Investigated the effects of age and familiarity on children's adoption of a modeled language rule. A 3 * 2 factorial design was employed, with 3 age levels of 14 Ss each, and a familiar or unfamiliar rule. The oldest groups performed best on measures of both repetition of modeled constructions and production of novel sentences which precisely fitted the relevant rule. Neither rule familiarity nor the Age * Rule interaction had significant effects. Results are discussed in relationship to the hypothesis that language learning is an active problem-solving process which is facilitated by well-developed cognitive skills. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.