Cognition, Learning and Memory: A Parallel Distributed Processing Approach

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This project will consider two topics that arise in the development of a theoretical framework, known as the parallel distributed processing (PDP) framework, for understanding learning, memory, and cognitive processes. In this framework, cognitive processes emerge from the simultaneous activity of a large number of simple processing units; the knowledge that governs processing is represented by the numerical strengths of connections among the units. The approach will be applied to recall of information from memory and to language acquisition. From a PDP perspective, recall becomes a process of constructing the representation of a to-be-remembered item from the contributions of a number of prior experiences. This view predicts that information acquired at different times may be combined in the same act of recall, producing "blend" errors in memory. The first part of the project will verify that such errors occur and will examine the circumstances under which they occur. The experiments will examine the effects of similarity of memory traces, will assess the tendency for blend errors to occur in recognition as well as recall, and will determine whether blend errors occur more frequently when the different experiences to be combined complement, rather than conflict, with each other. These experiments will help clarify when and how the mechanisms of memory can give rise to errors that could invalidate eyewitness testimony. From a PDP perspective, learning language is not a matter of learning a system of linguistic rules per se; rather, it is a matter of adjusting connection strengths among units. The second part of the project will examine whether this view is consistent with children's acquisition of one aspect of language, namely the use of inflected forms of verbs (e.g., the past tense). This part of the project will attempt to develop a revision of an earlier model of acquisition by connection strength adjustment and to use the model to account for errors that children make during acquisition. This part of the project should help clarify the nature of the mechanisms that underlie the acquisition of language.