Why Schedules of Reinforcement Matter
Schedules of reinforcement are one of the most heavily tested topics on the BCBA exam. Understanding how different schedules produce different patterns of responding is essential for both passing the exam and making informed clinical decisions. A reinforcement schedule specifies the rule governing which instances of behavior will be followed by reinforcement.
Continuous vs. Intermittent Reinforcement
Under a continuous reinforcement (CRF) schedule, every instance of the target behavior is reinforced. CRF is typically used during the acquisition phase of skill building because it produces rapid learning. However, behaviors maintained on CRF extinguish quickly when reinforcement is withdrawn.
Under intermittent reinforcement, only some instances of the behavior are reinforced according to a specific schedule. Behaviors maintained on intermittent schedules are more resistant to extinction, a phenomenon known as the partial reinforcement extinction effect (PREE).
The Four Basic Intermittent Schedules
Fixed Ratio (FR)
Reinforcement is delivered after a fixed number of responses. An FR-5 schedule delivers reinforcement after every 5th response. FR schedules produce a high, steady rate of responding with a brief post-reinforcement pause. The higher the ratio requirement, the longer the post-reinforcement pause.
Clinical example: A student earns a sticker after completing every 10 math problems (FR-10). You observe a characteristic "break-and-run" pattern where the student pauses briefly after earning the sticker before rapidly working through the next set of problems.
Variable Ratio (VR)
Reinforcement is delivered after an unpredictable number of responses that average to a specified value. A VR-5 schedule delivers reinforcement after an average of 5 responses, but the actual number varies from trial to trial. VR schedules produce the highest, most consistent rate of responding with little to no post-reinforcement pause.
Clinical example: A therapist provides praise after an average of 4 correct social initiations (VR-4). Because the child cannot predict exactly when praise will come, social initiations remain consistently high throughout the session.
Fixed Interval (FI)
Reinforcement is delivered for the first response that occurs after a fixed period of time has elapsed. Under an FI-2 minute schedule, the first response after 2 minutes produces reinforcement. FI schedules produce a "scallop" pattern: low responding immediately after reinforcement, gradually increasing as the interval end approaches.
Clinical example: A teacher checks student work every 30 minutes and provides feedback for whatever progress has been made since the last check (FI-30 min). Students show increasing effort as the 30-minute mark approaches.
Variable Interval (VI)
Reinforcement is delivered for the first response after a variable amount of time that averages to a specified value. A VI-3 minute schedule delivers reinforcement for the first response after an average of 3 minutes. VI schedules produce a moderate, steady rate of responding.
Clinical example: A supervisor observes a behavior technician at unpredictable times averaging once per hour (VI-60 min) and provides performance feedback for correct implementation observed at the moment of observation.
Compound Schedules
Compound schedules combine two or more simple schedules to govern reinforcement delivery.
Multiple Schedule
Two or more basic schedules alternate, each associated with a different discriminative stimulus. The individual can distinguish between schedule components based on the stimulus present. Example: in the presence of a green card (SD), an FR-5 is in effect; in the presence of a red card, a DRO 2-minute schedule is in effect.
Mixed Schedule
Similar to a multiple schedule, but without discriminative stimuli signaling which component is in effect. The individual cannot predict which schedule is currently active.
Concurrent Schedule
Two or more schedules operate simultaneously for two or more different behaviors. This is the basis for the matching law, which states that the relative rate of responding to each alternative matches the relative rate of reinforcement obtained from each.
Chained Schedule
Two or more schedules are presented in sequence, each with its own discriminative stimulus. Completion of one schedule component produces the discriminative stimulus for the next component, and reinforcement is delivered only upon completion of the final component.
Tandem Schedule
Like a chained schedule but without discriminative stimuli for each component.
Schedule Thinning in Clinical Practice
Schedule thinning is the systematic process of gradually increasing the response requirement or interval length from a denser to a leaner schedule. This is a critical clinical skill, especially when fading reinforcement after skill acquisition or when transitioning from functional communication training to more naturalistic contingencies.
Common schedule thinning errors include thinning too quickly (which can produce extinction-like effects or resurgence of problem behavior) and failing to thin at all (which creates dependency on dense reinforcement that cannot be maintained in natural environments).
Exam Tips for Schedule Questions
- Remember the relationship between ratio schedules and rate of responding: ratio schedules generally produce higher rates than interval schedules
- Variable schedules produce more consistent responding and greater resistance to extinction than fixed schedules
- Be able to identify each schedule from a clinical scenario description, not just from a definition
- Understand post-reinforcement pause patterns: present in FR and FI, minimal in VR and VI
- Know the matching law and its implications for concurrent schedules