Tonal center of gravity predicts variation in the interpretation of rising and falling intonation in American English

In English, the pitch trajectory at the end of a phrase distinguishes assertions from questions, through falling versus rising intonation, respectively. This study asks if, within these broad classes, variation in the shape or slope of the pitch excursion is meaningful. Recent work proposes a phonological distinction between two tonally distinct sub-categories of rising intonation: shallow rises favor an assertive interpretation, while steep rises favor a question interpretation (Jeong 2018). We test an alternative analysis, where the probabilistic association between intonation and assertive/inquisitive interpretation arises not from a discrete difference between shallow and steep rises, but from meaningful variation within the rising class. We present findings from two perception experiments where listeners hear short utterances and identify the speaker’s intention to ASK or TELL. Pitch resynthesis (PSOLA) was used to create a stimulus continuum of phrase-final rising and falling F0 trajectories that vary in the slope and shape of monotonic F0 trajectories. Our results show a probabilistic relationship between interpretation (ASK/TELL) and rise variation, but do not support the previously proposed phonological distinction between shallow and steep rises. We propose a more parsimonious model of within-category variation grounded in the Tonal Center of Gravity acoustic measure (Barnes et al. 2012).