Is buttercup a kind of cup? Hyponymy and semantic transparency in compound words

Hyponymy is a semantic relation of class inclusion (e.g., a cat is an animal; a wildcat is a cat). Compound words are often, but not always, in a hyponymic relationship with the second constituent of the compound, as in wildcat and cat. This paper introduces a set of human ratings of hyponymy for over 2500 English compound words, which will facilitate research on the role of hyponymy in compound word processing and related areas. In the compound word processing literature, the semantic transparency of the compound (i.e., the extent to which the meaning of the constituents is maintained in the compound) is a critical theoretical construct. We investigate the role that hyponymy plays in the semantic transparency of compound words, as well as in the processing of compound words. We find that hyponymy is a critical component of the semantic transparency of both the second constituent (e.g., cat) and the compound as a whole (e.g., wildcat) and somewhat surprisingly also of the first constituent (e.g., wild). Hyponymy also affects the speed of processing of compound words in both lexical decision and naming.