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High-Probability Request Sequence & Behavioural Momentum

What Is The High-Probability Request Sequence?

The high-probability request sequence (high-p) is a non-aversive antecedent intervention where the instructor presents easy tasks that the client consistently does on their own, quickly, before presenting the task that the client does not do. During the high-p request sequence, the learner comes in to contact with reinforcers to encourage continued responding.

High-probability: history of learner compliance, easy to do, and quick to complete
Low-probability: history of learner non-compliance, more difficult task, and defiant behaviours

What Is Behavioural Momentum?

Behavioural Momentum is measured by the rate and persistence of responses. Behavioural Momentum is commonly referred to when a behaviour (client responding) is repeated at a quick and consistent rate. One of the effects of the high-p request sequence is that the reinforcer for non-compliance (escape) to the low-p request is reduced.

Why Do We Use The High-Probability Request Sequence?

Effects of the high-p request sequence include an increase in socially appropriate behaviours and a reduction in defiant behaviour, non-compliance, and escape-related behaviour relating to task completion, as well as a decrease in transition problems in learners.

The high-p request sequence has also been shown to decrease the slowness in client responding to low-p requests. The behavioural momentum created by the high-p requests encourages the client to persist with the more difficult, low-p request.

Use our FREE High-Probability Tracking Sheet to keep an up-to-date list of targets for common skill areas!

How Do We Use The High-Probability Request Sequence?

Start by making a list of high-p requests for your learner. This can include motor movements or verbal responses the client can complete independently and will do without hesitation or non-compliance, 100% of the time. Then use these high-p requests, presenting 2 to 5 quickly to the learner before the low-probability request.

It is important that differential reinforcement is used while implementing a high-p request sequence. This means that non-compliance must be placed on extinction. Compliance with high-probability requests must be reinforced immediately after each response (e.g., verbal praise), and compliance with the low-probability request must be reinforced immediately with a powerful reinforcer (i.e., a jellybean).

While running instructional programs with clients, be sure to present the high-p request sequence at the beginning and throughout the session. This helps reduce the chance that challenging behaviours will provide the client with reinforcement.

Once you have identified a task as being a low-probability request (i.e., the client engages in escape-related behaviours), it is time to implement the high-p request sequence!


The student consistently engages in escape-related or tantrum behaviours while practicing for their spelling test.

Type of Request SD Response Reinforcer
High-P Request 1 “Write your name” Student writes name “Great job!”
High-P Request 2 “Write the date” Student writes date “Excellent work!”
High-P Request 3 “Underline the first word” Student underlines first word “Amazing!”
Low-P Request “Copy the first word” Student copies first word “Wow! Here is a jellybean!”

Be Mindful…

There should be no breaks between instructions, the goal for the high-p request sequence is to work from the behavioural momentum created by the high-p requests.

If a client engages in problem behaviours, refrain from using the high-p request sequence immediately. We do not want the client to learn that non-compliance gains them access to easier requests.
Make sure to check out our blog on Following Through!

Do not only provide high-p requests to clients. Instructors may be tempted to avoid escape-related or non-compliant behaviours associated with the low-p requests such as aggression or self-injury. Be aware of your clients needs and abilities, and prepare for challenging behaviours, but do not avoid the low-p requests.


2 thoughts on “High-Probability Request Sequence & Behavioural Momentum”

  1. Pingback: Shaping Behavior Using ABA - How to ABA

  2. Pingback: Error Correction Procedure and Transfer Trial - How to ABA

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