Noun-verb dissociations: a multi-faceted phenomenon

If we are looking for dissociations in language processing, nouns and verbs are strong candidates. In normal development as well as in developmental and acquired impairments, differences are typically found, usually, though not exclusively, in favour of nouns. In this paper, we re-visit these differences. We argue that the syntactic distinction between nouns and verbs goes hand in hand with phonological and semantic differences. Phonologically, verbs in English tend to have less typical stress patterns than nouns; to be of shorter duration in sentences; and to have fewer syllables. Semantically, a number of factors load differently for verbs and nouns: their conceptual range (with 'things' always mapping onto nouns and 'relations' typically mapping onto verbs); their semantic complexity in terms of the occurrence and number of entities they connect (their 'argument structure'); and the closeness of the mapping between their meanings and non-linguistic concepts (something similar but not identical to the concrete/abstract distinction). We review the reported dissociations showing that all these factors play a role. Normally developing children commonly produce nouns before verbs but this varies depending on semantic, syntactic and phonological characteristics of these categories. Language-impaired children and adults with aphasia commonly show greater limitations in their use of verbs than nouns but patterns of difficulty point to phonological and semantic influences. We conclude that the patterns reported cannot be reduced to any one level of language processing. (C) 2002 Elsevier Science Ltd. All rights reserved.