What Is Intermittent Reinforcement in ABA Therapy?
Intermittent reinforcement is the delivery of reinforcement after some, but not all, instances of a behavior. It sits between two ends of a spectrum: continuous reinforcement, where every instance of a behavior is reinforced, and extinction, where the behavior is never reinforced. Intermittent schedules of reinforcement are one of the most studied topics in behavior analysis, and the way reinforcement is scheduled has powerful effects on how behavior is acquired, how stable it becomes over time, and how it responds when reinforcement eventually stops.
Behavior analysts typically use continuous reinforcement when a learner is first acquiring a skill, then shift to intermittent reinforcement as the skill becomes established. Behavior technicians implement the schedules across daily sessions, and the therapist working with the family supports schedule consistency at home. The ASD Toddler Initiative at the University of North Carolina Frank Porter Graham Child Development Institute describes this sequence clearly: once a toddler learns the behavior and meets a pre-established criterion, reinforcement can be delivered intermittently to help maintain the skill over time. The shift from continuous to intermittent reinforcement is one of the most important transitions in any ABA program.
Intermittent reinforcement schedules come in two main families. Ratio schedules deliver reinforcement based on the number of responses (every fifth response, on average every fifth response, and so on). Interval schedules deliver reinforcement based on the passage of time (the first response after a set amount of time, the first response after a variable amount of time). Both ratio and interval schedules can be either fixed (the requirement is always the same) or variable (the requirement changes around an average). The four combinations produce distinctive patterns of behavior that behavior analysts can predict and use.
One of the most consequential properties of intermittent reinforcement is that behaviors built up through intermittent schedules tend to be more resistant to extinction than behaviors built up through continuous reinforcement. A behavior that has been reinforced every time it occurs may drop off quickly when reinforcement stops; a behavior that has been reinforced unpredictably persists much longer. This property is a tool for the behavior analyst when the goal is durable maintenance, and a hazard when the goal is reducing an interfering behavior that has been accidentally reinforced on an intermittent schedule.
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Examples of Intermittent Reinforcement in ABA Therapy
Example 1: Thinning the schedule after acquisition
A behavior technician has been teaching a four-year-old client to use a one-word request (“Help”) when she needs assistance. During acquisition, every successful request earned immediate help (continuous reinforcement). Once the learner is requesting reliably across sessions, the behavior analyst designs a schedule-thinning plan and the technician carries it out: she begins reinforcing every second request, then every third, then on a variable ratio averaging about four requests per reinforcement. The behavior maintains as the schedule thins because the learner has built a strong history with the response. This kind of positive reinforcement schedule progression is one of the most common applications of intermittent reinforcement in ABA programs.
Example 2: Variable-interval schedule for sustained engagement
A behavior analyst designs a program to increase the duration a six-year-old client stays on-task during academic work. The behavior technician uses a variable-interval schedule: the technician sets a timer that beeps at unpredictable intervals averaging two minutes apart, and the technician reinforces the learner whenever he is engaged in the task at the moment the timer beeps. Because the learner can’t predict when reinforcement will come, he sustains attention more evenly across the session rather than working hard only just before a predictable reinforcement opportunity. Variable schedules tend to produce this kind of steady, stable responding, and the technician collects data on engagement duration so the analyst can adjust the schedule as needed.
Example 3: Identifying an accidentally intermittent schedule for interfering behavior
A behavior analyst is consulting with a family whose seven-year-old client engages in escalating tantrums when denied access to a tablet. The behavior technician working with the learner and the family observe that the parents usually hold the limit, but about one time in eight, they give in when the tantrum becomes too intense. The behavior analyst recognizes this as an accidentally intermittent reinforcement schedule: the tantrum is being reinforced unpredictably, which makes it especially persistent. The family’s consistency may have actually been making the problem more durable. The behavior analyst designs a plan that combines extinction (no tablet access for tantrums, ever) with reinforcement of an appropriate request, and the technician coaches the family on the consistency the new plan requires.
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Why Is Intermittent Reinforcement Important in ABA?
Intermittent reinforcement matters because no skill is genuinely useful if it only happens when reinforcement is available every single time. Real life doesn’t work that way. A learner who has only been taught to say “please” when reinforcement is reliably delivered will stop saying “please” when the world starts responding less predictably. Building behavior under intermittent schedules prepares the learner for the natural reinforcement contingencies they’ll encounter outside of structured teaching. This is one reason schedule-thinning is built into virtually every ABA program after initial skill acquisition.
Intermittent reinforcement also connects directly to the idea of maintenance. A behavior is maintained when it persists across time, settings, and the absence of immediate reinforcement. Schedule-thinning is one of the primary tools for promoting maintenance, alongside generalization training and reinforcer variation. The behavior analyst tracks the learner’s performance as the schedule thins and adjusts the pacing based on the data, while behavior technicians carry out the schedule changes session by session. Too fast a thinning produces deterioration; too slow a thinning leaves the learner dependent on continuous reinforcement that won’t exist in everyday environments. For more on the broader path of skill-building in an ABA program, read our blog on how long will my child be in ABA.
