Connectionism and developmental theory

The main goal of this paper is to argue for an ‘epigenetic developmental interpretation’ of connectionist modelling of human cognitive processes, and to propose that Parallel Distributed Processing (PDP) models provide a superior account of developmental phenomena than that offered by cognitivist (symbolic) computational theories. After comparing some of the general characteristics of epigeneticist and cognitivist theories, we provide a brief overview of the operating principles underlying Artificial Neural Networks (ANNs) and their associated learning procedures. Four applications of different PDP architectures to developmental phenomena are described. First, we assess the current status of the debate between symbolic and connectionist accounts of the process of English past tense formation. Second, we introduce a connectionist model of concept formation and vocabulary growth and show how it provides an account of aspects of semantic development in early childhood. Next, we take up the problem of compositionality and structure dependency in connectionist nets, and demonstrate that PDP models can be architecturally designed to capture the structural principals characteristic of human cognition. Finally, we review a connectionist model of cognitive develop ment which yields stage‐like behavioural properties even though architectural and input assumptions remain constant throughout training. It is shown how the organizational characteristics of the model provide a simple but precise account of the equilibration of the processes of accommodation and assimilation. The article concludes that a coherent epigcnctic‐developmental interpretation of PDP modelling rquires the rejection of so‐called hybrid‐architecture theories of human cognition.