Number maintenance in subject-verb agreement: evidence from Basque

In this paper, we investigate whether number is actively maintained as part of matrix subject-verb dependency establishment, and whether it is active enough to be used to resolve temporary number ambiguity of an interpolated noun. In a visual world paradigm, we tested whether number-ambiguous Basque nouns within embedded relative clauses can be disambiguated by the number of the matrix subject-verb dependency actively maintained over them. We manipulated the number of the matrix subject (singular/plural), and measured the proportion of looks toward singular/plural images in the moment when the number-ambiguous noun is heard (and still not disambiguated). The analysis showed that the proportion of looks followed the matrix subject number, as the plural bias increases significantly in the plural matrix subject condition, implying active maintenance of the number feature. These findings add to the literature on the content of the maintained representation in subject-verb dependency establishment, showing that number information is actively maintained, and they don't align with cue-based sentence comprehension models that presume matrix verb maintenance in an inactive, out-of-focus state. We also demonstrate that the parser uses available morphosyntactic information of items kept active in working memory in order to resolve temporary ambiguity.