This is the first study to investigate experimentally how children come to learn mappings between novel phrasal forms and novel meanings: a central task in learning a language. Two experiments are reported. In both studies 5- to 7-year-old children watched a short set of video clips depicting objects appearing in various ways. Each scene was described using a novel verb embedded in a novel construction. Children who watched the videos and heard the accompanying description were able to match new descriptions that used the novel construction with new scenes of appearance. Moreover, our results suggest a facilitative effect for the disproportionately high frequency of occurrence of a single verb in a particular construction (such as has been found to exist in naturalistic input to children). While the fast mapping might be taken as an indication of innate knowledge that is specific to language, analogous effects in non-linguistic categorization tasks suggest that children are acquiring the new phrasal form with general cognitive skills.