Discrimination Therapy in ABA Training: Explained

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Discrimination therapy in ABA training is based on how autism therapy uses various operants, or skills, of language. Language is critically important in the identification, diagnosis, and treatment of autism. As the North American Journal of Medical Sciences explains, a failure to develop language is usually one of the first signs that a child might be on the autism spectrum. 

ABA therapy works by observing information on a client’s communication and language skills, and devising a treatment plan to identify specific forms of deficits.

Communication skills don’t just refer to spoken language skills. These skills cover any way a person with autism can communicate with others. This can include using pictures to show desires, pointing, touching, or singing. 

Verbal Operants

The Analysis of Verbal Behavior journal describes verbal operants as basic language and communication skills that children can be taught to use in any setting. These operants can be made as general or as specific as necessary, depending on a client’s level of autism severity. 

Main categories of verbal operants include mand, tact, echoic, autoclitic, imitation, and intraverbal. 

The idea behind this therapy is to teach children with autism to think beyond words as simply labels. Instead, children can learn to connect a word with a specific purpose. The goal is to help them understand how to use words in communicating ideas and expressing themselves to make clear requests, rather than just thinking of words as labels for things.

  • Mand operant: The mand operant is a demand or request. With this operant, the client will understand how to communicate what they want or need, such as learning how to ask for a toy they want.
  • Tact operant: This operant teaches a person with autism how to label a stimulus in their environment. For example, a person smells cookies baking and identifies the smell appropriately, or a child may see a ball and say, “Look, a ball!” 

  • Echoic operant: The echoic operant involves the speaker repeating what they heard. For example, the therapist says “water,” and the client repeats “water.” 

  • Autoclitic operant: This operant is dependent on verbal behavior and essentially involves the speaker giving commentary on the information given. Autoclitic operants often involve phrases like  “I think.” For example, “I think it’s going to rain today.”

  • Imitation operant: The client mimics the words or motions of the therapist or teacher. For example, the therapist claps their hands, instructing the client to do the same, and the client also claps their hands.
  • Intraverbal operant: This operant involves giving an appropriate response to something someone else said. For example, a parent may ask, “What did you do at school today?” And the child responds, “I played hide and seek with Amy.”   

Antecedents are the circumstances that happen directly before, leading to the action. All operants have antecedents, and the consequence is the behavior that follows.  

Operants are designed with a motivational operation antecedent, an environmental antecedent, or a verbal behavior antecedent. The consequence of each operant either directly comes from the motivational operation or from one that is educational or social.

Receptive Language

The other component of verbal behavioral therapy that leads to discrimination therapy is receptive language. The Behavior Analysis in Practice journal explains that receptive language is the practice of “responding appropriately to another person’s spoken language.” 

Simply put, this covers whether the client is able to follow direct instructions. If a therapist asks the client to hand them a cup, will the client know that the word “cup” refers to the object we use to drink liquids? 

Such fundamental building blocks of language development will form naturally in the brains of neurotypical children. For children on the autism spectrum, this formation does not occur, or it occurs at a very stunted rate. In either case, these children, and sometimes adults, require a great deal of intensive assistance for this development to happen. Discrimination training is a vital part of that assistance. 

Discriminative Stimulus & the Stimulus Delta

Discrimination therapy is intended to help clients move beyond simply guessing how the therapist wants them to respond and instead help clients to actually pay attention to the object or instruction. 

For instance, a client might understand that the request of “give me...” an object will lead to positive reinforcement, so the client associates “give me...” with a positive outcome. But if the client focuses only on the “give me...” request, instead of the actual object (a ball instead of a cup, or a doll instead of a book), then this is a failure in understanding. 

The goal of discrimination therapy is to help the client discriminate between what is said, to help them choose the correct item.


In discrimination therapy, if the client chooses the correct item to give to the therapist and receives positive reinforcement, this is known as the discriminative stimulus. The opposite of this is the S-delta (stimulus delta), wherein there is no reinforcement. 

