There is a strong empirical and conceptual relationship between language and derived stimulus relations. An empirical relationship does not indicate that derived stimulus relations depend upon language or that such relations are mediated by language. When two dependent variables are correlated, one conservative strategy is to determine whether both variables are reflective of the same basic underlying psychological process. If the two areas do overlap at the level of behavioral process, then questions about human language may also be questions about derived stimulus relations, and vice versa.

This is the basic theoretical and empirical research strategy of RFT. The overarching aim of this behavioral research has been to integrate a range of apparently diverse psychological phenomena including, for example, stimulus equivalence, naming, understanding, analogy, metaphor, and rule-following.

Relational Frame Theory adopts the view that the core defining element in all of these, and many other inherently verbal activities, is arbitrarily applicable relational responding, and moreover that such responding is amenable to a learning or operant analysis.

RFT treats relational responding as a generalized operant, and thus appeals to a history of multiple-exemplar training. Specific types of relational responding, termed relational frames, are defined in terms of the three properties of mutual and combinatorial entailment, and the transformation of functions. Relational frames are arbitrarily applicable, but are typically not necessarily arbitrarily applied in the natural language context.

Mutual entailment refers to the derived bidirectionality of some stimulus relations, and as such it is a generic term for the concept of "symmetry" in stimulus equivalence. "Mutual entailment" applies if stimulus A is related to another stimulus B in a specific context, and as a result a relation between B and A is entailed in that context. Combinatorial entailment refers to instances in which two or more relations that have acquired the property of mutual entailment mutually combine. Combinatorial entailment is the generic term for what is called "transitivity" and "equivalence" in stimulus equivalence. Combinatorial entailment applies when, in a given context, A is related to B and B is related to C, and then in that context a relation is entailed between A and C and another between C and A. For example, if A is bigger than B, and B is bigger than C, then a bigger-than relation is entailed between A and C, and a smaller-than relation is entailed between C and A. A transformation of stimulus functions applies when functions of one event in a relational network is altered based on the functions of another event in the network and the derived relation between them. Mutual and combinatorial entailment are regulated by contextual cues (C rel). The transformation of stimulus functions are regulated by additional contextual cues (C func).

The development of relational responding can be organized into a rough list that gradually becomes more and more complex. We are not presenting this list as a set of stages or steps, and we would expect them to be sequenced only in broad terms and even then only if the training history is typical. Nevertheless, this list gives a sense of the complexity that emerges from the small set of core concepts in Relational Frame Theory.

• Contextually controlled mutual entailment in equivalence

• Contextually controlled combinatorial entailment in equivalence

• Contextually controlled transfer of stimulus functions through equivalence relations

• Integration of these response components into a functional response class: a frame of coordination

• Simple examples of verbal understanding

• Contextually controlled mutual entailment in additional types of stimulus relations

• Contextually controlled combinatorial entailment in additional types of stimulus relations

• Contextually controlled transformation of stimulus functions in additional types of stimulus relations

• Integration of these into additional relational frames

• Simple examples of genuinely verbal governance of behavior by others

• Conditional contextual control over the participation of given elements in relational frames

• The development of relational networks

• More complex examples of verbal understanding

• Verbal governance of the behavior of others (e.g., verbal mands and tacts)

• Transformation of stimulus functions across relational networks

• Increasing number and complexity of relational frames

• Increasing acquisition of specific participants in specific relational frames (e.g., vocabulary)

• Complex interactions between relations (training in one influences development of another)

• Integration of related types of relational frames into families of relational responses

• Elaborated and increasingly subtle contextual control over relational responding (e.g., syntax; number of relational terms)

• Elaborated and increasingly subtle contextual control over transformation of stimulus functions (e.g., number and specificity of functional terms)

• Nonarbitrary properties serve as a relational context for arbitrarily applicable relational responses

• Increasingly complex relational networks

• With acquisition of equivalence, time or causality, and evaluation, the development of relational sentences that function fully as rules

• Relating relational networks

• Transformation of stimulus functions based on the relating of relational networks

• Relating relational networks under the control of nonarbitrary properties of the environment

• More complex examples of rule understanding and rule-governance, particularly pliance and tracking

• Regulation of the behavior of the listener through the establishment of relational networks in the listener

• With the acquisition of hierarchical class membership, use of relational networks to abstract nonarbitrary properties and to have these properties participate in relational frames

