Speech rate variation in articulation was observed using electromagnetic articulographic recordings of American English speakers. Each participant produced the sentences “I will be pop/popped on Monday” 16 times at 11 distinct rates cued by a visual meter. Constriction and release gestures for each /p/ in /pɑp(t)/ were parsed using the lip aperture signal, and /ɑ/ gestures from a sensor on the tongue body. We found that some kinematic measures (duration) scaled monotonically with rate, while others (peak velocity) showed non-monotonic (U-shaped) patterns. A nonlinear dynamical model of articulation (Stern & Shaw, 2025) was fit to each movement. We found that each of the two control parameters of the model scaled monotonically with rate: r (controlling rapidity) increased at faster rates, and T (controlling spatial target) became less extreme (larger for constrictions, smaller for releases) at faster rates. The presence of the second coda consonant (in /pɑpt/) also increased T, though in speaker-idiosyncratic ways. Importantly, movements simulated from the model using the fitted parameters reproduced both the monotonic and non-monotonic kinematic patterns, providing evidence that the complex articulatory timing relations underlying speech rate variation can arise from monotonic parameter scaling of a nonlinear dynamical control system. Work supported by NSF-BCS2141275.
Stern et al. (Wed,) studied this question.