Previous research suggests that children learning a variety of languages acquire similar early noun vocabularies and do so by similar and universal processes. We report here results from two studies that show differences in the early noun learning of English- and Japanese-speaking children. Experiment 1 examined the relative numbers of animal names and object names in vocabularies of English-speaking and Japanese-speaking children. English-speaking children's vocabularies were heavily lopsided with many more object than animal names whereas Japanese-speaking children's vocabularies were more (...) evenly balanced. Experiment 2 used a novel noun extension task to examine what young children know about the different organizations of animal and artifact categories. The results suggest that early learners of English but not Japanese over-generalize what they know about object categories to animal categories. The role of culture, input and linguistic structure in early noun acquisitions is discussed. (shrink)