Frequency-predicted shifts independent of word-specific phonetic details

Abstract

Some sound changes seem to proceed at different rates depending on lexical frequency; these are often interpreted as reflecting phonetically detailed exemplar memories, with changes spreading via lexical diffusion (Pierrehumbert 2002; Bybee 2012). However, such patterns do not necessarily require word-specific phonetic details. Variation associated with lexical frequency also exists when there is no evidence for a change in progress, which might be explained by the process of lexical access: Higher lexical frequency facilitates activation, causing faster and more reduced productions (Gahl et al. 2012, Kahn & Arnold 2012, Jurafsky et al. 2002). This work examines how repeated exposure to particular words influences listeners’ category boundary between aspirated and unaspirated stops in those words. Listeners’ VOT category boundary is lowered after exposure to shortened VOT stimuli and also after exposure to lengthened VOT stimuli. These results suggest that frequency-related sound change can largely be explained by frequency directly influencing reduction in phonetic implementation and perceptual access. The size of the effect differed based on the acoustic characteristics of the exposure stimuli; this may suggest a role of word-specific phonetic details, but could also reflect different levels of activation due to the prototypicality of the stimuli.