Associationism: Not the Cliff Over Which To Push Connectionism RENE J. JORNA and WILLEM F G. HASELAGER Management Informatics, University of Groningen, Groningen, The Netherlands and Department of Psychology, Free University Amsterdam Amsterdam, The Netherlands CONTENTS Page Synopsis 279 1. Introduction 280 2. Associationism: a conceptual structure 284 2.1 Couples and couple signs 286 2.2 The nature of the relationship 288 2.3 Two couple elements 290 2.4 Similarity and contiguity 291 2.5 Recursive associations 297 3. Conclusions concerning the analysis and interpretation of association 300 Acknowledgements 304 References 305 SYNOPSIS In the present discussion in artificial intelligence and intelligent architectures several authors have come to the conclusion that the overall domination of classical cognitive science has gone. One of the arguments 279 Volume 4. Nos. 3-4, 1994 Associationism: Not the Cliff Over Which to Push Connectionism in this discussion concerns the interpretation and status of the notion of association. Cognitive scientists equated association with behaviorism and because of the downfall of behaviorism they rejected the history of associationism. Opponents of symbolic A.I., especially connectionists, favoured associationism as necessary in explaining learning and reasoning. In this article we consider the notion of association to be ambivalent. In order to clear the ground we treat associationism as a conceptual structure consisting of five main principles, dealing with the interpretation of (couple) elements (judgements, ideas, stimuli, neurons, symbols, etc.) and the systematicity in the construction of elements and relations. On the basis of these principles historical material will be reviewed. We conclude that associationism should not be used as a simplistic label (positive or negative) in the debate between classical cognitivists and connectionists. 1. INTRODUCTION In the present discussion in artificial intelligence and intelligent architectures several authors have come to the conclusion that the overall domination of classical cognitive science has gone (Ramsey, Stich & Rumelhart, 1991; Bechtel & Abrahamsen, 1991). The most extreme position holds that cognitive science started in 1956 (Gardner, 1985) and stopped to be interesting in 1986 with the publication of the book on Parallel Distributed Processing (McClelland, Rumelhart & the PDP-Group, 1986). This does not imply that PDP or connectionist models do not study cognition. Their theoretical background, however, is different from the approach of classical cognitive science. In the extreme it is stated by some connectionists that future research on cognitive modelling can only be fruitful within a PDP or connectionist mode. This claim is a very strong one and in several articles it has been defended (Bechtel, 1985; Smolensky, 1988) and attacked (Fodor & Pylyshyn, 1988; Levelt, 1989). One of the arguments in this discussion concerns the interpretation and status of the notion of association. The problem with this notion and its implications for cognition is that its relevance is interpreted into two opposite directions. 280 R.J. Joma and W.F.G. Haselager Journal of Intelligent Systems The first direction is developed by Levelt (1989) who claims that connectionism has to be rejected, because this endeavour is just a new version of the old doctrine of association, called, associationism. In this he follows Fodor & Pylyshyn who say amongst others: "the idea that the brain is a neural network motivates the revival of a largely discredited Associationist psychology." (1988, p. 63). In the history of psychology, behaviorism is a version of associationism. In the 1950s cognitive science succeeded in defeating behaviorism. One of the weak points in behaviorism is that it rests on the notion of association. Connectionism as a new research area in the mind-and-brain sciences also rests on the notion of association. Because cognitive science already showed the untenability of behaviorism that is based on the notion of association as fundamental for research on mind-and-brain, connectionism rests on a mistake. A similar negative evaluation of associationism with respect to neurophysiological theories can be found in Buckingham (1984), who considers associationism as a price to pay for a 'cerebral connectionistic' approach. The second, opposite, direction is worked out by Bechtel (1985). He claims that cognitive science does not take into account learning. According to him one of the reasons for this omission is the neglect of the important role of association. Because intelligence is based among other things upon association and because the only true follow-up of associationism is to be found in connectionist networks, the high-days of classical cognitive science are over. There is no cognition without association. In our opinion Bechtel is right with this last statement but for reasons different from the ones he offers. Both opposite perspectives emphasize the role of association. This is done, however, without giving a detailed characterization of this notion. In this article our goal is twofold. First of all we will give a rather detailed analysis of historical, 'classical' associationism. We think associationism is a rather complex conceptual structure, not just a simplistic label. In the second place we will use this analysis to assess the value of associationism in the evaluation of connectionism as a modelling approach to the mind. 281 Volume 4, Nos. 3-4, 1994 Associationism: Not the Cliff Over Which to Push Connectionism We hope to show that associationism should not be seen as a 'mistake' of which connectionism is to be accused. Several attempts have been made to incorporate the history of associationism in (cognitive) psychological research (Robinson, 1932; Deese, 1966). Besides the comments of Bechtel, Fodor & Pylyshyn and Levelt a recent and influential one is from Anderson & Bower (1973). They tried to link their Human Associative Memory (HAM) model to the history of (classical) associationism. They argue that associationism does not represent a specific position, but only a theoretical tradition. According to Anderson & Bower this tradition is characterized by four features, namely associationism is connectionistic, it is reductionistic, it is sensationalistic and it is mechanistic. The problem with this description is that the characterization is not quite satisfactory. We will discuss the four features in brief. The connectionistic feature implies that "ideas, sense data or similar mental elements are associated together in the mind through experience. This means that it is connectionistic" (Anderson & Bower, 1973, p. 10). The essence of associationism is of course that connections are made. If this definition is used, nearly all (cognitive) psychology is connectionistic. The important point, of course, is how and why connections arise. The history of associationism and present day psychology show that different answers have been given to these questions. The second feature says that associationism is reductionistic, which means that "ideas can ultimately be decomposed into a basic stock of 'simple ideas'" (Anderson & Bower, p. 10). This feature is rather ambiguous. Reductionist might refer to decomposition and to composition. Warren (1921) shows that many associationists, for example John Stuart Mill, Tucker, and Brown, start with simple elements that can be combined into complex ones, but it is also argued that sometimes the decomposition from complex ideas to simple ones is not possible, because the complex ones show characteristics that cannot be reduced to the simple ones. It is, 282 R.J. Jorna and W.F.G. Haselager Journal of Intelligent Systems therefore, not precisely to the point to conclude that reductionism is a defining feature of associationism. A feature of associationism is that it studies compounds or composites. The research question in this case is by what regularities and under what preconditions compounds are likely to occur. According to Anderson & Bower (1973, p. 10): "The simple ideas are to be identified with elementary, unstructured sensations. [...] Because it identifies the basic components of the mind with sensory experience, associationism is sensationalistic." This feature is questionable. It seems to mean that those philosophers and psychologists who only study the connections and combinations of the mind and leave perception and sensation outside the discussion are not associationists. However, it is one issue to study the relation between elements in perception and elements in cognition, but it is another issue to study the train of thought, reasoning and memory as such. One does not necessarily have to be an empiricist, not in philosophy nor in psychology, to be an investigator of the mind in the associationistic tradition. The last feature of associationism implies that "simple, additive rules serve to predict the properties of complex associative configurations from the properties of underlying simple ideas." (Anderson & Bower, 1973, p. 10). According to Anderson & Bower associationism is mechanistic (i.e., non-intentional). Thinking, reasoning and memory processes are only to be conceived in mechanical terms. However, it is not self-evident that the elements in the association process are all like the bricks that constitute a house or the particles such as described in classical mechanics (which heavily influenced British associationism) to be connected in a simple, straightforward way. Ideas, concepts