Word frequency effects in sound change as a consequence of perceptual asymmetries: An exemplar-based model

Empirically-observed word frequency effects in regular sound change present a puzzle: how can high-frequency words change faster than low-frequency words in some cases, slower in other cases, and at the same rate in yet other cases? We argue that this puzzle can be answered by giving substantial weight to the role of the listener. We present an exemplar-based computational model of regular sound change in which the listener plays a large role, and we demonstrate that it generates sound changes with properties and word frequency effects seen in corpora. In particular, we consider the experimentally-supported assumption that high-frequency words may be more robustly recognized than low-frequency words in the face of acoustic ambiguity. We show that this assumption allows high-frequency words to change at the same rate as low-frequency words when a phoneme category moves without encroaching on the acoustic space of another, faster than low-frequency words when it moves toward another, and slower than low-frequency words when it moves away from another. We discuss how these predicted word frequency effects apply to different types of sound changes that have been observed in the literature. Importantly, these frequency effects follow from assumptions regarding processes in perception, not production. Frequency-based asymmetries in perception predict different frequency effects for different kinds of sound change.