The Discrete Trial

Introduction to Discrete Trial Training (DTT)

Applying ABA to the treatment of Autism using the CARD program has two primary components: Skill Repertoire Building, where the antecedents and consequences are manipulated to teach new skills and Behavior Management, where the antecedents and consequences are manipulated to reduce inappropriate behavior. Skill Repertoire Building is the greatest component of the CARD program.

What is Discrete Trial Training?

Discrete Trial Training (DTT), is one of the teaching techniques used in Applied Behavior Analysis (ABA). ABA is the application of the Principles of Behavior to socially important areas. ABA and DTT are not the same thing. DTT is only one of many teaching methods used in ABA.

A discrete trial is made up of three components: The Antecedent, a Response and a Consequence. It is then followed by another trial.

There are several aspects of the antecedent to consider:

  • The Establishing Operation or EO:
  • Discriminative Stimulus or SD: In a DTT the SD would be the teacher saying, “touch the car”, or a gesture that the child needs to interpret. The response is that the child touches the car. The consequence is that the child is rewarded (e.g.. a cookie). These three components parallel the 3-term contingency (ABC’s). The SD is the antecedent, the response is the behavior, and the consequence remains the consequence. The SD is not always verbal because in the natural environment communication is not always spoken.

Why use Discrete Trial Training?

Discrete trial training is used in ABA because Autistic children typically do not learn by watching others. (Consider this article on mirror neurons and autism). Because of this it is important that children receive as many opportunities for learning as possible. This makes discrete trial training well suited for teaching, because a high number of discrete trials can be presented within a therapy session, even per minute, or hour, or day. The more trials presented the more opportunities a child has to learn. Moreover, DTT allows the child know that they are expected to respond. Because the sequence is always the same (i.e., Sd, Response, Consequence) the child learns that when an Sd is presented a response is expected.

Typically before treatment children with autism often do not respond to teachers, other adults or peers. Or, they may begin to engage in behaviors that may surprise or even scare adults when given instructions. For example, a relative might ask a child to close a door upon entering the house, the child might then, begin to hit themselves in the head, this might frighten the relative and cause them not to persist in their instructions. Over time then, the child learns that hitting themselves in the head is a way to avoid having to comply with instructions. Using DTT, a child is always expected to respond, either on their own or with help. DTT also lets the child know if their responses are correct, this is because a consequence is given immediately after a response.

Additionally, DTT assists in helping the therapist maintain consistency. Consistency is critical when working with children who have autism and maintaining consistent consequences is imperative in order to increase desired behaviors and to decrease problem behaviors. In discrete trial training a consequence always follows every response which helps ensure that the consequences are applied consistently.

Finally, DTT allows therapists to easily take data and track progress.

The Antecedent

Discriminative Stimulus (SD)

What are stimuli?

Stimuli are anything that can be seen, heard, smelled, tasted or felt.

What is Sd? w/examples

When working with children with autism it is important to establish various stimuli as discriminatory stimuli or Sds. The definition of SD is: A Stimulus, in the presence of which a particular response will be reinforced, and in the absence of which that response will not be reinforced. In practice, a stimulus is an SD is a stimulus in which a child reliably responds and does not respond in the absence of that stimulus. This occurs when the child’s response in the presence of that stimulus has been reinforced in the past. Most Sds presented will be verbal or visual or a combination of verbal and visual.

What is the difference between Visual and Verbal Sds?

A Verbal stimuli is generally something said to a child. Once a stimuli is established as an SD it will reliably evoke a particular response. For example, a therapist may ask, “what does a dog say?”, if this question has been established as a verbal SD, it will evoke the response, “woof”. Alternately, a therapist may say, “tell me something that is red”, to which a child might say, “fire truck”, “stop sign” or any other thing that is red. A parent often uses SDs with their child. A Dad may ask the question, “what did you do at school today”, which evokes a response from the child about what they did at school today.

A Visual stimuli is anything that someone sees. Neurotypical children naturally label objects, actions and activities they see going on around them. We present visual Sds because we want autistic children to do the same. A photo could be a visual SD. When establishing a photo as a visual SD we want the photograph alone to evoke a response from the child.

