Speed-accuracy tradeoffs in human speech production

Abstract

Speech motor actions are performed quickly, while simultaneously maintaining a high degree of accuracy. Are speed and accuracy in conflict during speech production? Speed-accuracy tradeoffs have been shown in many domains of human motor action, but have not been directly examined in the domain of speech production. The present work seeks evidence for Fitts’ law, a rigorous formulation of this fundamental tradeoff, in speech articulation kinematics by analyzing USC-TIMIT, a real-time magnetic resonance imaging data set of speech production. A theoretical framework for considering Fitts’ law with respect to models of speech motor control is elucidated. Methodological challenges in seeking relationships consistent with Fitts’ law are addressed, including the operational definitions and measurement of key variables in real-time MRI data. Results suggest the presence of speed-accuracy tradeoffs for certain types of speech production actions, with wide variability across syllable position, and substantial variability also across subjects. Coda consonant targets immediately following the syllabic nucleus show the strongest evidence of this tradeoff, with correlations as high as 0.72 between speed and accuracy. A discussion is provided concerning the potentially limited applicability of Fitts’ law in the context of speech production, as well as the theoretical context for interpreting the results.

Effects of speaking rate, loudness, and clarity modifications on kinematic endpoint variability

“…Although references to speed-accuracy tradeoffs can be frequently found in the speech motor control literature (e.g., Bennett, van Lieshout, & Steele, 2007;Goozee et al, 2005;Guenther, 1995;van Brenk et al, 2013), so far only few studies have directly addressed this assertion. For example, a recent study reported moderate associations between movement time and the estimated difficulty level of an articulator to reach its target (Lammert, Shadle, Narayanan, & Quatieri, 2018) suggesting that talkers adjust their articulatory speed to ensure adequate articulatory precision during speech. Similarly, movement time also varied predictably with the Fitts' index of difficulty when talkers were asked to repeat syllables as fast as possible (Kuberski & Gafos, 2018).…”

Performance of Bimanual Finger Coordination Tasks in Speakers Who Stutter

“…With specific regard to stuttering, when the timing control is less demanding, such as is the case for slow, deliberate speech, where feedback can be employed to control accuracy, disfluencies are less evident (Andrews et al, 1982;Max et al, 2004). Depending on the rate, speech may rely more on feed-forward control, which is speed-oriented, or it may rely more on feedback control, which is accuracy-oriented (Anderson, 1975;Lammert et al, 2018). Thus, in a motor control sense, normal speech may be closer to the tapping task, while slow, deliberate speech may be closer to the rotation task.…”

Bridging Dynamical Systems and Optimal Trajectory Approaches to Speech Motor Control With Dynamic Movement Primitives

“…The relational structure between these populations is such that the behavior of the controlled systems is consistent with second-order dynamics. This suggests a plausible neural implementation of the more abstract dynamical systems in Task Dynamics (Lammert et al, 2018). Additionally, recent studies have identified dynamical patterns in the neural activity that drives motor behavior (Churchland et al, 2012; Shenoy et al, 2013).…”