python devour a cute little brown mouse. While this experience is perfectly natural in the jungles of South America, the child (who has a pet mouse) immediately imagines a snake coming into her bedroom and doing the same thing to her mouse! The thought of such a thing elicits a strong fear response, including increased heart rate, pupil dilation, and anxiety, which quickly becomes associated with the snake.

So, what happens when the child goes outside to play and sees a harmless 18-inch-long brown snake in her backyard? The conditioned fear response kicks in, and even though it is not a 20-foot-long green tree python, the reaction is quite similar. This is stimulus generalization.

The person who is afraid of snakes did not have to experience a snake of every size, shape, and color in the world. Associating the key characteristics of the snake, like long and skinny, slithery, rapid tongue protrusions from the mouth, and two eyes on the sides of the head, with the fear response is enough to learn that anything that possesses those characteristics is likely a snake.

Stimulus Generalization and Operant Conditioning

Potty training is a good example of stimulus generalization in operant conditioning. When a child is learning to use the toilet, rewards are often used to increase the desired behaviors. Usually it starts off with rewarding behavior that involves becoming comfortable around the toilet, followed by rewards for sitting on the toilet, culminating in rewards for using the toilet. Typically, this experience will take place using the same toilet in the child's home.

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Stimulus Generalization

One of psychology's most infamous studies was carried out by John B. Watson and his colleague Rosalie Rayner (Watson and Rayner, 1920). It is likely that even most people without much familiarity with psychology will have heard something about the "Little Albert" experiment. Watson wanted to show that all human behaviour can be learned, even emotions. If an emotion such as fear could be learned, it would go far in advancing the view that behaviour is learned via environmental experiences.

Watson and Rayner selected an infant named Albert B. At approximately 9 months of age, Albert was tested and was judged to show no fear when successively observing a number of live animals (e.g., a rat, a rabbit, a dog, a monkey), and various inanimate objects (e.g., cotton, human masks, and a burning newspaper). He was, however, judged to show fear whenever a long steel bar was unexpectedly struck with a claw hammer just behind his back. Two months after testing Albert's unconditioned reactions to various stimuli, Watson and Rayner attempted to condition him to fear a white rat. This was done by presenting a white rat to Albert, followed by a loud clanging sound (of the hammer and steel bar) whenever Albert touched the animal. After several pairings of the rat and noise, Albert reacted with crying and avoidance when the rat was presented without the loud noise. Albert seemed to show a fear response to the rat, the rabbit, the dog, and the sealskin coat. Five days later, Albert was presented again with the rat, but also a set of familiar wooden blocks, a rabbit, a short-haired dog, a sealskin coat, a package of white cotton, and a bearded Santa Claus mask.


  • What type of conditioning, classical or operant, was used by Watson and Rayner with Little Albert? If so, explain how.
  • Were Watson and Rayner also able to demonstrate stimulus generalization in Albert? If so, explain how.

Possible Answers:

Little Albert was classically conditioned to fear the white rat. Watson and Rayner conditioned this fear by pairing the loud noise with the rat, so that eventually the rat became a conditioned stimulus for fear. By presenting stimuli similar to the rat (the rabbit, dog, etc.) to Albert, and observing the response, Watson and Rayner were also able to illustrate the generalized fear that Albert had learned.

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