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Understanding Behavioral Momentum Theory

Behavioral momentum theory describes how the persistence of behavior after a disruption is related to its history of reinforcement, much like a moving object resists changes in speed. This guide explains behavioral momentum in clear terms, including response rate versus resistance to change, the role of the stimulus-reinforcer relation, and why behavior with a rich reinforcement history persists even during extinction, satiation, or distraction. You will learn how the high-probability (high-p) request sequence applies momentum to increase compliance with low-probability requests, how to build an effective sequence, and when it can fail. We also discuss implications for treatment of problem behavior, including why reinforcement of alternative behavior can sometimes make problem behavior more persistent, and how to plan accordingly. Clinical examples, implementation steps, and BCBA exam tips will help you apply the theory accurately, avoid common pitfalls, and answer momentum-related questions with confidence.

April 15, 2024

The Momentum Metaphor

In physics, momentum is the product of mass and velocity. A heavy object moving quickly is harder to stop than a light object moving slowly. Behavioral momentum, introduced by John Nevin and colleagues, applies this metaphor to behavior. Behavioral rate is analogous to velocity, and resistance to change is analogous to mass. Behavior that has been reinforced often and richly in a given context shows greater resistance to change when it is disrupted.

Core Concepts

  • Response rate: How often the behavior occurs. This is analogous to velocity.
  • Resistance to change: How persistent the behavior is when something disrupts it, such as extinction, prefeeding, distractors, or punishment. This is analogous to mass.
  • Disruptors: Events that interfere with ongoing behavior.

A central finding is that resistance to change is determined by the rate of reinforcement in a stimulus context, not by the response rate itself. Behavior in a context with more frequent reinforcement is more persistent, even if the response rates are the same in both contexts. This is described as the stimulus-reinforcer relation, which is more important than the response-reinforcer relation for persistence.

The High-Probability Request Sequence

The most common clinical application is the high-probability (high-p) request sequence, also called a high-p instructional sequence. Here is how it works.

  1. Deliver a series of 2 to 5 easy requests that the learner is likely to follow (high-p requests), such as "Give me five," "Touch your nose," or "Clap your hands."
  2. Reinforce compliance immediately after each, usually with praise.
  3. Rapidly present the low-probability (low-p) request that has been difficult, such as "Put on your shoes."
  4. Reinforce compliance with the low-p request.

The theory is that the quick succession of reinforced compliance builds behavioral momentum that carries over into the less preferred task. The sequence should be delivered quickly, with short intervals between requests, because momentum fades if the pace slows.

Building an effective sequence

  • Verify the high-p requests: They should be followed about 80 percent of the time or more. Test them first.
  • Keep the pace fast: Intervals of a few seconds or less between requests work best.
  • Use reinforcement: Reinforce each compliance, particularly the low-p response.
  • Keep requests topographically different: A mix of vocal, motor, and object-related requests helps maintain interest.
  • Fade over time: As compliance with the low-p request becomes reliable, reduce the number of high-p requests.

When High-P Sequences Work Best

High-p sequences are most useful for noncompliance maintained by escape from demands, and for teaching new or nonpreferred routines such as transitions, hygiene, and academic tasks. They are an antecedent intervention and are generally fast acting. Research suggests they are most effective when combined with other procedures such as escape extinction for severe problem behavior.

Possible limitations

  • If the learner's problem behavior is not escape maintained, high-p sequences may have little effect.
  • If the high-p requests are not actually high probability, the sequence may not build momentum.
  • A slow delivery pace can undermine the effect.
  • If a learner begins to discriminate that a high-p sequence always precedes a difficult request, compliance with the high-p requests may fall.

Momentum and Treatment of Problem Behavior

Behavioral momentum research has produced an important and somewhat counterintuitive finding. When we reinforce an alternative behavior, such as in differential reinforcement of alternative behavior (DRA) or functional communication training, the added reinforcement in the same context can strengthen the stimulus-reinforcer relation and make the problem behavior more resistant to change, even though the rate of problem behavior has decreased. This can show up as relapse when treatment is disrupted, for example when reinforcement for the alternative response lapses or when a caregiver implements the plan inconsistently.

Implications for clinicians:

  • Plan for treatment integrity and train caregivers to deliver consequences consistently.
  • Combine reinforcement of alternatives with extinction of the problem behavior when feasible and safe.
  • Consider the amount of reinforcement for the alternative behavior and avoid unnecessary reinforcement in the context of problem behavior.
  • Anticipate relapse events such as extinction of the alternative response, and teach clients and caregivers how to respond.
  • Thin reinforcement gradually and monitor for resurgence.

Relation to Other Concepts

  • Premack principle: Uses a preferred activity as a consequence. High-p uses easy requests as an antecedent strategy.
  • Resurgence: The return of a previously reinforced behavior when a more recent behavior is placed on extinction. Momentum research helps explain why behaviors with strong histories come back.
  • Extinction: Behaviors with higher momentum take longer to extinguish.
  • Schedules: Intermittent reinforcement schedules produce behavior that is resistant to extinction, which is related but not identical to momentum.

Practical Example

A six-year-old resists cleaning up toys and often cries and drops to the floor. The behavior analyst identifies several high-p requests: "Give me a high five," "Show me your shoes," "Pick up the red block," and "Hand me the truck." She delivers these in rapid succession, reinforcing each with enthusiastic praise, then says, "Put the bin on the shelf." Compliance with the target request increases across sessions. After several weeks, she reduces the sequence to two high-p requests, then one, then to a normal request with praise.

BCBA Exam Tips

  • Know that behavioral momentum is about persistence of behavior and resistance to change, tied to reinforcement history.
  • Know the high-p sequence steps: several quick high-p requests, then the low-p request, with reinforcement.
  • Recognize that the high-p sequence is an antecedent strategy that does not depend on delivering a consequence for noncompliance.
  • Expect questions about why a behavior persists despite extinction or why problem behavior can return even after treatment success.

Key Takeaways

Behavioral momentum describes resistance to change as a function of reinforcement history in a context. The high-p request sequence applies this principle to build compliance, and the theory also warns that reinforcing alternatives within a context can increase the persistence of problem behavior if treatment integrity falters. Use the theory to plan interventions and anticipate relapse.

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