Using a combination of visual and verbal SDs simply means combining the two types of stimuli and presenting them in combination to the child. Such as saying, “what is it?” when presenting a photograph or an object.

The therapist will not select the SDs but rather this will be designed by the BCBA.

Guidelines for Presenting SDs

  1. Have the child’s attention before presenting the SD: Assure that the child is either looking at you or attending to the task at hand prior to presenting the SD. If the child is engaged in another activity or distracted by something and you fail to gain the child’s attention before presenting the SD the child will be unlikely to respond.
  2. Avoid presenting the child’s name with the SD: This is important because the child’s name could become and extraneous variable that the child learns to ignore, then when you attempt to use the child’s name to gain their attention the child may not respond. Additionally, the child may start to respond only when their name is said at the start of the SD. When speaking with typical children one on one, it is not necessary to call their names to get them to answer. With autistic children we do this because it is more difficult to get their attention. If you call the child’s name before the presentation of each SD, you are compensating for their poor attention rather than teaching the child to attend to the SD. It is okay to infrequently use the child’s name with the SD, but if you find yourself doing this often, it usually means the child is not making eye contact with you and you are compensating by calling the child’s name.
  3. Avoid repeating SDs without giving consequences: Consistency is crucial when applying consequences. Repeating SDs without giving consequences may result in high rates of non response. We want the child to learn that every time we present an SD a response is expected. For example, if we repeat the SD “Come Here” and the child fails to come each time, and there is no consequence the child will not learn that a response is expected to the SD, moreover the child will learn that there are no consequences for nonresponse.  Each SD must have a consequence.
  4. Change the target SD only when instructed to do so by the BCBA: The target SD will be identified for each skill building lesson by the BCBA and noted in the child’s log book, the place the child’s lessons and data are stored. It is important that each therapist uses the same target SD. For example, the child cannot expressively label anything yet, and the therapist has been instructed by the BCBA to teach the child to expressively label 3-d objects using the target SD “What is this?” and then showing the child an object, like a shoe. One therapist decides to use a picture of a shoe, while everyone else uses a real shoe. If all therapists do not use the same stimulus for the target response, it can confuse the child and slow the child’s progress. However, if everyone uses the same SD than the child has a greater chance for success. After the child has acquired the expressive response, “shoe” to the real shoe, the BCBA may instruct to begin varying the shoe presented, mixing different real shoes with pictures of shoes, doll shoes and other representations of shoes.
  5. Initially, SDs should be clear and concise: Starting with simple terms makes it easier to learn, consider yourself, if you were just starting to learn how to speak English, and were learning how to say apple, which would be easier? To have someone show you an apple, and say “apple”, or to have someone show you and apple and say “Look at what I am holding. We call this an apple in the English language”. The first example was easier because there was no additional information given. When a child with autism is learning beginning level language skills, it is important to be clear and concise with your SDs. If a child is learning to respond to “come here” and the therapist says, “Can you come over here and sit down please?” it is more difficult for the child to respond correctly. After a child has learned beginning level language skills, verbal SDs and other instructions become more complex and less concise. When a child has moved on to more complex language skills, “Can you please come over here and sit down” may be an appropriate SD. The complexity of the SDs presented will be determined by the BCBA.
  6. The child should respond only after the entire SD is presented: If the child responds before the SD is completed, the child is not responding to the SD, and therefore is not learning what we are intending to teach. Consider the example where a child is being taught to respond to the SD, “Touch car”, and three objects are placed in front of her: a car, a shoe, and an apple, you begin to say your SD “Touch” but the child touches the car before you complete the SD, the child is not responding to the entire SD, instead only to the word “touch”. In fact, the child is not responding to the part of the SD which would allow them to respond correctly, that is “car”, therefore the child is not learning what you are trying to teach them. However, if the child only responds once the entire SD has been presented than the child is responding to the SD and is more likely to learn what you are trying to teach.

Consistently following these six guidelines, when presenting SDs will ensure that you are providing each child the best opportunity for success.

Establishing Operation (EO)

In some cases the antecedent in a discrete trial may include a condition or a physical state such as hunger. Consider the following example. The child is hungry, and they have no food (antecedent), the child asks for a banana (response), and the therapist gives the child a banana (consequence), in this example the antecedent is not an SD, it is an EO.