• Abstracting properties of the nonarbitrary environment based on relational networks and the relating of relational networks

• With the acquisition of temporal, contingency, and causal relational frames, increased insensitivity to temporal delays

• Development of deictic relational frames

• Development of perspective-taking and sense of self

• Construction of the verbal other

• Construction of the conceptualized group

• Contextual control of relational responding by the nonarbitrary and arbitrary properties of the listener

• Further development of rule-following, particularly augmenting

• Regulation of the behavior of the listener by orienting the listener to abstracted features of the environment

• Acquisition of increasingly abstract verbal consequences

• Self-rule generation and self rule-following

• Pragmatic verbal analysis and increasingly complex forms of problem solving and reasoning

• Increasing dominance of the verbal functions of the environment

The foregoing provides a summary of the key features of RFT. The key concept that underlies Relational Frame Theory is extremely simple—try to think of relating per se as learned behavior. As the list above shows, however, applying this simple idea leads to many specific points—the nature of an arbitrarily applicable relational response, the role of context, the varieties of relational responses, the role of the nonarbitrary environment, networks of relations, the use of these abilities to solve problems, the development of self, and so on.

Advantages of the RFT Approach to Human Language and Cognition

There are many different theories—in many different disciplines—that attempt to explain or account for human language and cognition. With so many different theories available, what is unique or special about Relational Frame Theory?

We believe the functional, contextualistic approach of RFT to understanding complex human behavior has led to a system of analysis that offers many advantages over the traditional structural and “information transmission” models of language and cognition (Blackledge, 2003). These advantages include:

• RFT is parsimonious, relying on relatively few basic principles and concepts to account for language and cognition.

• RFT is precise, allowing the study of human language to be conducted in accordance with the carefully-specified definitions of its component processes.

• RFT has broad scope, providing plausible explanations and new empirical approaches to a wide variety of complex human behaviors in both basic and applied domains (such as problem solving, metaphors, self, spirituality, values, rule-governed behavior, psychopathology, intelligence, etc.).

• RFT has depth, meaning that its analyses cohere with established treatments at other levels of analysis. For example, it provides plausible accounts of cultural phenomena such as knowledge amplification; recent neurological research indicates that the brain processes seen while subjects engage in derived relational responding fit with the RFT language claim; and connectionist models of the learning history needed to establish relational frames coheres with RFT.

• The principles of RFT are directly observable, especially under laboratory conditions, so no tenuous inferences about the existence of unseen structures or processes (such as cognitive schemas or language acquisition devices) are required.

• RFT is firmly based on empirical research that has without exception supported its tenets. In addition to the over 30 published empirical treatments of RFT, the theory also accounts for the data observed in hundreds of empirical studies on the concept of stimulus equivalence that have been published since 1971. RFT has withstood all empirical tests so far, and all of its core claims now have at least some supportive data. So far, no data has arisen in contradiction to the theory.

• RFT has direct applied and clinical applications that are not apparent in other accounts of human language and cognition. There are many successful empirical studies on applied methods based on RFT (particularly Acceptance and Commitment Therapy, but including other methods as well, such as methods of attitude change, or the treatment of stigma and prejudice, or increasing intelligence) and many clear applied implications yet to be pursued.

• RFT is generative. The account leads quickly to innovative and (so far) empirically successful approaches to virtually all of the important topics in the language and cognition domain.

• RFT is testable. Its core claim (that relating can be thought of as learned, operant behavior) is an empirical matter. If relational frames do not develop, come under contextual control, respond to shaping via multiple exemplar training, and respond to consequences, then the theory is false. Further, its claim that relational frames are the core of human language is testable both directly and pragmatically. For example, if RFT does not lead to more successful education interventions than those that currently exist, then it fails. (see section on research evidence).

• RFT is progressive. RFT supports what is within the "protective belt" of the behavioral paradigm and yet is generative in the sense described above (see Lakatos for this approach to progressivity). RFT is a behavioral theory that builds on everything that is known about basic behavioral principles, but takes this basic account into a fundamentally new direction with profound and exciting implications for almost every topic relating to complex human behavior. Yet it does so without any patchwork corrections to the basic assumptions of the behavioral paradigm. This has resulted in newer models that are being updated as well as changes in methodology to study topics of interest more precisely.

• RFT is coherent. Its philosophical basis is well articulated; its assumptions are clearly stated; its concepts are carefully defined; and all of these levels fit together.