• How do humans and animals think and act?
The origins of scientific psychology are usually traced to the work of the German physicist Hermann von Helmholtz (1821–1894) and his student Wilhelm Wundt (1832–1920). Helmholtz applied the scientific method to the study of human vision, and his Handbook of Physiological Optics is even now described as “the single most important treatise on the physics and physiology of human vision” (Nalwa, 1993, p.15). In 1879, Wundt opened the first laboratory of experimental psychology, at the University of Leipzig. Wundt insisted on carefully controlled experiments in which his workers would perform a perceptual or associative task while introspecting on their thought processes. The careful controls went a long way toward making psychology a science, but the subjective nature of the data made it unlikely that an experimenter would ever disconfirm his or her own theories. Biologists studying animal behavior, on the other hand, lacked introspective data and developed an objectivemethodology, asdescribed byH.S.Jennings (1906) inhisinfluential work Behaviorof the Lower Organisms. Applying this viewpoint to humans, the behaviorism movement, led by John Watson (1878–1958), rejected any theory involving mental processes on the grounds that introspection could not provide reliable evidence. Behaviorists insisted on studying only objective measures of the percepts (or stimulus) given to an animal and its resulting actions (or response). Behaviorism discovered a lot about rats and pigeons but had less success at understanding humans. Cognitive psychology, which views the brain as an information-processing device,can be traced back at least to the works of William James (1842–1910). Helmholtz also insisted that perception involved a form of unconscious logical inference. The cognitive viewpoint was largely eclipsed by behaviorism in the United States, but at Cambridge’s Applied Psychology Unit, directed by Frederic Bartlett (1886–1969), cognitive modeling was able to flourish. The Nature of Explanation, by Bartlett’s student and successor Kenneth Craik (1943), forcefully reestablished the legitimacy of such “mental” terms as beliefs and goals, arguing that they are just as scientific as, say, using pressure and temperature to talk about gases, despite their being made of molecules that have neither. Craik specified the three key steps of a knowledge-based agent: (1) the stimulus must be translated into an internal representation, (2) the representation is manipulated by cognitive processes to derive new internal representations, and (3) these are in turn retranslated back into action. He clearly explained why this was a good design for an agent:
If the organism carries a “small-scale model” of external reality and of its own possible actionswithin its head,it is able to tryout variousalternatives,concludewhichis the best of them, react to future situations before they arise, utilize the knowledge of past events in dealing with the present and future, and in every way to react in a much fuller, safer, and more competentmannerto the emergencies which face it. (Craik, 1943)
After Craik’s death in a bicycle accident in 1945, his work was continued by Donald Broadbent, whose book Perception and Communication (1958) was one of the first works to model psychological phenomena as information processing. Meanwhile, in the United States, the development of computer modeling led to the creation of the field of cognitive science. The field can be said to have started at a workshop in September 1956 at MIT. (We shall see that this is just two months after the conference at which AI itself was “born.”) At the workshop, George Miller presented The Magic Number Seven, Noam Chomsky presented Three Models of Language, and Allen Newell and Herbert Simon presented The Logic Theory Machine. These three influential papers showed how computer models could be used to address the psychology of memory, language, and logical thinking, respectively. It is now a common (although far from universal) view among psychologists that “a cognitive theory should be like acomputer program” (Anderson, 1980); thatis, itshould describe adetailed informationprocessing mechanism whereby some cognitive function might be implemented.
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