Systematic mappings of sound to meaning: A theoretical review.

The form of a word sometimes conveys semantic information. For example, the iconic word gurgle sounds like what it means, and busy is easy to identify as an English adjective because it ends in -y. Such links between form and meaning matter because they help people learn and use language. But gurgle also sounds like gargle and burble, and the -y in busy is morphologically and etymologically unrelated to the -y in crazy and watery. Whatever processing effects gurgle and busy have in common likely stem not from iconic, morphological, or etymological relationships but from systematicity more broadly: the phenomenon whereby semantically related words share a phonological or orthographic feature. In this review, we evaluate corpus evidence that spoken languages are systematic (even when controlling for iconicity, morphology, and etymology) and experimental evidence that systematicity impacts word processing (even in lieu of iconic, morphological, and etymological relationships). We conclude by drawing attention to the relationship between systematicity and low-frequency words and, consequently, the role that systematicity plays in natural language processing.