Higher-Order Logical Reasoning in Preschool Children: Evidence from Intonation and Quantifier Scope.

Background: Logical reasoning in young children is difficult to ascertain experimentally even for single propositional operators. We present a novel argument that four- and five-year old children are capable of reasoning with complex representations containing multiple logical operators. Methods: The argument is based on an interaction between sentence interpretation and intonation. This interaction depends on the computation of logical inferences between the sentence uttered and possible alternative utterances containing proportional generalized quantifiers, and how adults arrive at different interpretations is well understood. The account that explains the interaction predicts that a specific intonation will disambiguate scopal interpretation in sentences with a negation and a universal quantifier, but not in sentences involving two quantifiers. Results: We show that preschool children speaking German are sensitive to the interaction between logical scope of expressions and intonation in the same way as adult speakers. Conclusion: This result entails that preschool children can carry out logical reasoning within a higher order logic.