Infants Assume Questions Serve an Information-Seeking Function, Link Them to Interrogative Sentences and Differentiate Them From Assertions.

Eye-tracking studies tested the understanding of two types of speech acts (questions and assertions) in 14-, 18-, and 30-month-olds (N = 280; 149 females; ethnicity data collection forbidden, testing in 2021-2024). Experiments involved objects either hidden or visible for a speaker. By 14 months, when the speaker asked questions, infants focused on hidden objects (rs > 0.31). Infants linked novel labels in interrogative sentences to hidden objects by 18 months and novel labels in declarative sentences to visible objects by 14 months (ds > 0.52). Thus, infants assume questions seek information one is lacking, while assertions share information one has access to. Furthermore, infants connect interrogative sentences to questions and declarative sentences to assertions, showing an understanding of communicative form-function relations.