1Running head: GRADED STRUCTURE IN ADJECTIVE CATEGORIES Accounting for graded structure in adjective categories with valence-based opposition relationships

In contrast to noun categories, little is known about the graded structure of adjective categories. In this study we investigated whether adjective categories show a similar graded structure and what determines this structure. The results show that adjective categories like nouns exhibit a reliable graded structure. Similar to nouns, we investigated if similarity is the main determinant of the graded structure. We derived a low-dimensional similarity representation for adjective categories and found that valence differences in adjectives constitute an important organizing principle in this similarity space. Valence was not implicated in the categories ’ graded structure, however. A formal similarity-based model using exemplars accounted for the graded structure by effectively discarding the valence differences between adjectives in the similarity representation through dimensional weighting. Our results generalize similarity-based accounts of graded structure and highlight a closely-knit relationship between adjectives and nouns on a representational level