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Abstract: Most models of cognitive processing assume a considerable amount of built-in structure in the cognitive system, such as modality-specific semantic systems. Such structural distinctions are thought to be necessary to account for various neuropsychological dissociations, including the selective impairment of visual object naming with spared tactile naming and visual gesturing, known as optic aphasia. A distributed connectionist simulation is presented in which optic aphasia occurs following damage as a result of more graded representational specialization. This specialization emerges through learning under the combined influence of two general factors: the relative systematicity of mappings between input and output modalities, and a topographic bias favoring short connections. The results raise the possibility that much of the structure of the lexical/semantic system can be derived from general learning principles and need not assumed a priori.
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