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[strikethrough] 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"). 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.