Preschool children\u27s use of the mutual exclusivity principle during extension of words applied to familiar and unfamiliar nonsolid substances

Two experiments assessed children\u27s interpretations of novel words applied to nonsolid substances. In particular, the principle of mutual exclusivity was tested. This principle holds that, if a child already knows a label for an object, then a new label for that object should be rejected. The present research extended the study of the mutual exclusivity principle to children\u27s acquisition of words for nonsolid substances and tested for age-related changes in children\u27s reliance upon mutual exclusivity. ^ In Experiment 1, 48 children between 3 and 5 years viewed substances that were either familiar (e.g., playdoh) or unfamiliar (e.g., spackling compound). Each substance possessed some distinctive property (e.g., glitter) and was referenced with a novel word. A forced choice assessment was made of whether the children interpreted the novel word as a name for a substance or its distinctive property. Children extended novel words to the distinctive property more often in the familiar than in the unfamiliar condition. This result is consistent with the principle of mutual exclusivity. ^ Experiment 2 was a more stringent test of the mutual exclusivity principle. As in Experiment 1, 48 children between 3 and 5 years viewed substances that were either familiar or unfamiliar. Again, each substance possessed some distinctive property and was referenced with a novel word. An assessment using sequential presentation was made of whether the children were willing to extend the novel word to the substance, the distinctive property, both substance and property, or neither. In the familiar substance condition, children extended novel words more to the distinctive property than to the substance. In the unfamiliar substance condition, children extended novel words more to the substance than to the distinctive property. These patterns are those predicted by mutual exclusivity. However, in Experiment 2 there was no evidence that the youngest preschoolers used the mutual exclusivity assumption, and the strongest evidence occurred in the oldest age group tested. The results were discussed in terms of age-related changes in children\u27s reliance on the mutual exclusivity principle and directions for further research.