Non-sentential utterances (NSUs), utterances that lack an overt verbal (more generally predicative) constituent, are common in adult speech. This paper presents the results of a corpus study of the emergence of certain classes of NSUs in child language, based primarily on data from the Manchester Corpus from CHILDES. Our principal finding is the late short query effect: the main classes of non-sentential queries (NSQs) are acquired much later than non-sentential answers (NSAs). At a stage when the child has productive use of sentential queries, and has mastered elliptical declaratives and the polar lexemes ‘yes’ and ‘no’, non-sentential questions are virtually absent. This happens despite the fact that such questions are common in the speech of the child's caregivers and that the contexts are ones which should facilitate the production of such NSUs. We argue that these results are intrinsically problematic for analyses of NSUs in terms of a single, generalized mechanism of phonological reduction, as standard in generative grammar. We show how to model this effect within an approach of dialogue-oriented constructionism, wherein NSUs are grammatical words or constructions whose main predicate is a contextual parameter resolved in a manner akin to indexical terms, the relevant aspect of context being the discourse topic. We sketch an explanation for the order of acquisition of NSUs, based on a notion which combines accessibility of contextual parameters and complexity of content construction.