The theory according to which mental states can be analyzed in terms of observable behavior or dispositions to engage in such behavior.

Behaviorism is now widely, but not universally believed to have been discredited. The recent work of some researchers who focus on the dynamic, interactive, situated behavior of cognitive systems have been re-exploring ideas central to behaviorism. Historically, behaviorism had two mains forms:
Methodological behaviorists (also called `psychological behaviorists') claim that the proper domain of psychology is the study of behavior. Appeals to unobservable inner states are both methodologically intractable (e.g. the inconsistent first person reports of introspectionists), and unnecessary (we can control and predict behavior by appeal to external variables that systematically induce behavioral responses as a consequence of conditioning or reinforcement histories). This position was spearheaded by J. B. Watson and most influentially defended by his student, B. F. Skinner. Sometimes methodological behaviorists express agnosticism about the existence of inner mental states, and sometimes they express skepticism, comparing such states to phlogiston, caloric acid, and other posits of discredited theories. Methodological behaviorism dominated American psychology between 1913, when Watson wrote his seminal defense, and 1957, when Chomsky published a devastating review of Skinner's behavioral analysis of language.
In its strongest form, philosophical behaviorism (also called `analytic behaviorism' and `logical behaviorism') is the view that psychological terms can be translated without loss of meaning into behavioral terms. Weakened versions replace translatability with weaker forms of semantic correlation (e.g., co-extensionality), and include neural and other physical terms among those in terms of which mental states can be characterized. Philosophical behaviorism is associated with the Logical Positivists (most notably, Hempel), who endorsed the verifiability principle, according to which the meaning of a term is given by its conditions of verification. Since statements ascribing mental predicates are verified by observing behavior, behavioral tests enter into the meanings of those mental predicates. A similar position was influentially defended by Ryle. Some subsequent critics of logical positivism continued to endorse their semantically motivated skepticism about inner mental states and their preoccupation with observable behavior (e.g., Quine and Wittgenstein), but such skepticism waned considerably with the rise of the psychophysical identity theory and functionalism in the 1950s and '60s.
Jesse Prinz