Tonal Center of Gravity: A global approach to tonal implementation in a level-based intonational phonology

Abstract

Recent evidence that pitch-movement shape can influence perceived alignment of rising (LH) pitch accents in several languages appears to challenge the well-established level-based approach to intonation embodied in the AM model, wherein it is typically assumed that the alignment and scaling of well-defined turning points (TPs) in the F₀ contour are the primary phonetic correlates of contrastive accent category. Here we present the results of two experiments, arguing that a new approach to tonal implementation succeeds in reconciling these apparent contradictions. This approach, based on the notion of a perceptual reference point called Tonal Center of Gravity (TCoG), treats information about contour shape and TP-localization not in ‘either-or’ terms, but rather as two sets of cues working in a fundamentally synergistic way toward a single perceptual end: the alignment and scaling of TCoG. Experiment 1 shows that TCoG-based models can perform better at distinguishing productions of English L+H* and L*+H pitch accents than comparable TP-only-based models; Experiment 2 shows that TCoG is more robust than TP-only-based models to ambiguities in TP localization commonly encountered in F₀ signals from natural speech. TCoG is shown to capture key insights of movement-based approaches to intonation, without abandoning the central advantages of level-based approaches like AM.