What is an EO? w/examples

An establishing operation or EO is a condition that makes an item or activity more reinforcing, and evokes responses that produce that item or activity. For example, a child is more likely to request a drink if that child hasn’t had a drink for a while rather than if the child just had a large glass of water. The BCBA may tell you to set up situations like this to make a specific item or activity more reinforcing. In other words the therapist may be asked to contrive an EO for a particular item or activity as the antecedent for a particular skill building lesson. For example, a child is learning to request preferred items, and the child loves to color pictures in coloring books, the BCBA instructs the therapist to contrive an EO for crayons, by giving the child the coloring book but withholding the crayons. The presence of the coloring book without crayons is an EO that momentarily increases the reinforcing value of crayons for the child. The child then requests the crayons, and the therapist reinforces the child’s response by giving them the crayons. In this example of a discrete trial the therapist contrived an EO for crayons as the antecedent. It’s important to note that the antecedent in a discrete trial may be an EO an SD, or both. The BCBA will specify the antecedent for each skill building in a child’s program.

The Response

What is the response in terms of a discrete trial?

A response is the specific instance of a particular behavior. An example of a response is when a therapist tells a child to “touch the car”, and the child responds by touching the car, which results in the therapist giving the child a small piece of candy. The specific instance of the child touching the car is the response.

3 Possible Categories of Responses:

Correct Response: When a child responds to a particular SD with the target response (as defined by the BCBA) The target response will be defined in clear, objective and measurable terms.

Incorrect Response: Any response that is different from the target response.

No Response: Occurs when the child does not react at all to the SD.


The child is learning to receptively identify objects. The BCBA has specified the target SD as “Touch the Car”, and the target response as the child touching any part of the car with their hand. If the child were to touch a different object in response to the SD the response would be considered incorrect. And if the child just sits there and doesn’t touch any item, than that would be no response.

Guidelines Related to the Response:

  1. The therapist must be consistent about what is considered to be a “correct response”: The BCBA will define the correct or target response in clear, objective and measurable terms for each skill building lesson in a child’s program.  As a therapist it key that the child is required to respond in a manner that is consistent with the defined target response. If inconsistent responses are allowed by the therapist, than the child will have difficulty acquiring the response specified. Example: A child is learning to request, the target response has been defined as “any full sentence request that includes a verb and a noun”. So if the child wants to go see their mother, the child should say, “Can I go see my mommy?”, or “Can I see mommy?” or “I want to see mommy”. However, if some therapists are accepting “mommy” as the correct response than the child will have difficulty acquiring the target response. Alternately, if no therapist accepts “mommy” as a correct response, and everyone requires the child to use a verb and a noun in the child’s request, than the child will learn to incorporate actions or verbs into their requests more quickly. As the child is consistently engaged to require this target response by everyone who is working and interacting with them, being consistent does not mean that there cannot be variability in the child’s responses, there are several ways to reach the target response. We want the child’s responses to vary, this is normal.
  2.  Be sure that extraneous behavior is absent: In other words a response that includes extraneous behavior should be considered incorrect. Extraneous behavior is anything that the child says or does that is not related to the target response. Example: The therapist presents the SD, “what’s your name?” to the child, the child responds “Bella” and while responding the child is flapping their hands, as a consequence the therapist gives the child a cookie for saying their name, however, the hand flapping is an extraneous behavior–so this should not be considered a correct response. In this example the therapist may have inadvertently reinforced the extraneous behavior. As a result, the child may be more likely to flap their hands in the future, when asked what their name is.  Now, using the same example let’s say that the therapist does not accept the response with extraneous behavior as correct, and instead of receiving a consequence of a cookie the child receives the consequence of an error correction procedure (as defined by the BCBA).
  3. Limit the time between the SD and the response to no more than 3 seconds: If the child takes longer than 3 seconds from the completion of the SD to the initiation of their response, than this should be considered an incorrect response. If the child is given a reward for responding after 3 seconds, than delayed response may be inadvertently reinforced.
    1. Example: A therapist is teaching a child to respond appropriately to greetings. The therapist says, “hi Toby” and after 7 or 8 seconds the child says, “hi”. The therapist rewards the child with social praise, and tickling the child gently. In this example the child is learning to respond very slowly to greetings. In natural environments, children are expected to respond very quickly to verbal SDs, if the child has learned to respond very slowly, he or she will likely miss many opportunities to interact with adults and peers in natural environments and thus experience failure in these settings. Imagine the same example but instead of allowing 7 seconds to go by the therapist treats the response as an incorrect response, and implements the error correction procedure (as defined by the BCBA). In this scenario, the reward or reinforcer is provided only for correct responses that occur within three seconds of the SD. Therefore, the child will be more likely to respond quickly to adults and peers and thus experience success in their natural environments. The length of time to respond will be determined by the BCBA for each learning skill based upon the learning goals and the individual needs of the child, as well as the complexity of the task presented.
    2. Example: A child is being taught to point and find pictures in a book, the therapist and the child are looking at a page in a book that has many images or pictures on it. The therapist says, “Find the bird”. The child begins to scan the page, looking for the bird. This task naturally requires a longer response time, the BCBA may instruct the therapist to give the child up to 20 seconds to locate the target response as long as the child is actively scanning the page. Additionally, when initially beginning work with a child longer response time may be given. Once the child is successful with this longer time frame, the goal is to systematically decrease the time given to respond. In this way, the child experiences success as they learn to respond more and more quickly.

