Discriminative Stimulus in ABA Therapy: Explained
A discriminative stimulus is the technical term in behavioral psychology for something, like a person or an event, that precedes a behavioral response.
It is the opposite of a stimulus generalization, in which the person learns that one behavior (like asking for candy in a grocery store) can also be performed in other places with candy (like a convenience store). Instead, a discriminative stimulus is a behavior specifically associated with or triggered by that stimulus.
The concept comes from operant conditioning, a form of changing behaviors that became one of the core concepts in applied behavior analysis (ABA) therapy. ABA therapists may use an approach called the ABCs to learn the antecedent (or discriminative) stimulus, an autistic client’s behavioral response, and the consequences. They will then either find a new antecedent or reward a different behavioral response to a previous discriminative stimulus.
How Does a Discriminative Stimulus Work?
Operant conditioning is a psychological approach to changing behaviors through training by using rewards. In the original model that used animals, punishments were also used to change behavior.
The discriminative stimulus describes something that is the trigger for a specific behavior. The discriminative stimulus comes first; then, the behavior follows as a direct result of this stimulus. The conditioned stimulus produces the response, while the discriminative stimulus signals the opportunity to respond.
The discriminative stimulus sets up the occasion for a specific behavior to occur because the resulting behavior has been reinforced in the past. The stimuli are discriminatory because they are specific and elicit a specific response.
What Is Operant Conditioning?
Operant conditioning was developed in the 1950s by B.F. Skinner, using a device called a Skinner Box. Animals like lab rats or pigeons were placed in the box and directed to perform certain behaviors with a series of rewards and punishments.
For example, some pigeons were taught to peck keys when they lit up red by receiving a reward of food. They were dissuaded from pecking keys that were green by receiving a small electric shock. The discriminative stimulus in this instance is the color of the key. If it is green, the pigeon knows that pecking the key will be reinforced in a positive way, and if the key is red, pecking will result in something uncomfortable. As a result, the pigeon will learn to peck green keys and avoid pecking red ones.
Although displays of operant conditioning were part of Skinner’s research, his approach highlights that this is part of the human learning process. When children learn to speak, they are conditioned to learn that certain words apply to certain items.
For example, when a child learns to apply “Dada” to the first male presence in their lives (their father), they may start using the word on other men they meet. This is indiscriminate stimulus, and parents will guide their child to use the word only with the father, making his presence a discriminate stimulus for the word “Dada.”
Adults working through a weight loss program may receive a token as both a reward for losing a certain amount of weight and as a discriminatory stimulus to continue losing weight, increasing motivation to continue the program.
In applied behavior analysis (ABA), operant conditioning uses discriminative stimuli to help people with autism understand when certain adaptive social behaviors are expected, so they can respond appropriately. The discriminative stimulus in ABA therapy is called the antecedent.
Using a Discriminative Stimulus in ABA Therapy: The ABC Chart
The antecedent or discriminative stimulus is part of a specific process in ABA therapy called the ABCs. This is an acronym for:
A. Antecedent: These are the circumstances, actions, or events that
occur before a certain behavior.Consequence: This is the action or
response after the client’s behavior.
B. Behavior: This is the client’s response.
C. Consequence: This is the action or response after the client’s
Using the ABCs is a way for ABA therapists to understand when their clients respond in certain ways. This is an ABC Chart. It may list examples like:
A. An ABA therapist asks their autistic client to clean up a puzzle.
B. The child yells “No!”
C. The ABA therapist distracts the child with another activity.
Here is another example:
A. The teacher stands by the chalkboard at the start of class.
B. Students become quiet and pay attention to the teacher.
C. There is a reward to students who become quiet.
Keeping track of this information can help therapists, parents, teachers, and other adults in the child’s life understand how antecedents and consequences impact the child’s decisions and behaviors. The child will learn to associate certain discriminative stimuli, or antecedents, with certain consequences.
An Example of a Discriminative Stimulus Applied During ABA Therapy
ABA therapy uses operant conditioning to reward good behavior and to occasionally reprimand bad behavior.
As ABA therapy became one of the more popular approaches to treating autism, programs were criticized for how they punished clients, especially children. Modern ABA therapy does not punish, but instead simply fails to reward maladaptive responses to antecedents and uses rewards to enhance positive behavioral change. Children with autism respond well to operant conditioning used in this way, as repeated sessions encourage adaptive behaviors.
A case study offers a good example of how a discriminative stimulus might be used during ABA therapy. A child with autism had a stereotypic behavior (a repetitive behavior that is reinforced in the individual’s brain but is maladaptive to communication or socialization) and was taught to manage their stereotypy using a green card and a red card as antecedents. The child’s stereotypic behavior involved shaping objects, most often string, in front of their face.
When the green card was on the child’s desk, they were free to engage in this self-stimulating behavior. When the red card was on their desk, they had to stop and pay attention to their therapist.
At first, if the stereotypic behavior occurred when the red card was out, the child would be verbally or physically redirected to do something else. For example, they would be told to stop, or the string would be taken away from them. Then, their attention was focused on a different project. The green card could then be placed down as a reward for avoiding the stereotypic behavior.
ABA Uses Many Concepts of Behavior Therapy to Help Autistic Children
It is important to avoid harsh punishments while using ABCs during ABA therapy, as children with autism may have different behavioral responses to a sharp tone of voice, removing a favored object, or something else intended to redirect their attention. Instead, failing to reward a maladaptive behavioral response to a discriminative stimulus, while rewarding positive change, makes that a conditioned stimulus. The child then learns that their behavior can elicit a consequence that is in their favor.
There are other concepts with operant conditioning and other behavioral therapy techniques used in ABA therapy. If your child does not respond to changes in consequences for their behaviors or new discriminative stimuli, their ABA therapist can find other ways to encourage learning and skill-building.
- The Scientific Concepts Behind Applied Behavior Analysis. (October 2018). Insight Magazine.
- Behavioral Principles: Stimulus Discrimination and Generalization. (November 2017). Psychology Department, St. Cloud State University.
- Three Types of Learning and Their Relevance to ABA Parent Training. (November 2019). Psych Central.
- ABC’s of Behavior (Antecedent – Behavior – Consequence). (July 2017). PsychCentral.
- Developing Stimulus Control for Occurrences of Stereotypy Exhibited by a Child With Autism. International Journal of Behavioral Consultation and Therapy.