Nouns and adjectives also differ in their association with the linguistic form of questions about objects. Different words, for example what is it versus what color is it? are used to ask about object categories and object properties. Dimensional adjectives also differ among themselves in this regard: what color is it asks for a color word as an answer; how does it feel? asks for a description of texture. [BS93] have shown that young children are sensitive to these associations between questions and the class of possible answers prior to their understanding of the meanings of the individual words. Thus in learning common nouns and adjectives, learners do not just map objects to words but they also map linguistic inputs to linguistic outputs.
It is not immediately clear whether these word-to-word associations favor nouns or adjectives. However, given the overlap among the to-be-learned categories, we can be certain that they are crucial to learning. A big, red, furry dog is a member of the category BIG, the category RED, the category FURRY, and the category DOG. It is the linguistic input, the question ``what is it?'' or ``what color is it?,'' that specifies the relevant class of linguistic outputs. These word-to-word maps partition all the categories that the child is learning into larger proto-syntactic categories --- into ``noun categories,'' ``color categories,'' ``size categories,'' and ``texture categories.'' In stages of incomplete learning, do these word-to-word maps also create a distinction between nouns and adjectives such that adjectives are confused across dimensions but are not confused with nouns?
In what follows, we demonstrate that a simple associative device that approaches the task of learning about nouns and adjectives in the very same way will nonetheless show a noun advantage and also the pattern of within-category confusions shown by children. In addition, we separately investigate the roles of category shape, volume, overlap, and word-word associations in forming this developmental trajectory.