When can children speaking Japanese, English, or Chinese map and extend novel nouns and verbs? Across 6 studies, 3- and 5-year-old children in all 3 languages map and extend novel nouns more readily than novel verbs. This finding prevails even in languages like Chinese and Japanese that are assumed to be verb-friendly languages (e.g., T. Tardif, 1996). The results also suggest that the input language uniquely shapes verb learning such that English-speaking children require grammatical support to learn verbs, whereas Chinese children require pragmatic as well as grammatical support. This research bears on how universally shared cognitive factors and language-specific linguistic factors interact in lexical development.

The present research examined how 3- and 5-year-old Japanese children map novel nouns and verbs onto dynamic action events and generalize them to new instances. Studies 1 to 3 demonstrated that although both 3- and 5-year-olds were able to map novel nouns onto novel objects, only 5-year-olds could generalize verbs solely on the basis of the sameness of the action. Study 4 showed that the difficulty young children experience in learning verbs lies mainly in mapping the appropriate element to a verb rather than in encoding and remembering an action itself. The results of this research are related to a long-debated issue of whether noun learning is privileged over verb learning.

The world’s languages draw on a common set of event components for their verb systems. Yet, these components are differentially distributed across languages. At what age do children begin to use language specific patterns to narrow possible verb meanings? English, Japanese, and Spanish-speaking adults, toddlers, and preschoolers were shown videos of an animated star performing a novel manner along a novel path paired with a language appropriate nonsense verb. They were then asked to extend that verb to either the same manner or the same path as in training. Across languages, toddlers (2- and 2 ½-year-olds) revealed a significant preference for interpreting the verb as a path verb. In preschool (3- and 5-year-olds) and adulthood, participants displayed language specific patterns of verb construal. These findings illuminate the way in which verb construal comes to reflect properties of the input language.

Young children often fail to generalize a novel verb based on sameness of action since they have difficulty focusing on the relational similarity across events while at the same time ignoring the objects that are involved. Study 1, with Japanese-speaking 3- and 4-year-olds (N = 28 in each group), found that similarity of objects involved in action events plays a scaffolding role in children's extraction of relational similarity across events when they extend a verb. Study 2, with 4-year-olds (N = 47), further showed that repeated experience of action-based verb extension supported by object similarity leads children to be better able to extend a novel verb based on sameness of action, even without support from object similarity.

Syntax has been noted to play an important role in word learning in English; it distinguishes the fundamental conceptual difference between individuals (coded as proper nouns), nonindividuals (coded as mass nouns), and classes of individuals (coded as count nouns). The Japanese language does not have grammatical markers flagging the distinctions between count nouns and mass nouns, between proper nouns and common nouns, or between singulars and plurals. How Japanese 2- and 4-year-olds assign meaning to novel nouns associated with familiar and unfamiliar animals and inanimate objects was studied in the research reported here. When a novel label was given to an unfamiliar object, children assumed it to be a name for a basic-level object category whether the referent was an animal or an inanimate object. If the named object already had an established name, and if the object was an inanimate object, the children mapped the noun to a subordinate category. When the named object was an animal, however, they tended to interpret the label as a proper name. These results demonstrated that in the absence of useful information from syntax, 2-year-old Japanese children are able to fast map a noun to its meaning by elegantly coordinating word-learning biases and other available sources of information.