Animals and artifacts may not be treated equally: differentiating strong and weak forms of category-specific visual agnosia.

We examined a categorical dissociation hypothesis of category-specific agnosia using hierarchical regression to predict the naming responses of three agnosia patients while controlling a wide variety of perceptual and conceptual between-category differences. The living-nonliving distinction remained a significant predictor for two of the patients after controlling for all the other factors. For one remaining patient, the categorical variable was not significant once the form-function correlation of different objects was controlled. We argue that the visual system may use various subprocesses at different stages, some of which reflect true categorical organization and some of which reflect a unitary feature-based system that distinguishes kinds.