Why is a verb like an inanimate object? Grammatical category and semantic category deficits

Semantic category effects, such as difficulties in naming animate things re lative to inanimate objects, have been explained in terms of the relative w eightings of perceptual and functional features within the semantic represe ntations of these concepts. We argue that grammatical category deficits, su ch us difficulties in naming nouns relative to verbs, can be explained with in the same framework. We hypothesize that verb concepts are richer in func tional than sensory features and present a model of the semantic representa tions of animate nouns. inanimate nouns, and verbs. The model demonstrates that sensory feature damage results in a deficit for naming living things b ut spares verb naming, and functional feature damage results in a deficit f or naming inanimate objects and verbs. We then report the assessment result s of two patient groups. In accordance with the model's predictions. the "v erb spared" patients were consistently worse at naming living things than i nanimate objects, and their definitions of both living and nonliving items were lacking in sensory information We conclude that damage to sensory feat ures in semantic representations causes difficulties in naming concrete nou ns relative to action verbs, and within the grammatical category of nouns, animate items will be more severely affected. Imageability was shown to be a strong predictor of naming performance in the "verb deficit" patients. an d when this variable was controlled no class effect I remained. Production of definitions revealed no differential damage to sensory or functional fea tures, and no consistent effect of animacy in naming was shown. While the m odel suggests that verb deficits might occur in patients fur whom functiona l features are damaged relative to sensory features, we conclude that the " verb deficit" shown in our patients (and potentially in many previously rep orted cases) was an artifact of the lower imageability of verbs in confront ation naming tasks. (C) 2000 Academic Press.