How we speak when we speak to a beat: The influence of temporal coupling on phonetic enhancement

Abstract

Stressed syllables in languages which have them tend to show two interesting properties: They show patterns of phonetic ‘enhancement’ at the articulatory and acoustic levels, and they also show coordinative properties. They typically play a key role in coordinating speech with co-speech gesture, in coordination with a musical beat, and in other sensorimotor synchronization tasks such as speech-coordinated beat tapping and metronome timing. While various phonological theories have considered stress from both of these perspectives, there is as yet no clear explanation as to how these properties relate to one another. The present work tests the hypothesis that aspects of phonetic enhancement may in fact be driven by coordination itself by observing how phonetic patterns produced by speakers of two prosodically-distinct languages—English and Medʉmba (Grassfields Bantu)—vary as a function of timing relations with an imaginary metronome beat. Results indicate that production of syllables in time (versus on the ‘offbeat’) with the imaginary beat led to increased duration and first formant frequency—two widely observed correlates of syllable stress—for speakers of both languages. These results support the idea that some patterns of phonetic enhancement may have their roots in coordinative practices.