Quantifying Spatial and Temporal Variability of Clear and Loud Speech Produced While Performing a Concurrent Visuomotor Task

The purpose of this research note was to quantify the impact of concurrent performance of an attention-demanding secondary task on utterance-to-utterance movement variability associated with higher effort speaking styles, namely, clear and loud speech. Lip and jaw kinematics collected as part of a prior study were analyzed. Participants repeated "Buy Bobby a puppy" using habitual, loud, and clear speech styles in isolation and while performing a secondary tracking task. The lip aperture (LA) signal was segmented based on opening and closing gestures associated with the utterance. The standard deviation of each segment duration was calculated to quantify temporal variability. To quantify spatial variability, each segment was first time normalized. The mean standard deviation of the overlapping time-normalized LA amplitudes was computed for each segment from the repetitions produced in each speech style and condition (speaking in isolation vs. speaking while tracking). A relative measure of spatial variation was also computed to account for the potential impact of articulatory scaling. Clear speech was associated with greater temporal and spatial variability than the habitual and loud styles. In the habitual style, talkers also exhibited a slight reduction in absolute spatial variability when speaking while tracking compared to speaking in isolation. The reduction in absolute spatial variability was likely associated with the concomitant reduction in LA range of motion, as there was no change in the relative spatial variability between conditions. The current investigation expands prior work by quantifying spatial and temporal characteristics of different speaking styles performed in isolation and while concurrently performing an attention-demanding visuomotor task.