Sometimes a noun is just a noun: Comments on Bird, Howard, and Franklin (2000)

Bird, Howard, and Franklin (2000) have proposed a semantic-conceptual expla nation of grammatical category-specific deficits that attributes impairment s in noun and verb processing to two distinct mechanisms. According to thei r account, apparent deficits in verb production are not category specific, but rather result from the lower imageability of verbs compared to concrete nouns. Noun deficits are said to result from differences in the distributi on of semantic feature types such that damage to sensory features results i n disproportionate impairments in naming nouns, especially animate nouns, c ompared to verbs. However, this hypothesis, which we call the "extended sen sory/functional theory" (ESFT), fails on several counts. First, the assumpt ion that representations of living things are more heavily freighted with s ensory features than are those of nonliving objects does not have any relia ble empirical basis. Second, the ESFT incorrectly predicts associations bet ween deficits in processing sensory features and living things or functiona l features and nonliving things. Finally, there are numerous cases of patie nts with grammatical category-specific deficits that do not seem to be cons istent with damage at the semantic level. All of this suggests that the ESF T is nor a useful model for considering grammatical (or semantic) category- specific deficits. (C) 2001 Academic Press.