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ABA Concepts

Schedules of Reinforcement: VR, FR, VI, FI Compared

Schedules of reinforcement describe the rule that determines which responses are followed by reinforcement, and they strongly influence response rate, pause patterns, and resistance to extinction. This guide compares the four basic intermittent schedules: fixed ratio (FR), variable ratio (VR), fixed interval (FI), and variable interval (VI). You will learn the defining features, typical response patterns such as post-reinforcement pauses and scallops, real-life examples like piecework pay, slot machines, checking email, and scheduled exams, and how each schedule applies in clinical programs. We also cover continuous reinforcement, extinction, thinning schedules, ratio strain, and compound schedules such as multiple, mixed, chained, and concurrent. Clear examples and a quick decision guide help you identify schedules in exam scenarios. Use this comparison to select appropriate schedules for skill acquisition, maintenance, and reduction of problem behavior with confidence.

July 15, 2024

What Is a Schedule of Reinforcement?

A schedule of reinforcement is a rule that specifies when a response will be reinforced. Schedules were extensively studied by Ferster and Skinner and they produce characteristic patterns of behavior. Understanding them helps you build new skills, maintain them in the natural environment, and diagnose why problem behavior persists.

The simplest schedule is continuous reinforcement (CRF), in which every response is reinforced. CRF is best for acquiring new behavior. Intermittent reinforcement (INT) reinforces some, but not all, responses and is better for maintenance. Extinction is the opposite of CRF: no response is reinforced.

The four basic intermittent schedules vary along two dimensions. Ratio schedules depend on the number of responses. Interval schedules depend on the passage of time, followed by one response. Each can be fixed (constant requirement) or variable (changing around an average).

Fixed Ratio (FR)

In a fixed ratio schedule, reinforcement is delivered after a set number of responses. FR 5 means every fifth response is reinforced.

  • Response pattern: High, steady rates of responding, followed by a post-reinforcement pause (PRP). The pause tends to be longer when the ratio requirement is larger. After the pause, the learner shows a rapid ratio run until reinforcement.
  • Examples: Piecework pay (paid per ten items assembled), a student earning a sticker after every five completed worksheets, a coffee shop punch card.
  • Clinical use: Token economies often use fixed ratio requirements, such as five tokens for a reward.

Variable Ratio (VR)

In a variable ratio schedule, reinforcement is delivered after an average number of responses, which varies from reinforcer to reinforcer. VR 10 means on average every tenth response is reinforced, but the actual number might be 3, 15, 8, and so on.

  • Response pattern: High, steady rates of responding with little or no post-reinforcement pause, since the next response could always produce reinforcement.
  • Examples: Slot machines, fishing, sales calls, checking a lottery scratch ticket, playing a game with random rewards, and many problem behaviors that parents occasionally reinforce.
  • Resistance to extinction: VR schedules produce behavior that is highly resistant to extinction. This is why occasional giving in to tantrums can make them persistent.
  • Clinical use: After a skill is acquired, VR schedules are used to maintain it, because they promote steady performance and resistance to extinction.

Fixed Interval (FI)

In a fixed interval schedule, the first response after a set amount of time has elapsed is reinforced. FI 60 seconds means that the first response after 60 seconds is reinforced, and responses during the interval have no effect.

  • Response pattern: A scallop. Responding is low or absent early in the interval and accelerates as the end of the interval approaches. There is a post-reinforcement pause.
  • Examples: Studying for a scheduled weekly exam, with studying rising as the exam gets near; checking the oven as the baking time approaches; a paycheck every two weeks (though pay is not contingent on a response in the same way).
  • Clinical use: FI-like arrangements appear in classrooms with periodic quizzes. They tend to yield lower overall response rates than ratio schedules.

Variable Interval (VI)

In a variable interval schedule, the first response after an average amount of time is reinforced, and the length of the interval varies. VI 30 seconds means intervals average 30 seconds.

  • Response pattern: Moderate, steady responding with few pauses.
  • Examples: Checking email or social media for new messages, checking your mailbox, pop quizzes, a teacher randomly checking on students and reinforcing on-task behavior.
  • Resistance to extinction: High, similar to VR but with lower rates.
  • Clinical use: VI schedules are well suited for maintaining behaviors such as on-task behavior, where steady rather than burst responding is desired.

Comparing the Four

  1. Response rate: Ratio schedules (FR and VR) produce higher rates than interval schedules (FI and VI), because reinforcement depends directly on response number.
  2. Pausing: FR and FI produce post-reinforcement pauses; VR and VI produce steady responding.
  3. Resistance to extinction: Variable schedules (VR and VI) generally produce greater resistance to extinction than fixed schedules.
  4. Typical patterns: FR yields pause-run patterns; VR yields steady high rates; FI yields scallops; VI yields steady moderate rates.

Related Schedules

Duration and time-based schedules

  • Fixed duration (FD) and variable duration (VD): Reinforcement follows continuous engagement in the behavior for a set or average amount of time.
  • Fixed time (FT) and variable time (VT): Reinforcement is delivered after a period of time regardless of behavior. These are noncontingent reinforcement schedules.
  • Limited hold: The reinforcer is available only for a limited time after the interval elapses.

Differential reinforcement schedules

  • DRL: Reinforcement for responding at a low rate.
  • DRH: Reinforcement for responding at a high rate.
  • DRO: Reinforcement for the absence of the behavior during an interval.

Compound schedules

  • Multiple: Two or more schedules alternate, each signaled by a distinct stimulus.
  • Mixed: Like multiple schedules, but without signals.
  • Chained: Responses must be completed in a sequence, with a signal for each component, and reinforcement follows the last component.
  • Tandem: Like chained schedules, without distinct signals.
  • Concurrent: Two or more schedules operate simultaneously on different response options, which is relevant to the matching law and choice.

Thinning Schedules and Ratio Strain

When moving from CRF to intermittent reinforcement, thin gradually. For example, move from CRF to FR 2, to FR 3, and then to VR 5. If the schedule is thinned too quickly, behavior may deteriorate, a phenomenon called ratio strain. Signs include increased pausing, reduced responding, frustration, or problem behavior. The solution is to return to a richer schedule and thin more slowly.

Applications in Treatment

  • Acquisition: Begin with CRF and prompts to build behavior quickly.
  • Maintenance: Shift to intermittent schedules that match natural contingencies, and pair with praise and natural reinforcers.
  • Problem behavior: Avoid unplanned intermittent reinforcement, especially VR, since it produces durable behavior. Extinction must be consistent, and caregivers should be trained to avoid giving in occasionally.
  • Functional communication training: Start with CRF for the replacement response, then thin by increasing delays or response requirements, using signals to indicate when reinforcement is unavailable.

Exam Strategies

  1. Ask: does reinforcement depend on number of responses (ratio) or time (interval)?
  2. Ask: is the requirement constant (fixed) or changing (variable)?
  3. Match the response pattern: pause-run for FR, steady high for VR, scallop for FI, steady moderate for VI.
  4. Remember that if a behavior is unusually resistant to extinction, a history of variable reinforcement is a likely cause.

Key Takeaways

FR, VR, FI, and VI differ in the rule for reinforcement and the behavior pattern they produce. Ratio schedules generate higher rates, variable schedules generate steadier responding and greater resistance to extinction, and fixed schedules generate pauses. Use schedules purposefully, thin gradually, and avoid accidental variable reinforcement of problem behavior.

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