Facilitation by Variation: Right-to-Left Learning of English Yes/No Questions.

This study advances the hypothesis that optional structural variation in language facilitates syntactic learning (facilitation-by-variation). Support for this is provided by a right-to-left-elaboration acquisition model for English yes/no questions (YNQs). Previous studies have focused on the acquisition of ''inverted'' YNQs, a cornerstone of nativist theories of language development. Data from five American children (1;3 to 5;1) and their parents show that children hear a range of adult questions (Coming?You coming?Are you coming?), not all inverted. These variants are ordered from structurally least complex noncanonical forms to complex canonical inverted forms. I use state-of-the-art econometric techniques to estimate breakpoints in YNQ time series and show that noncanonical questions emerge early in children's speech and facilitate acquisition of canonical ones. This incremental structure-building process relies on an adjunction strategy that augments noncanonical questions with initial auxiliaries and subjects. Development proceeds incrementally from right to left to derive auxiliary-initial structures.