Lexical overlap increases syntactic priming in aphasia independently of short-term memory abilities: Evidence against the explicit memory account of the lexical boost

Speakers show syntactic priming - that is, a tendency to repeat syntactic constructions they have recently comprehended or produced - and this tendency is even stronger when adjacent utterances share the same main verb, termed the lexical boost. Some have suggested that abstract syntactic priming (i.e., with no lexical overlap) derives from implicit learning, whereas the lexical boost derives from explicit short-term memory (STM) for the prime (e.g., Chang, Dell, & Bock, 2006). To address this issue, we assessed twelve people with aphasia (PWA) with varying degrees of STM and language deficits and eleven age-matched healthy control speakers in a syntactic priming experiment. Despite the PWA's difficulty in maintaining phonological, semantic, and structural information, as evidenced by various STM and sentence repetition measures, they showed lexical boost effects comparable to those of healthy speakers. Moreover, the size of the lexical boost was unrelated to the degree of STM deficit, suggesting that the lexical boost does not rely on explicit memory. Alternative explanations for the differing patterns for syntactic priming with and without lexical overlap are discussed.