Why can’t we say "the asleep cat"? There is a class of adjectives in English, all of which start with a schwa (e.g. “alone", “asleep", away", etc.), that cannot be used attributively in a prenominal position. How to learn negative constraints has been a long standing problem in the study of language. The problems with using indirect negative evidence (e.g., Boyd & Goldberg 2011, Language) are well known in the traditional literature (Pinker 1989, MIT Press) but become even more serious when the quantitative aspects of child directed input are taken into account. By contrast, we show that children can use positive data to establish the negative distributional properties of this class of adjectives, and broad linguistic generalization remains the central problem of language acquisition (Yang 2016, MIT Press).