Botvinick, M., and Plaut, D. C. (2000). Doing without schema hierarchies: A connectionist approach to routine sequential action and its pathologies [Abstract]. Cognitive Neuroscience Society Annual Meeting Abstract Program (supplement of the Journal of Cognitive Neuroscience).
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Abstract: In everyday tasks, selecting actions in the proper sequence requires a continuously updated representation of temporal context. Many existing models address this problem by positing a hierarchy of processing units, mirroring the roughly hierarchical structure of naturalistic tasks themselves. Such an approach has led to a number of difficulties, including a reliance on overly rigid sequencing mechanisms, an inability to account for context sensitivity in behavior, and a failure to address learning. We consider here an alternative framework, according to which the representation of temporal context is facilitated by recurrent connections within a network mapping from environmental inputs to actions. Applying this approach to a specific, and in many ways prototypical, everyday task (coffee-making), we examine its ability to account for several central characteristics of normal and impaired human performance. The model we consider learns to deal flexibly with a complex set of sequencing constraints, encoding contextual information at multiple time-scales within a single, distributed internal representation. Mildly degrading this context representation leads to errors resembling everyday "slips of action". More severe degradation leads to a pattern of disorganization resembling that observed in ideational apraxia. Analysis of the model's function yields novel, testable predictions relevant to both normal and apractic performance. Taken together, the results obtained indicate that recurrent connectionist models may offer a useful framework for understanding routine sequential action.