By Matt Harrington, BCBA · Behaviorist Book Club · Research-backed answers for behavior analysts
Emergent relations are stimulus-stimulus or stimulus-response relations that an organism demonstrates without having been directly trained to produce them. The classic example is stimulus equivalence: after training A→B and A→C matching relations, an organism may demonstrate B→C, C→B, B→A, and C→A without reinforcement for these specific relations. The theoretical significance lies in the challenge these phenomena pose to simple stimulus-response accounts of learning — they suggest that learned relations generalize in ways that go beyond the trained history, raising questions about the mechanism responsible and whether existing behavioral concepts adequately explain it.
A mediational account proposes that derived stimulus relations are explained by common mediating responses — either overt behaviors or covert verbal responses — that come to be conditioned to multiple stimuli during training, creating a bridge that produces the appearance of derived relations. Under this account, emergence is not a separate process but the product of standard conditioning mechanisms applied to shared mediators. Sidman's formulation treats equivalence as a fundamental behavioral phenomenon not reducible to mediating responses, emerging automatically when specific training conditions are met. The debate centers on whether mediational accounts can explain the data more parsimoniously or whether they fail to account for certain empirical findings.
Stimulus equivalence provides a behavioral account of how arbitrary symbolic relations — such as the relation between a spoken word, a written word, and the object it names — are established and generalized. In language programming, BCBAs can use equivalence-based training to expand a client's verbal repertoire more efficiently by training some relations and probing for derived ones rather than directly training every relation. A client trained to match spoken words to pictures and spoken words to objects may derive the picture-object relation without direct training, effectively tripling the productivity of a single training set. This has direct efficiency implications for comprehensive verbal behavior programs.
Relational Frame Theory (RFT) proposes that arbitrarily applicable relational responding — responding to stimuli in accordance with derived relations — is itself an operant behavior class that is learned through a history of multiple exemplar training. Under RFT, equivalence is not emergent in a mysterious sense but is an instance of a broader learned behavioral repertoire. RFT distinguishes between different relational frames (coordination, distinction, comparison, hierarchy) and proposes that complex human language and cognition emerge from histories of reinforced relational responding. Clinically, RFT suggests that clients who fail to form equivalence classes may benefit from training in the prerequisite relational responding skills.
Reliable demonstration of stimulus equivalence requires: a training structure that produces robust conditional discriminations (typically measured at 90% or higher accuracy), probe trials that have never been directly reinforced (to ensure derived relations are not simply trained relations in disguise), controls for position biases and generalized matching responses, sufficient intertrial intervals to prevent contextual cueing, and replication across sessions. The training structure matters — sample-as-node designs (A→B and A→C) and linear series designs (A→B and B→C) produce equivalence through different mechanisms and the choice between them should be deliberate.
When derived relations fail to emerge after appropriate equivalence training, BCBAs should first verify that the trained baseline relations meet accuracy criteria and that the probe design is procedurally sound. If training and probing are adequate, consider whether the client has the prerequisite conditional discrimination skills and relational learning history. Some clients may require direct training of failing derived relations before broader equivalence class formation can be established. Consulting the experimental literature on factors affecting equivalence formation — stimulus type, training structure, learning history — and discussing with a supervisor familiar with verbal behavior are appropriate next steps.
Parsimony — preferring explanations that account for the data with the fewest additional assumptions — is a core principle of scientific reasoning that Schlinger has applied systematically to behavior analytic theory. When evaluating competing accounts of emergent relations, parsimony directs attention to whether new theoretical constructs like emergence or relational frames are necessary to explain the data, or whether existing behavioral concepts like common mediating responses, stimulus generalization, or established conditioning mechanisms are sufficient. BCBAs who apply parsimonious reasoning are better equipped to evaluate new theoretical claims in behavior analysis without either reflexively accepting or rejecting them.
Verbal behavior assessments that include conditional discrimination tasks — such as the VBMAPP milestones related to listener responding and matching — are measuring skills foundational to equivalence class formation. BCBAs who understand equivalence research interpret these assessment data with greater precision: they can identify whether failures reflect deficits in the conditional discrimination itself or in the derived relational responding built upon it, and they can design probes to distinguish between these possibilities. This informs more precise treatment targets and more theoretically grounded programming decisions.
Schlinger's behavioral account of child development situates cognitive, linguistic, and social developmental milestones within the framework of conditioning and learning rather than treating them as the products of maturation or innate structures. This framing has clinical implications: it suggests that the behavioral repertoires associated with development are, in principle, teachable through appropriate learning histories. For BCBAs working with clients who have not acquired typical developmental repertoires, a behavioral account of how those repertoires normally develop provides a roadmap for intervention. Understanding development behaviorally rather than structurally informs both assessment and programming.
Staying current with theoretical developments requires regular engagement with primary literature in JABA, JEAB, and Behavior Analysis: Research and Practice, as well as following researchers whose work addresses foundational theoretical questions. Conference presentations, particularly at the Association for Behavior Analysis International (ABAI), provide exposure to emerging research and debate. Engaging in peer consultation with colleagues who have specialized knowledge in verbal behavior and basic behavioral science deepens theoretical understanding in ways that continuing education alone cannot. BCBAs should treat theoretical literacy as part of their professional competency, not as an academic luxury separate from clinical practice.
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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.