The wanna facts are a classic Poverty of Stimulus (PoS) problem: wanna is grammatical in certain contexts (Who do you want PRO to play with?) but not others (Who do you want who to play with you?). On a standard analysis, "contraction" to wanna is blocked by some empty constituents (WH-copies) but not others (PRO). All empty constituents are inaudible, so it has been unclear how restrictions on them could be learned. Children's reported knowledge of the wanna facts (Crain & Thornton, 1998) has therefore been attributed to a principle of Universal Grammar (UG). In two experiments, we demonstrate that children's use of wanna is not in fact adultlike and that error rates are modulated by the frequency of the embedded verb (play above). These results suggest that if there is a UG principle, children appear not to know that it is relevant, raising important questions about what learning mechanisms enable children to circumvent the input's apparent poverty.