In psychology behaviourism, associated with Watson and such researchers as Ivan Pavlov (1849–1936), was first of all a methodological view, counselling the avoidance of introspection and the subjective in favour of the scientific measurement of behaviour and its causes. In later hands, particularly those of B. F. Skinner (1904–1990), the view became identified with a simplistic vision of the springs of human action, and with the prospect of control of action by relatively simple manipulation of the stimuli and patterns of reinforcement that are allowed to impinge on an agent. Skinner's belief that the explanation of behaviour through belief, intention, and desire is somehow unscientific, or the preserve of ‘mentalists’, has also lost ground to the development of cognitive studies.

Philosophically the doctrine of behaviourism is that mental states are logical constructions out of dispositions to behaviour, or in other words, that describing the mental aspects of a person is a shorthand for describing the various dispositions to behaviour that the person possesses. The most influential work promoting this point of view was The Concept of Mind (1949) by Ryle which urged behaviourism as the best defence against the Cartesian myth of the ‘ghost in the machine’. The extent to which Wittgenstein, writing the Philosophical Investigations at the same time, intended to promote a behaviourist doctrine is subject to dispute. Like other reductionist doctrines behaviourism fell foul of the difficulty of providing workable analyses, notably because of the holism of the mental, or the fact that how a person behaves is not a function of one belief or one desire, but of a whole field or network of beliefs and desires. The modification to take care of this turns behaviourism into its more popular modern successor, functionalism.