[From English behavior: the manner in which a person, animal, or thing acts, either characteristically or in particular circumstances.]
(psychology) The doctrine that only a person's or animal's externally observed ways of acting provide legitimate data for the study of psychology. As originally formulated by John D. Watson in 1913, behaviorism was a methodological principle defined in order to pursue scientific objectivity in psychology. However, the behaviorist movement - pushed forward by prominent psychologists such as B.F. Skinner (1904-1990) and influenced by scientific operationalism - soon came to dismiss any internal states, mental phenomena, or higher-order emergent properties of living beings. The result was a kind of reductionism, materialism, or even automatism applied to animal and human activity, which in its more radical forms did not even seek to reduce consciousness to stimulus-response interactions, but simply ignored mental phenomena altogether. Since the 1960s, behaviorism has been supplanted by psychological cognitivism and more recently by evolutionary psychology and other trends.