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Stimulus Discrimination Psychology Definition & Examples

What is stimulus discrimination?

A discriminative stimulus is a stimulus that when it is present, generates a particular response and the response is usually faster, more frequent, and more resistant to extinction. The responding behavior is then subjected to discriminative stimulus control. A discriminative stimulus (Sd or SD) is created when the response is reinforced in its presence, but not when it is absent​1​.

For example, a child requests to watch TV, and historically, he is granted more screen time when his Mom has to get on a conference call for work, but never when she doesn’t have to take a call. So having a work-related phone call is an Sd that controls the child’s requesting behavior.

child uses screens while mother is busy in meeting

Discrimination and Classical Conditioning

When an originally neutral stimulus is repeatedly paired with an unconditioned stimulus to generate a response, the neural stimulus becomes a conditioned stimulus for that response.

Discrimination and Operant Conditioning

Discriminative stimuli have control over a particular behavior because the behavior is reliably reinforced through positive or negative reinforcement and punishment when the stimuli are present and not when they are absent.

Stimulus Discrimination Examples

Here are some discriminative stimulus examples.

  • When a child asks for candy, she always gets one during grandma’s visit, but not in her absence. Grandma’s visiting is an Sd that controls the child’s asking behavior.
  • When the traffic light turns green, drivers keep their car going forward, but not when the light turns red. The green light is then an Sd for going while the red light is for stopping.
  • When a manager is present, the employees work faster than when she’s not present. The manager’s presence is an Sd that controls how fast the employees do their work.
  • When Mom is present, the child completes his homework, but when Mom leaves the room, the child stops doing homework. Mom’s presence is an Sd that controls the homework-doing behavior.
  • You give a dog a treat when it barks at a certain person, but not when it barks at another person. Then that first person becomes an Sd that controls the dog’s barking behavior.

Stimulus Discrimination vs Generalization

Stimulus generalization is defined as the extension of conditioning so that similar stimuli that have not been reinforced can act as a conditioned stimulus to generate a specific response​2​. Now an individual responds to not only the one stimulus that has been reinforced but also others that share similar characteristics. Generalization can occur in classical conditioning as well as operant conditioning.

For example, the bee stings you. You will begin to fear it resulting in fear conditioning. But you will also begin to fear other insects that look similar. The more similar another insect is to a bee, the more you will fear it.

Your conditioned response (fear) has generalized from the training stimulus (bees) to another stimulus (insects similar to a bee).

Discriminative Stimulus in Parenting

Discriminating stimuli are often used in parenting to help children with Autism Spectrum Disorder (ASD) and those with mental retardation​2​.

A branch of non-mainstream psychology, called Applied Behavior Analysis (ABA), has emerged to teach Sd-based techniques to parents who have kids with ASD. These ABA techniques help children develop social skills and decrease behaviors that may interfere with their independence in life​3​.

In ABA therapy, discriminative stimulus and differential reinforcement are used to teach children how to respond appropriately or give a correct answer. An ABA therapist will work with parents to make sure that they understand how to apply the correct techniques.


  1. 1.
    Michael J. The Discriminative Stimulus or SD. BEHAV ANALYST. Published online April 1980:47-49. doi:10.1007/bf03392378
  2. 2.
    Foxx RM. Applied Behavior Analysis Treatment of Autism: The State of the Art. Child and Adolescent Psychiatric Clinics of North America. Published online October 2008:821-834. doi:10.1016/j.chc.2008.06.007
  3. 3.
    Alberto P, Troutman AC. Applied Behavior Analysis for Teachers. Pearson Merrill Prentice Hall; 2006.


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