Relational frame theory (RFT) is a behavior analytic theory of human language, cognition, and behaviour developed by Steven C. Hayes. RFT is rooted in functional contextualism, and argues that the building block of human language and higher cognition is relating, i.e. the human ability to create bidirectional links between things. Relational frame theory focuses on how humans learn language (i.e., communication) through interactions with the environment.

RFT is a behavioral theory of language and higher cognition. rooted in functional contextualism.

In his 1957 book Verbal Behavior, B.F. Skinner presented an interpretation of language. However, this account was intended to be an interpretation as opposed to an experimental research program, and researchers commonly acknowledge that the research products are somewhat limited in scope. For example, Skinner's behavioral interpretation of language has been useful in some aspects of language training in developmentally disabled children, but it has not led to a robust research program in the range of areas relevant to language and cognition, such as problem-solving, reasoning, metaphor, logic, and so on. RFT advocates are fairly bold in stating that their goal is an experimental behavioral research program in all such areas, and RFT research has indeed emerged in a large number of these areas, including grammar.

In a review of Skinner's book, linguist Noam Chomsky argued that the generativity of language shows that it cannot simply be learned, that there must be some innate "language acquisition device". Many have seen this review as a turning point, when cognitivism took the place of behaviorism as the mainstream in psychology. Behavior analysts generally viewed the criticism as somewhat off point. However, it is undeniable that psychology turned its attention elsewhere, and the review was very influential in helping to produce the rise of cognitive psychology.

Despite the lack of attention from the mainstream, behavior analysis is alive and growing. Its application has been extended to areas such as language and cognitive training. Behavior analysis has long been extended as well to animal training, business and school settings, as well as hospitals and areas of research.

RFT was originally developed by Steven C. Hayes of University of Nevada, Reno and has been extended in research, notably by Dermot Barnes-Holmes and colleagues of Ghent University.

RFT distinguishes itself from Skinner's work by identifying and defining a particular type of operant conditioning known as arbitrarily applicable derived relational responding (AADRR). In essence, the theory argues that language is not associative but is learned and relational. For example, young children learn relations of coordination between names and objects; followed by relations of difference, opposition, before and after, and so on. These are "frames" in the sense that once relating of that kind is learned, any event can be related in that way mutually and in combination with other relations, given a cue to do so. This is a learning process that to date appears to occur only in humans possessing a capacity for language: to date relational framing has not yet been shown unambiguously in non-human animals despite many attempts to do so. AADRR is theorized to be a pervasive influence on almost all aspects of human behavior. The theory represents an attempt to provide a more empirically progressive account of complex human behavior while preserving the naturalistic approach of behavior analysis.

Relational frame theory argues that the building block of human language and higher cognition is relating, i.e. the human ability to create bidirectional links between things. It can be contrasted with associative learning, which discusses how animals form links between stimuli in the form of the strength of associations in memory. RFT argues that natural human language typically specifies not just the strength of a link between stimuli but also the type of relation as well as the dimension along which they are to be related. For example, a tennis ball could be associated with an orange, by virtue of having the same shape, but it is different because it is not edible, and is perhaps a different color. In the preceding sentence, 'same', 'different' and 'not' are cues in the environment that specify the type of relation between the stimuli, and 'shape', 'colour' and 'edible' specify the dimension along which each relation is to be made. Relational frame theory argues that while there is an arbitrary number of types of relations and number of dimensions along which stimuli can be related, the core unit of relating is an essential building block for much of what is commonly referred to as human language or higher cognition.