This dissertation discusses children's understanding of semantic contribution of the universal quantifier every and its interactions with negation from a logico-semantic perspective. The universal quantifier every evokes an asymmetric entailment pattern in its first and second arguments (e.g., Ladusaw, 1979), which influences both sentential meanings and inferential relations among them. Whereas several studies have revealed children's sophisticated ability to compose the meanings of sentences containing every (e.g., Gualmini 2005), far less is known about whether children's knowledge about every can be extended to the level of meaning comparison, i.e., to the computation of the inferential relations among every-sentences. We thus investigate whether children are able to apply their knowledge about every to the calculation of the inference relations between every-sentences. In particular, this dissertation aims to experimentally examine children's ability to evaluate the inferences between every-sentences.

We first report an experiment featuring the Truth Value Judgment Task (e.g., Crain and Thornton 1998), reconfirming children's adult-like ability to compose individual sentence meanings involving every. We then introduce two novel experimental methodologies, the Prediction-Rephrase Task and the Demand-Fulfillment Task, designed to assess children's ability to evaluate inferences between the entailing and entailed sentences. Three experiments utilizing these new tasks demonstrate that children's highly sophisticated knowledge about every is appropriately applied in comparing meaning relations involving every across-propositionally. Additionally, we present experiments that reveal children's adult-like knowledge regarding the semantic interaction between every and negation (e.g., Ludlow 2002) in both composing and comparing sentential meanings; these findings provide the evidence showing children's adult-like linguistic representations of the sentences, in which the structural relation between every and negation determines the patterns of inferences.

Taken together, these studies demonstrate children's adult-like knowledge regarding the semantics of every that is applied both in the composition and comparison of sentential meanings, as well as their adult-like knowledge about the interaction between every and negation. In addition, our development of the two new experimental methodologies has made possible further steps toward the full understanding of semantic competence in child language, not only at the level of meaning composition but also at the level of meaning comparison.