In a series of studies children show increasing mastery of irregular plural forms (such as "mice") simply by producing erroneous over-regularized versions of them (such as "mouses"). We explain this phenomenon in terms of successive approximation in imitation: Children over-regularize early in acquisition because the representations of frequent, regular plural forms develop more quickly, such that at the earliest stages of production they interfere with children's attempts to imitatively reproduce irregular forms they have heard in the input. As the strength of the representations that determine children's productions settle asymptotically, the early advantage for the frequent regular forms is negated, and children's attempts to imitate the irregular forms they have observed become more likely to succeed (a process that produces the classic U-shape in children's acquisition of plural inflection). These data show that children can acquire correct linguistic behavior without feedback in a situation where, as a result of philosophical and linguistic analyses, it has often been argued that it is logically impossible for them to do so. (Contains 10 figures and 4 notes. A derivation of closed-form solutions for the associative strength predicted by the learning curves of a model for irregular and regular noun forms is appended.) [Additional funding for this article was provided by a Stanford Graduate Fellowship.]