A prerequisite to understanding the sensorimotor processes underlying speech production is to identify and characterize experimentally a set of robust behavioral patterns to gain insight into their coordination and control. The goal of this project is to systematically investigate such behavioral patterns attempting to identify specific organizational principles. Speech movements are viewed within a dynamics framework in which articulatory trajectories and other kinematic observables reflect the characteristics of an underlying dynamical system. Significant theoretical constructs are those of an abstract and goal-oriented gesture (e.g., the creation or release of vocal tract constrictions) and the control regime (coordinative structure) that shapes the synergistic activity among a set of functionally-linked articulators. Gestures can be flexibly assembled but may rely on rather strict timing constraints to facilitate their coordination. Experiments are designed within the coordinative structure framework to provide data addressing the following issues: interarticulator coordination and intergestural sequencing, and their stability to mechanical perturbation, interrelationships among the kinematic and electromyographic correlates of articulator motion when behavior is scaled along performance dimensions such as rate, stress, and segmental composition; and similarities between dynamic and kinematic patterns for speech and nonspeech behaviors such as mastication and respiration. The results from these experiments will complement those of the other project areas by providing data relevant to specific phonological and phonetic issues, detailing principled organizational strategies facilitating the modeling efforts, and allowing more refined description of speech movement disorders. In addition to extending our understanding of speech as a specialized biological function, insight will be gained into processes of coordination and control common to many complex motor behaviors.
