Confluent talker- and listener-oriented forces in clear speech production

The overall goal of this study was to examine the acoustic-phonetic modifications that characterize clear speech with particular attention to features that are generally taken to reflect the talker-oriented force towards ease-of-articulation. Two specific clear speech features were investigated: the extent of CV coarticulation and vowel space expansion as a function of vowel inventory size. In particular, the purpose of this study was to investigate whether coarticulatory influences are minimized, maintained or exaggerated in clear speech, and whether clear speech hyper-articulation is limited to segments that are likely to be perceptually confused or if clear speech is produced with "global" hyper-articulation. Results showed that clear speech involves both the maintenance of coarticulation, and similar amounts of vowel space expansion for English monolinguals and Spanish- English bilinguals when producing either English or Spanish. The maintenance of coarticulation in clear speech suggests that it is under talker control and likely serves some listener-oriented purpose. Furthermore, the inventory-independent vowel space expansion suggests that talkers spare no effort in producing clear speech and instead "globally" hyperarticulate, even for segments that are unlikely to be perceptually confused with their distant neighbors. These data are interpreted within a framework that views talker- and listener-oriented forces as confluent rather than opposing.