Testing theories of plural meanings.

Plural morphology in English is associated with a multiplicity inference. For example, "Emily fed giraffes" is typically interpreted to mean that Emily fed multiple giraffes. It has long been observed that this inference disappears in downward-entailing linguistic environments, such as in the scope of negation. For example, "Emily didn't feed giraffes" does not merely suggest that she didn't feed multiple giraffes, but rather that she didn't feed any. There are three main approaches to explaining this puzzle: the first proposes that the plural is ambiguous, and invokes a preference for stronger meanings; the second derives multiplicity inferences as implicatures; and the third provides a homogeneity-based account. These different approaches can all account for the interpretation of the plural across upward- and downward-entailing environments. They differ, however, in what they predict for three further aspects of the plural: the status of positive and negative plural sentences in singular contexts, children's acquisition of plural meanings, and the relationship between plural meanings and scalar implicatures. In this paper, we report on three experiments investigating adults' and preschool-aged children's interpretation of plural morphology in English. The experiments reveal that participants distinguish positive and negative plural sentences presented in singular contexts, and that adults assign a different status to these positive and negative sentences. It is also observed that children, unlike adults, tend to accept underinformative positive plural sentences in singular contexts - in parallel with their behavior on standard scalar implicatures - while they are relatively more adult-like when it comes to negative plural sentences in the same contexts, showing a tendency to reject the negative sentences. We discuss how the findings of the three experiments are expected on a scalar implicature approach to multiplicity inferences, and the open challenges they pose for the ambiguity and homogeneity approaches.