This paper explores the learnability of English indefinite any, Dutch modal verb hoeven, and Mandarin Chinese (WH-)indefinite/pronoun shenme. These three expressions, belonging to different syntactic categories in different languages, have been referred to as Negative Polarity Items (NPIs) in the literature, as they are all restricted to contexts that in some sense count as negative although there are differences in the types of semantic environment that may license them. By investigating the distribution of these three expressions in both child and child-directed speech recorded in the CHILDES database (MacWhinney 2009), this paper argues that children in their acquisition of these NPIs employ the same conservative widening learning strategy (Berwick and Weinberg 1986; Manzini and Wexler 1987), which prevents them from overgeneration. A two-stage acquisition process is detected for each of the three NPIs. However, distinct learning pathways are found, which we take as evidence indicating different underlying analyses of these expressions at different stages in child language. Taking into consideration the input characteristics, the distributional patterns of the three expressions in adult grammar, and the children’s lexical development, we hypothesize what the analyses of any, hoeven, and shenme at different acquisition stages look like. This provides us with a different view of the nature, or the reason underlying the restricted distribution of these expressions in adult language.