Functional contextualism
Functional contextualism is an extension and contextualistic interpretation of B.F. Skinner's radical behaviorism rooted in philosophical pragmatism and contextualism. It considers behavior as "acts in context", inseparable from its current and historical context. The truth criterion of contextualism is "successful working": acts (behavior and thoughts) are true or 'truth' or valid when they lead to effective action, or achievement of some goal. Functional contextualism was first delineated by Steven C. Hayes, and serves as the basis of his theory of language known as relational frame theory and his acceptance and commitment therapy.