The Structure and Plasticity of Phonetic Categories Across Languages and Modalities

Abstract

Speech sounds contrast on many acoustic dimensions. The constellation of acoustic "cues" defining a given sound contrast is language-specific, such that the "same" sounds in different languages are actually realized slightly differently. Furthermore, even within the same language group, speakers and listeners exhibit considerable variability in their use of acoustic cues. This work explores acoustic cue use in stop voicing contrasts across languages (Spanish, English, and Korean) and modalities (production and perception). A first group of experiments target "baseline" cue weights, or how speakers and listeners use multiple acoustic dimensions to define native and foreign sound contrasts in production and perception. A second set of experiments investigates how listeners modify their definitions of these categories in order to accommodate to changes in the input (e.g. a speaker with an "accent"), and in particular, how baseline cue-weighting strategies can influence and direct these adaptation patterns. Along with comparison of cross-linguistic differences in cue use, all of the studies focus on variability within language groups and examine the relationship between perception and production on an individual level. Taken together, the studies provide a detailed comparison of the way speakers and listeners make use of multiple acoustic cues cross-linguistically. The experiments give a comparative picture of the extent of between- and within-language variation in "baseline" cue weights across three languages and provide insight into the processes by which listeners adapt or "tune" their phonetic categories when confronted with changes in what they are hearing. The work highlights the complexity of the perception-production interface, as well as the interplay between language-specific knowledge, general learning mechanisms, and general auditory factors in how listeners use acoustic cues to define and modify their speech sound categories.