Consistently following these guidelines will increase the likelihood that the child will acquire target responses, and experience success in his or her program.

The Consequence

What is a Consequence?

A consequence is the outcome that immediately follows the child’s response. The consequence is the most important part of a discrete trial, because the consequences that follow a behavior control whether that behavior will increase or decrease (a core principle of ABA). If a particular behavior produces “good things” or eliminates “bad things” we tend to repeat it. However, if a particular behavior produces “bad things” or eliminates “good things” we tend to stop engaging in this behavior. Without consequences, no learning would take place.

Example: The therapist presents the SD, “Give me the blue cup” . The child hands the therapist the blue cup. The therapist than gives the child a chip. The presentation of the chip is the consequence or the outcome that immediately follows the child’s response.

When teaching a child a new skill there are two possible consequences that will follow a response. The first is reinforcement, reinforcement is used following a correct response. The second possible consequence is an error correction procedure. An error correction procedure is used following no response or an incorrect response.

What is Reinforcement? What is a Reinforcer?

Reinforcement is the procedure of providing consequences for behavior that increase or maintain the strength of that behavior. Reinforcement is the key to teaching new skills. So practically speaking, reinforcement is the immediate presentation of a preferred stimulus or the immediate termination of an aversive stimulus following a response, which results in an increased frequency of that response in similar situations. The stimulus that is presented or terminated is called the reinforcer or stimulus reinforcer which is abbreviated SR.


The child is learning to go to various rooms in their home when instructed. The therapist says, “Go to the kitchen”. The child walks to the kitchen and is immediately given a chip (the child’s favorite food). Over time, the child goes to the kitchen more and more frequently for this instruction. This is reinforcement, because the result was an increased frequency of the response over time. The stimulus reinforcer presented in this example, ‘the chip’  is called the reinforcer.


The child’s sibling is listening to music and the volume is very loud. Loud music is aversive to the child. The child asks their sibling to turn the volume down. The sibling immediately turns the volume down which eliminates the aversive aspect of the music… it’s volume. Over time, the child will ask their sibling to turn down the volume more frequently in the presence of loud music. This is an example of reinforcement because the result was an increased frequency of requests to turn the volume down over time. The reinforcer in this example is the absence of loud music.

It is important to note that if the response does not increase in frequency, than the stimulus being presented or terminated is not a reinforcer and reinforcement has not taken place.

Categories of a  Reinforcer:

Primary or Unlearned Reinforcers:

These are also known as Unconditioned Reinforcers. These are things that reinforce our behavior from birth. Such as food and drink. These are typically the most powerful reinforcers.

Secondary or Learned Reinforcers:

These are also known as Conditioned Reinforcers. This is a behavioral term that essentially means ‘learned’. These are things that become reinforcers because they have been paired with  already effective reinforcers and may include such things as praise, rough housing, playing with toys, earning money, or taking a break. These are things that may function as reinforcers for a child due to a history of being paired other things that are already functioning as reinforcers for that child.

