Selective impairment of knowledge underlying un- prefixation: further evidence for the autonomy of grammatical semantics

This paper focuses on grammatical semantics, which is a level of linguistic representation that lies at the interface between syntactic categories and conceptual categories. We report a series of neuropsychological experiments that investigated the semantic constraints on the English verbal un- prefixation construction. In order for a verb to occur in this construction, it must designate an event which involves the creation of a constricted, reversible spatial configuration—e.g. wrap–unwrap, buckle–unbuckle, and clog–unclog, but not float–*unfloat, boil–*unboil, or fluff–*unfluff. Other features of verb meaning are completely invisible to the construction—e.g. the idiosyncratic features that distinguish between wrap, buckle, and clog. Of six brain-damaged patients who were studied, two exhibited the following dissociation. On the one hand, they performed well on a verb–picture matching test that required them to discriminate between subtle features of verb meaning that are not relevant to un- prefixation. On the other hand, they failed a grammaticality judgment test that required them to determine whether the very same verbs satisfy the narrow semantic criteria for the construction. A final control test demonstrated that their errors on the judgment test were not due to problems with certain task demands, but were instead most likely due to an impairment that selectively affected their knowledge or processing of grammatical semantics.