Word Order and Adjacency in the Processing of Nested Epistemic Expressions

In this paper, we report three experiments investigating the cognitive mechanisms that underlie the semantic processing of a linguistic construction largely uninvestigated, namely, the nested structure of two epistemic modals in a single clause, as illustrated in the sentence “He may certainly have forgotten” (Lyons, 1977). Two theoretical approaches provide different account for the processing of this structure. Based on a formal linguistic account (Moss, 2015), the meaning of the second modal should be interpreted within the scope of the first modal, and thus, if the first and second modals switch their positions, a change in meaning would be expected. This account is referred to as the “scope account”. In contrast, a good-enough processing account (Ferreira & Lowder, 2016) predicts that the scope of nested modals may not be thoroughly processed, and thus, the order of the modals should not change interlocutors’ interpretation of the nested expression. We examined these two accounts in three experiments that elicited participants’ interpretation of nested epistemic expressions, focusing on whether or not the order and the adjacency of the component modals affected how the nested expressions are interpreted. The repeated absence of the order effect was observed in all three experiments regardless of the adjacency of the modals. This finding challenges the scope account and suggests a holistic processing mechanism in line with the “good enough” processing framework.