Abstract

In order for children to acquire language as rapidly as they do, they must have biases that enable them to rule out many alternative hypotheses for the meanings of a word and that lead them instead to focus on hypotheses that are reasonably likely to be correct. One way children initially constrain word meanings is to assume that words are mutually exclusive - that each object has only one label. Although a mutual exclusivity assumption can be useful in word learning, it interferes the children's understandings of class inclusion relations. Because class inclusion relations violate a mutual exclusivity assumption. The study 1 examined whether subjects assume that each object has only one category label. The studies 2, 3, 4 focus on whether subjects accept two label for the same object if they believe that the label denote categories from different levels of a hierarchy. Together, these studies examined whether subjects accept two labels for the same object when one object-one label strategy is no longer possible. The result of study 1 showed that both 3- and 5-year-old children and adults assume words are mutually exclusive-that each object has only one label. This is surprising because adults undoubtedly know many word that name overlapping categories(e. g., dog, animal, pet). This finding suggests that a mutual exclusivity assumption would be invariant cognitive constraints. The result of study 2, 3, 4 revealed that 3-and 5-year-old children made quite a few errors in learning the hierarchical relations among categories, and the majority of the errors were treating the labels as mutually exclusive subsets. But they have accepted two labels for the same object if experimenter repeatedly explains about the relations. Together, the result of studies showed that subjects accepted two labels for the same object when one object- one label strategy is no longer possible. These results indicate that children may have trouble to deal with the hierarchically organized category terms which violate a mutual exclusivity assumption. Together, these results indicate that 3-year-old children have the capacity to override a mutual exclusivity assumption as long as there is enough evidence that two names denote the same object.