By Matt Harrington, BCBA · Behaviorist Book Club · Research-backed answers for behavior analysts
Functional Communication Training is an evidence-based intervention for problem behavior that teaches a communicative response that produces the same reinforcer maintaining the challenging behavior. The core mechanism is competing operant allocation: when a communicative response is more efficient — producing reinforcement faster, with less effort, and more reliably than the problem behavior — behavior reallocates toward communication. FCT does not suppress challenging behavior directly; it makes challenging behavior functionally unnecessary by providing a more efficient pathway to the same outcome. This is why accurate functional assessment is a prerequisite to effective FCT design.
Dr. Fisher extended FCT from its foundational work by Carr and Durand in 1985 by deepening the theoretical understanding of FCT mechanisms and addressing the clinical challenges of schedule thinning and generalization. His research program at the Munroe-Meyer Institute applied behavioral economic and matching law frameworks to FCT, explaining why specific reinforcement schedule parameters produce specific patterns of behavior allocation. He developed systematic protocols for thinning FCT reinforcement schedules while maintaining suppression of challenging behavior — a clinical challenge that had limited the durability of FCT outcomes in earlier research.
FCT is only effective when the communicative response is matched to the function maintaining the challenging behavior. If challenging behavior is maintained by escape from demands but FCT teaches an attention-requesting response, the escape function remains unaddressed and the challenging behavior will persist. Multiple studies have demonstrated that non-function-matched communicative responses do not reduce challenging behavior while function-matched responses do — a finding that directly establishes functional assessment as a prerequisite. BCBAs who implement FCT without functional assessment are applying the procedure without the information needed to design it correctly.
The efficiency principle holds that the FCT response must be more efficient than the challenging behavior on key parameters: response effort (the FCT response should require no more effort than the problem behavior), reinforcement delay (the FCT response should produce reinforcement at least as quickly), and reinforcement quality (the FCT response should produce reinforcement of equivalent or superior quality). Fisher's research demonstrates that when the FCT response is less efficient than the challenging behavior on any of these dimensions, challenging behavior continues to compete successfully and behavior does not fully reallocate toward communication.
Schedule thinning involves gradually reducing the density of reinforcement for the FCT response — moving from continuous reinforcement during initial training to intermittent schedules compatible with natural environments. The primary risk during schedule thinning is resurgence: the reappearance of previously suppressed problem behavior as the FCT schedule becomes thinner. Fisher's research has identified that thinning too rapidly or using abrupt ratio increases is associated with greater resurgence. Data-based thinning protocols — advancing the schedule only when problem behavior remains at criterion — reduce this risk and produce better long-term outcomes.
FCT responses can be vocal (words or phrases), gestural (signs or natural gestures), graphic (picture exchange, PECS cards), or high-tech AAC (speech-generating devices). The selection depends on the learner's current communication repertoire, the effort required by each modality, and the recognizability of the response by natural communication partners across environments. FCT is most effective when the response modality is one the learner can already perform or acquire quickly, and when communication partners in all relevant settings are trained to respond consistently to that modality.
The matching law predicts that behavior allocates proportionally to the relative reinforcement available for competing responses. In an FCT framework, the challenging behavior and the communicative response are two competing responses with potentially different reinforcement schedules. The matching law predicts that if the FCT response produces reinforcement on a richer, more immediate schedule than the challenging behavior, behavior will allocate predominantly toward the communicative response. Fisher's application of matching law logic to FCT provided a theoretical account that explains not only when FCT works but what specific schedule parameters produce specific patterns of behavior allocation.
Generalization of FCT to natural environments requires that multiple dimensions transfer simultaneously: the communicative response must occur across settings (clinic, home, school, community), across communication partners (parents, teachers, peers, community members), across motivating operation states (at various levels of deprivation or satiation), and without the intensive prompt support available during initial training. Achieving this requires planned generalization programming — training in multiple settings, training multiple communication partners, using common stimuli from natural environments, and conducting systematic generalization probes before considering FCT complete.
Code 2.01 requires using evidence-based practices and practicing within areas of competence — FCT requires functional assessment competency and knowledge of schedule design. Code 6.01 requires recommending the least intrusive effective intervention — FCT is inherently less restrictive than consequence-based procedures because it builds the communicative repertoire. Code 4.07 requires BCBAs to ensure supervisees implement plans with treatment integrity — FCT fidelity is critical because inconsistent reinforcement of the communicative response or inadvertent reinforcement of the problem behavior can undermine outcomes. Code 3.11 requires documenting treatment decisions, including the functional assessment rationale for FCT design.
Resurgence refers to the reappearance of previously suppressed challenging behavior under conditions of increased extinction or reduced reinforcement of the FCT response — typically during schedule thinning. Resurgence is predicted by behavioral theory: when a previously reinforced response (the problem behavior) is placed on extinction while an alternative response (the FCT response) has its reinforcement schedule thinned, the probability of resurgence increases. Fisher's research has examined conditions that predict resurgence magnitude and identified schedule thinning procedures that minimize it, including gradual ratio increases, chained schedule approaches, and the use of multiple schedules with discriminative stimuli.
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All behavior-analytic intervention is individualized. The information on this page is for educational purposes and does not constitute clinical advice. Treatment decisions should be informed by the best available published research, individualized assessment, and obtained with the informed consent of the client or their legal guardian. Behavior analysts are responsible for practicing within the boundaries of their competence and adhering to the BACB Ethics Code for Behavior Analysts.