Typically, both categories of reinforcers are used to teach a child new skills. There are several factors which influence the effectiveness of a particular reinforcer. That is, how effectively or quickly it will result in an increase of the frequency of the response that it follows. One of these factors relates to conditions that effect a child’s motivation. In other words, food will likely function as a reinforcer if the child is hungry and has not eaten for a couple of hours. However, if the child has just eaten a large meal than food will probably not function as an effective reinforcer. The condition of hunger is called an establishing operation.

What is an Establishing Operation (EO) as it Relates to the Reinforcer?

There term EO or establishing operation is a condition that makes an item or activity more reinforcing, and evokes responses that produce that item or activity. Practically speaking an EO is an antecedent condition that increases motivation for a particular object or event, and generates behavior that has previously produced that object or event.


A child has not eaten for several hours, which increases her desire for food, that is this condition momentarily increases the strength of food as a reinforcer for this child. At the same time, this condition or EO also evokes responses that have produced food in the past, such as a request for pretzels, or opening the pantry door and getting pretzels. Now, after the child has eaten several pretzels, she may grow tired of pretzels and become thirsty. That is, the EO has now changed. The current conditions of food satiation momentarily decreases the pretzels as a reinforcer and momentarily increases the strength of water as a reinforcer as the child is now thirsty.

So for a reinforcer to be effective, the child must be deprived of that item or activity at some level.

Guidelines for Delivering Reinforcers:

  1. Limit free access to potential reinforcers, and instead deliver reinforcers contingent upon target behavior: If a child has free access to his or her reinforcers throughout the day the reinforcers will lose some of their reinforcing power resulting in ineffective intervention. Example: Playing on the computer is a child’s favorite things to do and the child  is allowed to play on the computer whenever they want. By the time the therapist arrives to work with the child she has already spent a significant amount of time playing on the computer and is no longer interested in this activity. The EO for computer playing is no longer in effect. If the therapist attempts to use computer playing time as a consequence for engaging in a particular target skill the therapist will likely discover that playing on the computer is no longer functioning as an effective reinforcer, the child does’t want to play on the computer any more. This child like many children with autism may have a limited number of potential reinforcers, thus the therapist may have a very difficult time finding effective reinforcers to use rendering her therapy session ineffective. 
  2. Conduct preference assessment frequently: Preference assessments are procedures that are used to systematically identify preferred stimuli that may function as reinforcers for a specific individual. This is done because EO’s influence the reinforcing effectiveness of particular items or events and the EO changes over time. Thus the child’s preferences and thus their reinforcers will change throughout a given session. If frequent preference assessments are not conducted, effective reinforces will not be presented thereby reducing or eliminating the effectiveness of the learning session.
  3. Deliver the reinforcer after one-half second of the target response: Research in the field of behavior analysis shows that delays in the presentation of the reinforcer, even by just a few seconds can result in minimal or no learning. When a reinforcer is presented with delay it is unlikely to effectively function as a reinforcer for a correct response and the child may fail to acquire the new skill.
  4. The reinforcers used should be easy to give and easy to remove: Any reinforcer used should be easy to present within one-half second of the target response. If the reinforcer used is a food item it should be something that can be quickly consumed by the child. For example if it takes a child one minute to chew and eat his reinforcer during a ten minute lesson discrete trial lesson the child will spend 80% of their time chewing and only 20% of their time learning. Alternately, a food item that can be consumed within five seconds will allow the child to spend 80% of their time learning and only 20% on chewing and eating the reinforcer. If the reinforcer is a toy or an activity it should be something that is easily removed. In other words if a child is given a toy that is difficult to remove this may result in a melt-down at which point more time is spent in calming the child down than learning within a given session (for such difficulties a BCBA can assist with options and decide how to address the behavior). Moreover, it is a good lesson for a child to learn to take away a preferred reinforcer and wait patiently until they receive the reinforcer again.
  5. Establish conditioned reinforcers: Conditioned reinforcers become “conditioned” due to a history of being paired with already effective reinforcers and include things like praise, playing with toys and earning money. In the natural environment many behaviors are maintained through conditioned reinforcers. Therefore if we want the child to be independent and successful in their natural environments a variety of conditioned reinforcers must be established. To establish a conditioned reinforcer, a neutral stimuli (such as social praise and smiles) must be paired with an already effective reinforcer (like food). Over time social praise will take on some of the reinforcing qualities of effective reinforcers (such as bouncing, tickling, etc.) and may begin to function as an effective reinforcer for a specific and other behaviors. In natural environments following adult commands, directions, instructions, etc., is followed mostly by social praise. So it is crucial to a child’s success that social praise become established as a conditioned reinforcer.
  6. Provide frequent reinforcement for appropriate behavior throughout the session/day: It is easy to simply expect a child to engage in appropriate behavior. Over time a therapist/parent/teacher may find themselves forgetting to reinforce particular behavior(s). Example: A child has been in therapy for approximately 3 months and has learned to respond to simple compliance instructions such as “come here”. The therapist says, “come here” and the child immediately stops what they are doing and goes to the therapist. The therapist than says “sit down” and the child immediately sits down. Although the child complied with both directions the therapist failed to provide reinforcement for the correct target response. If this occurs consistently over time the child’s responses to these simple instructions will likely decrease. Alternately, if the child is provided with a tangible reinforcer for their compliance than the behavior is likely to increase. Every moment of a teaching session is an opportunity to reinforce and therefore increase appropriate behavior. It is crucial to look for these opportunities and provide frequent reinforcement for appropriate behavior with the caveat that once a child has acquired or mastered a particular behavior it is not required to reinforce every instance of that behavior or response to maintain it. The frequency of reinforcement for a particular behavior will be determined by the schedule of reinforcement created by the BCBA.

