Speed-Accuracy Tradeoffs in Speech Production

Motor actions in speech production are both rapid and highly dexterous, even though speed and accuracy are often thought to conflict. Fitts law has served as a rigorous formulation of the fundamental speed-accuracy tradeoff in other domains of human motor action, but has not been directly examined in the domain of speech production. The present work seeks evidence for Fitts law in speech articulation kinematics by analyzing USC-TIMIT, a large database of real-time magnetic resonance imaging data of speech production. A theoretical framework for considering Fitts law in the domain of speech production is elucidated. Methodological challenges in applying Fitts-style analysis are addressed, including the definition and operational measurement of key variables in real-time MRI data. Results suggest the presence of clear tradeoffs between speed and accuracy 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. Results are discussed with respect to potential limitations of Fitts law in the context of speech production, as well as the theoretical context. Future improvements in application of Fitts law are discussed.