Moment-to-Moment Processing of Complex Sentences by Adults with and without Developmental Language Disorder

. Limited evidence suggests that adults with developmental language disorder (DLD) take different information into account as they process sentences as compared to peers with typical language. The purpose of this study was to evaluate how two factors affect sentence processing in adults with DLD: online storage costs and lexical expectations created by nouns.

. Forty-three adults, 21 with DLD, listened to complex sentences presented word-by-word, and their listening times were recorded. The sentences included either object relative clauses or sentential complements which differed in online storage demands. The main clause subject nouns differed in co-occurrence frequency with "that" in sentences produced by typical adults. Participants completed a running span task to assess verbal working memory capacity.

. Mixed effects models found differences by sentence region. Participants with DLD processed embedded clause verbs faster than participants with typical language, and poorer language ability was associated with faster processing of conjunctions "that" and "which." Participants with greater verbal working memory capacity or typical language were affected by noun co-occurrence frequencies but those with lower working memory or DLD were not.

. The results align with prior findings that verbal working memory capacity influences what information affects moment-to-moment sentence processing. Those with greater capacity appeared to be more affected by temporary ambiguity. As compared to adults with typical language, processing times of adults with DLD were less sensitive to information on words that frequently co-occur with nouns. This aligns with prior findings suggesting that adults with DLD are less sensitive to the frequency of the structures and arguments that co-occur with verbs.