Procedure for Conducting a Preference Assessment:

One method for conducting preference assessments is to present items in an array. These items can be presented in a box, on a table or on the floor. After the child selects one of these items and engages with it for several seconds remove the selected item and present the child with the remaining items. The second item the child selects will be the second most preferred item and so on and so forth until all items have been selected or until the child has stopped selecting. These items will then be used as reinforces from the most preferred to the least preferred in the next teaching session.

A preference assessment should be conducted at the start of each lesson within a given session.

Similarly another method is a mini assessment, where the child is once again presented with an array, however this time after the child selects and engages with the first item, the assessment stops and the lesson begins.

There are other assessment methods and if a child does not respond well to this method the BCBA can offer alternate methods of assessing.

What are Continuous and Intermittent Schedules of Reinforcement?

A schedule of reinforcement establishes the probability that a specific behavior will produce reinforcement. This means that it identifies how often reinforcement will be provided for a specific behavior.  There are two basic schedules of reinforcement: continuous and intermittent.

Continuous schedule: As indicated a continuous schedule of reinforcement means that every occurrence of a specific behavior will be reinforced. Continuous reinforcement is used when establishing or teaching new behaviors. Behaviors that the child is learning but has not yet mastered. These behaviors are said to be “on acquisition”, for example, if a child is learning to tie their shoes reinforcement would be provided every time the child tied their shoes. Over time praise may be given only when the child ties their shoes without assistance, and then once the child is doing so independently and correctly consistently at which time the BCBA may determine that tying shoes is mastered. At that point the schedule may move to an intermittent schedule of reinforcement.

Intermittent schedule: In an intermittent schedule only some occurrences of a specific behavior are reinforced, but not all of the instances. Intermittent schedules can be used to maintain behaviors that are already established or mastered. These behaviors are said to be “on maintenance”. In the shoe tying scenario, if an intermittent schedule is used it may be that only every third independent shoe tying behavior is reinforced. This schedule of reinforcement will be determined by the BCBA.

How Does the Type of Reinforcer and the Schedule of Reinforcement Change as a Child Progresses?

Naturally,  both the type of reinforcer and schedule of reinforcement will change as a child progresses through their program. In general reinforcers will move from primary/unlearned reinforcers to conditioned/learned reinforcers and the schedule will progress from continuous to intermittent.

