Precis of Semantic Cognition: A Parallel Distributed Processing Approach

In this precis of our recent book, Semantic Cognition: A Parallel Distributed Processing Approach (Rogers & McClelland 2004), we present a parallel distributed processing theory of the acquisition, representation, and use of human semantic knowledge. The theory proposes that semantic abilities arise from the flow of activation among simple, processing, neuron-like processing units, as goverend by the strengths of interconnecting weights; and that acqusition of new semantic information involves the gradual adjustment of weights in the system in response to experience. These simple ideas explain a wide range of empirical phenomena from studies of categorization, lexical acquisition, and disordered semantic cognition. In this precis we focus on phenomena central to the reaction against similarity-based theories that arose in the 1980s and that subsequently motivated the theory-theory approach to semantic knowledge. Specifically, we consider (1) how concepts differentiate in early development, (2) why some groupings of items seem to form good or coherent categories while others do not, (3) why different properties seem central or important to different concepts. (4) why children and adults sometimes attest to beliefs that seem to contradict their direct experience. (5) how concepts reorganize between the ages of 4 and 10, and (6) the relationship between causal knowledge and semantic knowledge. The explanations our for these phenomena are illustrated with reference to a sample feed-forward connectionist model. The relationships between this simple model, the broader theory, and more general issues in cognitive science are discussed.