The discriminative stimulus is the stimulus that is present when the desired behavior is reinforced. The client will learn, through reinforcement, that they have to exhibit certain behavior when the discriminative stimulus is present. 

The stimulus delta, on the other hand, is a stimulus in the presence of which a particular response from the client will not be reinforced. In other words, the client will be denied their desired reinforcement if they respond inappropriately. 

People on the autism spectrum are naturally inclined to respond in the presence of stimuli that are similar to the discriminative stimulus. In discrimination therapy, these similar stimuli are the stimulus delta. With no positive reinforcement, the goal of discrimination therapy is to eventually reduce the response to the stimulus delta to negligible levels. 

The question of discrimination therapy is to determine how well the client understands the difference between the discriminative stimulus and the S-delta. For example, if the prompt is “give me the cup,” can the client choose the cup (the discriminative stimulus) and not the spoon (the stimulus delta) when both objects are on the table? In other words, can the client discriminate between two objects when simultaneously presented with both?

The idea behind discrimination training is to teach clients a skill that can be applied across any kind of target and in any kind of environment. A client who learns to discriminate can then discriminate between objects, pictures, receptive labels, and other things. 

How Does Discrimination Therapy Work?

Discrimination therapy in ABA is considered a beginner program. There has to be a paired relationship between the therapist and the client, which allows there to be instructional control. 

In order for discrimination therapy to be used, other skills must be developed, such as joint attention (which Biological Psychiatry explains is when the therapist and the client have an interest in the same object), whether the client can follow a point (if the therapist points at an object, the client will look at it), and whether the client can follow simple, one-step directions. 

Discrimination therapy starts with just one item. A registered behavior technician will begin with an object that has some meaning to the client; different clients will prefer different objects. In order to ensure that the client responds to the therapy properly, it is best if a neutral item that has some meaning is selected. Picking an object with too much meaning, something the client really wants, might be too distracting for them. 

Some people on the autism spectrum don’t have fully developed picture-to-object correspondence, so using flashcards may not be effective. For this reason, most RBTs will prefer to use real items. 

Discrimination Therapy in Action

The therapy will start with the registered behavior technician holding out their hand and telling the client, “Give me [the item],” or even just saying the name of the item. Having too many words in the request may be difficult for the client to process. 

In the first stage of the therapy, there will be only one item on the table: the item that the RBT has asked for. 

In the second stage, there will be two items out. Ideally, the two items will be very different, to minimize any chance of the client confusing one for the other. 

In the third stage, there will be three items out: the desired object, plus two non-preferred items.

Each time the client gives the correct item to the therapist, this is celebrated with reinforcing behavior. If the client gets it wrong, the therapist might use mildly negative reinforcement to guide the client toward making the right choice. 

The goal of discrimination therapy is to get the client to between 80% and 100% mastery for an item, at which point the therapist will repeat the process with a new item. 

In tougher trials (for clients with milder presentations of autism or clients who have demonstrated sufficient mastery), there might be only one discriminative stimulus and up to four stimulus delta. 

Discrimination Therapy Is Used to Build Impulse Control

Discrimination therapy is found in all walks of life. As long ago as 1988, the Journal of Abnormal Child Psychology explained how discrimination therapy was used as a form of impulse control. To this day, it still is used in this manner. 

Most neurotypical people develop a natural sense of learning how to choose the discriminative stimulus over the stimulus delta in order to achieve a desired response. However, people with some developmental or behavioral disorders may not be able to do this without therapeutic help. 

Often, people on the autism spectrum do not have the language and contextual tools to understand how another person’s reinforcement connects with carrying out appropriate behavior. Discrimination therapy introduces people with autism to the connection between making acceptable choices (by discriminating between the discriminative stimulus and the S-delta), receiving reinforcement, and then applying that learning to other situations.

Like other approaches used in ABA therapy, discrimatination therapy takes time. Clients often work with therapists for many hours per week, and it can take weeks and even months to see results from this work. However, the results can be substantial when they do take hold. 

As with ABA therapy in general, the earlier this therapeutic approach is introduced in life, the better the long-term outcomes.