Research based on naturalistic and checklist methods has revealed differences between English and Chinese monolingual children in their trajectories of learning nouns and verbs. However, studies based on controlled laboratory designs (e.g., Imai et al., 2008) have yielded a more mixed picture. Guided by a multidimensional view of word learning (in which different mechanisms are weighted and recruited to different extents over development), we examined English- and Mandarin-learning infants' (n = 128) ability to map novel labels to unfamiliar actions and objects. Findings reveal cross-linguistic variations in the "mapping" of words to actions versus objects that are consistent with those found previously with naturalistic and checklist methods. Specifically, English learners were able to map novel labels to both actions and objects at 18 months but to neither actions nor objects at 14 months. In an identical experimental paradigm, Mandarin learners at both 14 and 18 months of age were able to map novel labels to actions but not to objects. Similar patterns were found when infants were grouped based on their vocabulary size. Combined results lend support for a dynamic view of word learning that take into account multiple mechanisms interacting across developmental time with important cultural constraints. (Contains 2 footnotes, 1 table, and 3 figures.)