By the 1890s, psychology was accepted as a scientific subject separate from its philosophical origins. Laboratories and university departments had been established in Europe and the USA, and a second generation of psychologists was emerging. In the USA, psychologists anxious to put the new discipline on an objective, scientific footing reacted against the introspective(自省的), philosophical approach taken by William James and others.
Introspection, they felt, was by definition subjective, and theories based on it could be neither proved nor disproved(反驳); if psychology was to be treated as a science, it would have to be based on observable and measurable phenomena. Their solution was to study the manifestation of the workings of the mind – behaviour – under strictly controlled laboratory conditions. As John B. Watson put it, psychology is “that division of Natural Science which takes human behaviour – the doings and sayings, both learned and unlearned – as its subject matter”.
Early “behaviourists”, including Edward Thorndike, Edward Tolman, and Edwin Guthrie, designed experiments to observe the behaviour of animals in carefully devised situations, and from these tests inferred theories about how humans interact with their environment, as well as about learning, memory, and conditioning.
Behaviourist experiments were influenced by similar experiments devised by physiologists studying physical processes, and it was a Russian physiologist, Ivan Pavlov, who unwittingly(无意地) provided a basis for the emergent behaviourist psychology. In his now famous study of salivation(分泌唾液) in dogs, Pavlov described how an animal responds to a stimulus in the process of conditioning, and gave psychologists the foundation on which to build the central idea of behaviourism.
The notion of conditioning, often referred to as “stimulus–response” (S–R) psychology, shaped the form behaviourism was to take. The behaviourist approach concentrated on observing responses to external stimuli, ignoring inner mental states and processes, which were thought to be impossible to examine scientifically and therefore could not be included in any analysis of behaviour.
The shift from “mind” to “behaviour” as a basis for the study of psychology was revolutionary, and was even accompanied by a “behaviourist manifesto” – the paper Psychology as the Behaviorist Views It, delivered in 1913 by Watson. In the USA, which was leading the field in psychology, behaviourism became the dominant approach for the next 40 years. Evolving from the idea of Pavlovian or classical conditioning came Watson’s assertion that environmental stimuli alone shape behaviour; innate or inherited factors are not involved.
The next generation included the “radical behaviourist” B.F. Skinner, who proposed a rethink of the stimulus–response notion in his theory of “operant(操作的) conditioning” – which stated that behaviour was shaped by consequences, not by a preceding stimulus. Although the concept was similar to ideas proposed by William James, it radically altered the course of behaviourism, taking into account genetic factors and explaining mental states as a result (rather than as a cause) of behaviour.
The cognitive revolution
By the mid-20th century, however, psychologists were questioning the behaviourist approach. Ethology, the study of animal behaviour, showed the importance of instinctive as well as learned behaviour – a finding that sat uncomfortably with strict ideas of conditioning. A reaction to Skinner’s ideas also sparked the “cognitive revolution”, which turned attention once again from behaviour back to the mind and mental processes.
A key figure at this time was Edward Tolman, a behaviourist whose theories had not dismissed the importance of perception and cognition, due to his interest in German-based Gestalt psychology. Advances in neuroscience(神经科学), explored by another behaviourist, Karl Lashley, also played a part in shifting the emphasis from behaviour to the brain and its workings. Behaviourism had now run its course, and was superseded(替代) by the various branches of cognitive psychology.
However, its legacy, particularly in establishing a scientific methodology for the subject, and in providing models that could be used in psychological experimentation, was a lasting one. Behavioural therapy is also still in use today, as an essential part of cognitive-behavioural therapy.