The persistence-under-extinction property of intermittently reinforced behavior also has clinical implications when the team is reducing interfering behavior. Behaviors that have been accidentally reinforced on intermittent schedules (the occasional giving-in to a tantrum, the occasional response to an attention-getting behavior) are typically much harder to extinguish than behaviors that have been continuously reinforced. The team plans for what’s sometimes called an extinction burst, a temporary increase in the behavior’s intensity or frequency when reinforcement stops, and the family is prepared in advance so the plan can be maintained through that period.
Different reinforcement schedules also produce distinctive patterns of behavior, and choosing the right schedule for the goal matters. Variable-ratio schedules produce high, steady rates of responding (which is why gambling can be so durable). Fixed-ratio schedules produce burst-and-pause patterns. Variable-interval schedules produce steady, moderate rates. Fixed-interval schedules produce scallop patterns with low responding right after reinforcement and high responding just before. The behavior analyst selects the schedule that produces the response pattern best suited to the skill being taught and the context it’ll be used in. The conditioned reinforcer being used (a token, praise, a check on a chart) often interacts with the schedule choice.
Schedule thinning typically starts early in an ABA program, sometimes as soon as a skill is reliably acquired. For families of young children just entering services, understanding that reinforcement won’t always look the same as it does in the first weeks of intervention can help set realistic expectations. For more on what early intervention looks like and why early gains matter, read our blog on 5 benefits of early intervention.
FAQs About Intermittent Reinforcement
What’s the difference between continuous and intermittent reinforcement?
Continuous reinforcement delivers reinforcement after every instance of the target behavior. Intermittent reinforcement delivers reinforcement after some instances but not others. Continuous reinforcement is generally used during skill acquisition, when the learner is first building a new behavior and needs strong, predictable feedback. Intermittent reinforcement is used during maintenance, when the goal is to keep the behavior strong over time without requiring reinforcement every single time. Most ABA programs move from continuous to intermittent reinforcement systematically as a skill becomes established.
What are the four main types of intermittent reinforcement schedules?
Fixed-ratio (FR) schedules deliver reinforcement after a set number of responses (every fifth response). Variable-ratio (VR) schedules deliver reinforcement after an average number of responses (an average of every fifth response, varying around that). Fixed-interval (FI) schedules deliver reinforcement for the first response after a set amount of time has passed. Variable-interval (VI) schedules deliver reinforcement for the first response after a variable amount of time has passed (averaging around a target). Each produces distinctive patterns of behavior, and the behavior analyst chooses based on what pattern the skill calls for.
Why does intermittent reinforcement make behavior more resistant to extinction?
When reinforcement is continuous, the absence of reinforcement is an obvious signal that something has changed. When reinforcement is intermittent, an unreinforced response feels routine, because the learner is used to many responses going unreinforced. This makes it harder for the learner to detect that extinction has begun, so the behavior persists longer. The effect has been demonstrated repeatedly in basic behavior research and has direct implications for clinical work, both when building durable target behaviors and when reducing accidentally reinforced interfering behaviors.
How do behavior analysts decide when to thin a reinforcement schedule?
The decision is data-driven. The behavior analyst typically thins the schedule after the learner has acquired the behavior reliably under continuous reinforcement, with mastery criteria like “90 percent accuracy across three consecutive sessions” or similar. Thinning then proceeds gradually, with data monitoring at each step. If the behavior deteriorates, the analyst may pause or reverse the thinning. The pace of thinning depends on the learner, the skill, and the context the skill will be used in.
Can intermittent reinforcement accidentally strengthen interfering behavior?
Yes, and this is a common clinical concern. When parents or caregivers respond to a behavior inconsistently, sometimes giving in and sometimes holding the limit, they may be unintentionally delivering intermittent reinforcement. The resulting behavior tends to be especially persistent and harder to reduce than if the behavior had been consistently reinforced and then put on extinction. Behavior analysts often work with families on consistency precisely because of this dynamic. The good news is that recognizing the pattern is the first step toward changing it.
Key Takeaways About Intermittent Reinforcement
- Intermittent reinforcement is the delivery of reinforcement after some but not all instances of a behavior, sitting between continuous reinforcement and extinction.
- Behavior analysts typically use continuous reinforcement during skill acquisition and shift to intermittent reinforcement to maintain the skill over time.
- The four main intermittent schedules are fixed-ratio, variable-ratio, fixed-interval, and variable-interval, each producing distinctive patterns of behavior.
- Behaviors built up through intermittent reinforcement tend to be more resistant to extinction than behaviors built up through continuous reinforcement.
- Schedule thinning is data-driven and gradual; too fast a thinning produces deterioration, too slow leaves the learner overly dependent on dense reinforcement.
- Accidentally intermittent reinforcement of interfering behavior (occasional giving-in) makes that behavior especially persistent, which is one reason consistency matters in ABA programs.
