Category specificity in normal recall : investigations of the verbal and visual domain




Bukach, Cindy Myrene.

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Patients with category-specific agnosia (CSA) of the biological type have a disproportionate deficit in recognizing objects from biological categories. Bukach et al. (in press) have shown that a similar pattern of category specificity (CS) arises in normal subjects due to the interaction of structural and conceptual knowledge in the episodic retrieval of object knowledge. The current set of studies extends these findings in two ways: The first series of 4 experiments uses the newly learned attribute recall developed by Bukach et al. to investigate CS in the verbal modality. When word reading is mediated by meaning, recall of newly learned attributes assessed in the verbal modality showed a CS pattern, just as it does in patients with CSA of the biological type.. The second serie.s of 3 experiments examines recognition of object form and the nature of structural similarity by using novel stimuli that vary in the number of structural dimensions that are required to uniquely identify an object. I demonstrate that structural similarity can be understood as the proximity of exemplars in a multidimensional space defined by the diagnostic structural features that have been integrated in the current task. Competition of retrieved episodes based on their structural similarity comes from 2 sources: When the values of diagnostic dimensions are poorly specified, errors reflect competition from exemplars that are close (dimensional proximity). When an insufficient number of diagnostic dimensions are integrated, errors reflect competition from exemplars that share values on diagnostic dimensions (dimensionuZpaucity). I also present preliminary evidence that conceptual relatedness modulates the structural integration process. These results are related to CSA of the biological type, and are discussed in terms of an episodic model of object recognition in which object information is retrieved and integrated from distributed episodic memories.