The interaction of notional number and morphophonology in subject–verb agreement: A role for working memory

Research shows that cross-linguistically, subject–verb agreement with complex noun phrases (e.g., The label on the bottles) is influenced by notional number and the presence of homophony in case, gender, or number morphology. Less well-understood is whether notional number and morphophonology interact during speech production, and whether the relative impact of these two factors is influenced by working memory capacity. Using an auditory sentence completion task, we investigated the impact of notional number and morphophonology on agreement with complex subject noun phrases in Dutch. Results revealed main effects of notional number and morphophonology. Critically, there was also an interaction between morphophonology and notional number because participants showed greater notional effects when the determiners were homophonous and morphophonologically ambiguous. Furthermore, participants with higher working memory scores made fewer agreement errors when the subject noun phrase contained homophonous determiners, and this effect was greater when the subject noun phrase was notionally singular. These findings support the hypothesis that cue-based retrieval plays a role in agreement production, and suggests that the ability to correctly assign subject–verb agreement—especially in the presence of homophonous determiners—is modulated by working memory capacity.