Progression will also be made from the use of contrived reinforcers to the use of natural reinforcers. In natural environments, adults do not usually give children crackers, cookies or start blowing bubbles when they do things such as saying “hi” to another child, answer another child’s question, or join in on a conversation. When the skill of greeting another child is first taught, or responding to another child contrived primary/secondary reinforcers might be used to establish the behavior. However, autistic children will only continue to greet peers or answer peers when therapists are not present if we are able to transfer from contrived to natural occurring reinforcers. A natural reinforcer is the reinforcer that maintains a specific behavior in natural environments. For example, the natural reinforcer for saying hi to a peer would be that peer saying “hi” back.

The BCBA will determine the progression of both type of reinforcer and schedule of reinforcement.

How to Identify the Consequence that Follows No Response or an Incorrect Response?

Reinforcement is the consequence following a correct response, however an error correction procedure is required for incorrect responses or for no response.

An error correction procedure helps a child to learn a correct response. It is implemented when, in the presence of a specific SD, no response or an incorrect response has been made by the child. Implementing an error correction procedure provides an opportunity for the child to engage in a correct response, thereby decreasing the likelihood of the child demonstrating an error response in the future. In practice, an error correction procedure helps a child learn the correct response in the presence of the target SD.

Error correction procedures typically include a prompt (anything you say or do, in addition to the SD, to help the child respond correctly), and may include an informational “no” (simply saying “no” in a neutral tone of voice) to inform the child that they are incorrect.

There are multiple error correction procedures available for teaching.


The consistent use of consequences is critical to learning. The consistent presentation of appropriate consequences  effects the future frequency of the response. If a specific response produces reinforcers than it will increase in frequency over time. Likewise, if a specific behavior does not produce reinforcers, or if it produces an error correction procedure it will decrease over time.

Reinforcement is also critical to establishing stimuli as discriminative stimuli or SDs. An SD is a stimulus, in the presence of which a particular response will be reinforced, and in the absence of which that response will not be reinforced. A stimulus becomes an SD when a response is reinforced in its presence but not in its absence. It is important that stimuli be established as SDs, as we want particular responses to occur in the presence of particular stimuli or SDs. For example, we want the child to sit in the presence of the verbal stimuli “sit”, “come here” or “what’s your name?”. Reinforcing particular behaviors in the presence of particular SDs that we want to evoke that response, and by withholding reinforcement or implementing an error correction procedure, when the response occurs in the absence of the specific stimuli ensures that this happens. When this is done the response is under appropriate stimulus control, that is the appropriate stimuli or SDs evoke the correct response.

Reinforcement plays a critical role in establishing SDs.

The Intertrial Interval

The Intertrial Interval and the optimal rate of presenting SDs in a trial, which is referred to as instructional pacing.

What is Intertrial Interval?

The intertrial interval is the time between the end of one trial and the start of the next. This is sometimes referred to as the “between trials interval”.

Each trial consists of an Antecedent (in the form of an SD and/or an EO) a Response and a Consequence (in the form of an SR or an EC). The time period between the reinforcement (SR) or the error correction (EC) in one trial and the presentation of the SD or EO in the next trial is the intertrial interval.


The therapist presents the SD “Give me the blue cup” (in which an array of colored cups has been set up). The child responds correctly by giving the therapist the blue cup. The therapist provides the consequence of a small food item. After approximately one second the therapist presents the next SD.

The time period between the small food item consequence and the presentation of the next SD is the intertrial interval. This pause helps define for the child that one trial has ended and the next has begun.

Duration and Guidelines of an Intertrial:

The intertrial interval should be long enough to ensure that each trial is distinct but not so long that you lose the child’s attention. As a general guideline the interval should be no more than 2 seconds.

This two second guideline is based on research in the field of behavior analysis which has shown that:

  1. Fast rates of presenting SDs result in less disruptive behavior than slow presentation rates. The duration of the intertrial interval effects the rate at which SDs are presented or the pace of the session. So shorter intertrial intervals results in a faster pace of presentation of SDs and will likely result in fewer disruptive behaviors.
  2. The goal is to help the child catch up as much as possible to their typically developing peers so time is of the essence. Each trial is a learning opportunity for a child, therefore the more trials presented the more opportunities for learning for the child.

Each child is unique and the intertrial interval will often be guided by that child’s unique abilities and the particular lesson being taught. However, presenting SDs at a fast pace results in more successful and effective teaching sessions.

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Skill Repertoire Building Procedures