The Computational Metaphor and Cognitive Psychology

The past three decades have witnessed a remarkable growth of research interest in the mind. This trend has been acclaimed as the ‘cognitive revolution’ in psychology. At the heart of this revolution lies the claim that the mind is a computational system. The purpose of this paper is both to elucidate this claim and to evaluate its implications for cognitive psychology. The nature and scope of cognitive psychology and cognitive science are outlined, the principal assumptions underlying the information processing approach to cognition are summarised and the nature of artificial intelligence and its relationship to cognitive science are explored. The ‘computational metaphor’ of mind is examined and both the theoretical and methodological issues which it raises for cognitive psychology are considered. Finally, the nature and significance of ‘connectionism’—the latest paradigm in cognitive science—are briefly reviewed. Introduction The remarkable upsurge of research interest in cognition has been acclaimed as a revolution in twentieth-century psychology (Baars, 1986; Gardner, 1985; Matlin, 1989). This revolution was hastened by three developments between 1940 and 1960 (Lachman et al., 1979). Firstly, it was shown that Behaviourism, the dominant paradigm in that era, was unable to explain how people understand and acquire language (Chomsky, 1959). Secondly, the development of Communication Theory (Shannon & Weaver, 1949) provided a method of measuring the amount of information flowing through a given system. Thirdly, the advent of digital computers offered psychologists both a plausible metaphor (i.e., the mind as a computational system) and a new method (i.e., computer simulation) for the investigation of the mind. In this paper, we focus on the third of these developments. Our intention is to examine the principal psychological issues raised by the view that the mind is a computational system, what Boden (1979) called the ‘computational metaphor’. We begin by sketching the nature of cognitive psychology and its interdisciplinary ally, cognitive science. We then outline the assumptions underlying the information processing paradigm in contemporary cognitive psychology. This is followed by an analysis of the nature of Artificial Intelligence (AI) and its relationship to cognitive science. We then articulate the computational metaphor and critically explore some significant issues which it raises for cognitive psychology. Finally, we examine Connectionism, (McClelland et al.. 1986; Rumelhart et al., 1986), the ‘new wave’ in cognitive science, and compare and contrast it with Classical Computationalism (Palmer, 1987). Cognitive psychology and cognitive science Cognitive psychology is the modern discipline which tries to elicit empirical answers to the venerable question of how the mind works. It is concerned with the acquisition, representation and use of human knowledge and it investigates the mental processes “by which the sensory input is transformed, reduced, elaborated, stored, recovered and used” (Neisser, 1967, pp. 4-5). According to Neisser, whose textbook is the seminal work in this field, “the task of ... trying to understand human cognition is analogous to that of ... trying to understand how a computer has been programmed” (p.6). This analogy is cho-