Semantic proximity and shape feature integration effects in visual agnosiafor biological kinds

Category specific visual agnosia (CSVA) for biological objects appears to b e caused by a deficit in retrieving structural knowledge. We investigated t he case of IL, a patient who suffers from CSVA, in order to examine the rel ationship between structural and semantic knowledge. Two experiments involv ing synthetic shapes, a visual classification task and a picture-word match ing task, were conducted with IL and 5 neurologically intact subjects. Comp ared to normals, the patient's results in the first task showed no perceptu al categorization deficit, but in the second task they revealed interactive effects of visual structure and of semantic category. The category specifi city of CSVA is explained by the greater semantic proximity between visuall y similar biological objects compared to artefacts. (C) 1999 Academic Press .