A study investigated whether children expect color similarity to be less important than form similarity in object label extensions. Twenty 2-year-olds and 20 3-year-olds were asked to sort objects similar in either color or form in two different situations: (1) the "No Label" condition where children were asked to help the puppet put objects that are alike on the same page in the picture-book; and (2) the "Novel Label" condition where children were asked to do the same but told the puppet used words they had never heard before and introduced items with the novel labels. In the first test, both 2-year-olds and 3-year-olds who were offered novel labels for objects sorted them by form similarity. In the second test, the younger children sorted objects more often on the basis of color while the older children sorted almost entirely based on form similarity. These results suggest that color is a relatively uninformative property with regard to objects' category membership, while form appears to be especially predictive of category membership. This may explain why form-based overextension errors are not unusual in children's early use of object labels, while color overextensions are far less common. It may also explain why children tend to learn basic category level labels before those at a higher or lower level of classification. (MSE)