What Is Stimulus Generalization in Psychology?

In the conditioning process, stimulus generalization is the tendency for the conditioned stimulus to evoke similar responses after the response has been conditioned. For example, if a dog has been conditioned to bark with excitement when it hears the jingle of keys in the front door, similar sounds may evoke the same response.

Examples of Stimulus Generalization

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

The Little Albert Experiment

One famous psychology experiment perfectly illustrated how stimulus generalization works. In the classic Little Albert experiment, researchers John B. Watson and Rosalie Rayner conditioned a little boy to fear a white rat.

The researchers observed that the boy experienced stimulus generalization by showing fear in response to similar stimuli, including a dog, a rabbit, a fur coat, a white Santa Claus beard, and even Watson's own hair.

Instead of distinguishing between the fear object and similar stimuli, the little boy became fearful of objects that were similar in appearance to the white rat. (Though it should be noted, this experiment has been the subject of much debate and controversy in recent years).

Other Examples of Stimulus Generalization

Other real-life examples of stimulus generalization include:

• A mother is used to responding when she hears her child ask for help, but may also respond when she hears another child say "Mom."
• If you developed a phobia after being bitten by a dog, you might experience a similar fear response when you see other types of dogs.
• Students recognize that a bell signals the end of class; if a similar sound occurs, they may think that class is over.
• If you have a bad experience at the company Christmas party, you might generalize your feelings to similar social events.
• If you associate a certain type of food with feelings of pleasure, you might be more willing to try similar foods because you generalize those feelings to products that are similar in appearance or packaging.
  

Why Stimulus Generation Is Important

It is important to understand how stimulus generalization can influence responses to the conditioned stimulus. Once a person or animal has been trained to respond to a stimulus, very similar stimuli may produce the same response as well.

For example, if you are using conditioning to train your dog to sit, you might utilize a treat to build an association between hearing the word "Sit" and receiving a treat. Stimulus generalization might cause your dog to respond by sitting when she hears similar commands, which may make the training process more difficult.

In this case, you would want to use stimulus discrimination to train your dog to distinguish between different voice commands.

Stimulus generalization can also explain why the fear of a certain object often affects many similar objects.

A person afraid of spiders generally won't be afraid of just one type of spider. Instead, this fear will apply to all types and sizes of spiders. The individual might even be afraid of toy spiders and pictures of spiders. This fear may even generalize to other creatures that are similar to spiders, such as other bugs and insects. 

Stimulus Generalization in Classical and Operant Conditioning

Stimulus generalization can occur in both classical conditioning and operant conditioning. Little Albert's fear of white furry objects is a great example of how stimulus generalization works in classical conditioning. While the child had originally been conditioned to fear a white rat, his fear also generalized to similar objects.

In operant conditioning, stimulus generalization explains how we can learn something in one situation and apply it to other similar situations.

Stimulus Generalization vs. Stimulus Discrimination

However, a subject can be taught to discriminate between similar stimuli and only to respond to a specific stimulus. For example, imagine that a dog has been trained to run to his owner when he hears a whistle. After the dog has been conditioned, he might respond to a variety of sounds that are similar to the whistle.

Because the trainer wants the dog to respond only to the specific sound of the whistle, the trainer can work with the animal to teach him to discriminate between different sounds. Eventually, the dog will respond only to the whistle and not to other tones.

A Classic Experiment on Generalization and Discrimination

In another classic experiment conducted in 1921, researcher Shenger-Krestovnika paired the taste of meat (which is the unconditioned stimulus in this instance) with the sight of a circle. The dogs then learned to salivate (which is the conditioned response) whenever they saw the circle.

Researchers also observed that the dogs would begin to salivate when presented with an ellipse, which was similar but slightly different than the circle shape. After failing to pair the sight of the ellipse with the taste of meat, the dogs were able to discriminate eventually between the circle and ellipse.

Takeaways

Stimulus generalization can play an important role in the conditioning process. Sometimes it can lead to desirable responses, such as how learning good behaviors in one setting can transfer to displaying the same good behaviors in other settings.

In other cases, this tendency to generalize between similar stimuli can lead to problems. Failing to distinguish between two commands might make the learning process more difficult and can lead to incorrect responses.

Fortunately, the same conditioning principles that are used to teach new behaviors can also be applied to help learners discriminate between similar stimuli and only respond to the desired stimulus.