After years of behaviorist denial of mental terms, DONALD HEBB (1949) admonished: "We all know that attention and set exist, so we had better get the skeleton out of the closet and see what can be done with it." Donald E. Broadbent (1926-1993), more than anyone, deserves the credit for shedding scientific light on this "skeleton." Through his own empirical contributions and his careful analyses of the findings of others, Broadbent demonstrated that experimental psychology could reveal the nature of cognitive processes. In his hands, an information processing approach to understanding ATTENTION, perception, MEMORY, and performance was exceptionally illuminating, and helped initiate and fuel the paradigm shift known as the "cognitive revolution."
Broadbent joined the Royal Air Force in 1944. Noting equipment poorly matched to the human pilot, the importance of practice, and the possibility of measuring individual differences, he envisaged a career in psychology. Under the leadership of Sir Frederic BARTLETT, the Psychology Department at Cambridge University was engaged in solving precisely the kind of real world problems that excited Broadbent. Upon graduation in 1949, Broadbent went straight into research as a staff member at the Medical Research Council's Applied Psychology Unit (APU) in Cambridge.
Broadbent's early research and thinking were strongly influenced by the APU's first two directors, Bartlett and Kenneth Craik. Bartlett (1932) emphasized that people were active, constructivist processors; Craik (1943) pioneered the use of engineering concepts (cybernetics) to explain human performance. At the time, communication theory (Shannon 1948), with its information metric and concept of a communication channel with a limited capacity for information transmission, was being applied to psychological phenomena. Broadbent induced the key principles of his "filter" theory from three basic findings on selective listening (e.g., Cherry 1953): (1) People are strictly limited in their ability to deal with multiple messages (sources of sensory information); (2) the ability to focus on one message while ignoring another, irrelevant one is greatly improved if the messages differ in a simple physical property such as location or pitch; and, (3) the consequence of focusing on one message is that the content of the ignored message is unreportable (though simple physical properties can be picked up).
These and other findings, and the theoretical framework Broadbent induced from them, were described in his first major work, Perception and Communication (1958). The information processing architecture of Broadbent's famous filter theory (fig. 1) quickly became the most influential model of human cognitive activity cast in information processing terms. Thirteen years later, when Broadbent published his second major work, Decision and Stress (1971), it was shown how the 1958 model needed modification: new mechanisms for selection (pigeon-holing and categorizing) that operated later in the processing sequence were added to filtering and an emphasis on the statistical nature of evidence accumulation and decision making was incorporated.
Figure 1. Broadbent's (1958) filter theory asserts that there exists a limited capacity stage of perception (P-system), that this stage is preceded by parallel analysis of simple stimulus features, and that access to the P-system is controlled by a selective filter. Short-term and long-term (store of conditional probabilities of past events) memory systems were postulated and integrated into the information processing system. (This figure is modeled on Broadbent 1958: 297.)
In light of their growing popularity it might be suggested that artificial NEURAL NETWORK models will replace the information processing approach. While acknowledging the value of models cashed out in neural network terms, Broadbent (1985) points out (cf. MARR 1982) that such models are at a different level of analysis (implementation) than information processing models (computation); the appropriate level depends on the nature of the problem to be solved. Considering the problem of designing human-machine systems for data-rich environments, Moray suggests an enduring role for models like Broadbent's: "Whatever the deep structure of attention may be, its surface performance is, in the vast majority of cases, well described by a single, limited capacity channel, which is switched discretely among the various inputs" (1993: 113).
Donald Broadbent was attracted to psychology because he believed that the application of psychological principles could benefit people. It is fitting, then, that in 1958 he was selected to direct the APU, which he did for sixteen years. During this time the APU -- already widely respected -- would become one of the world's preeminent facilities for pure and applied psychological research. After this period of steadfast administrative service, Broadbent -- who never held an academic appointment -- stayed on the Medical Research Council's scientific staff while moving to Oxford. Although Broadbent is, and will continue to be, best known for his empirical and theoretical work on attention, his endorsement of applied psychology never waned. Thus, in contrast to an emphasis on the cognitive "hardware" implicit in his filter theory, Broadbent's belief in the importance of cognitive "software" (task variables and individual differences in strategy selection), led him to predict: "In the long run, psychology will, like computer science, become an ever-expanding exploration of the merits and disadvantages of alternative cognitive strategies" (1980: 69).
Broadbent (1980) was genuinely ambivalent about what he called "academic psychology," and although he recognized the importance of theory, unlike many of his contemporaries, he rejected the hypothetico-deductive approach as inefficient, advocating instead experiments whose results could discriminate between classes of theory (1958: 306) and generate a solid, empirical foundation (Broadbent 1973). In light of these attitudes, it is somewhat ironic that Broadbent would have such a great impact on academic psychology (wherein his theoretical language helped foster the cognitive revolution) and that his theory of attention would become the benchmark against which all subsequent theories are compared.
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Broadbent, D. E. (1958). Perception and Communication. Oxford: Pergamon.
Broadbent, D. E. (1971). Decision and Stress. London: Academic Press.
Broadbent, D. E. (1973). In Defense of Empirical Psychology. London: Methuen.
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Broadbent, D. E. (1985). A question of levels: comment on McClelland and Rumelhart. Journal of Experimental Psychology: General 114:189-192.
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Broadbent, D. E. (1977). Levels, hierarchies and the locus of control. Quarterly Journal of Experimental Psychology 32:109-118.
Duncan, J. (1996). Information and uncertainty in a cumulative science of behavior: 25 years after Broadbent's Decision and Stress. American Journal of Psychology 109:617-625.
Klein, R. M. (1996). Attention: yesterday, today and tomorrow. Review of Attention: Selection, Awareness and Control -- A Tribute to Donald Broadbent. American Journal of Psychology 109:139-150.
Posner, M. I. (1972). After the revolution . . . What? Review of Decision and Stress. Contemporary Psychology 17:185-187.
Posner, M. I. (1987). Forward. In D. E. Broadbent, Perception and Communication. Oxford University Press, pp. v - xi .
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