Articulatory dynamics and stability in multi-gesture complexes

Speech production involves combined actions of multiple coordinated articulatory gestures. The atomic linguistic units are elegantly coupled with one another to yield a structured spatiotemporal realization of the gestural components of speech, thereby enabling humans to perceive and parse language effortlessly. The goal of this dissertation is to develop our theoretical understanding of the linguistic representation of articulatory coordination in speech production, drawing on an interdisciplinary approach incorporating phonetics, phonology, biomedical imaging, computational modeling, and a dynamical systems approach to motor control. The project undertakes four empirical real-time MRI (rtMRI) experiments to understand how contrastive linguistic ?molecules??focusing on segment-sized multi- gesture complexes?interact with positional and phrasal variation in speech, followed by modeling analyses of the self-organization and coordination among these interacting levels of linguistic structure. ? Specifically, this dissertation undertakes a kinematic examination of intergestural timing stability within multi-gesture segments such as ejectives, implosives, and nasals that may possess specific temporal goals critical to their realization. Using rtMRI speech production data from Hausa and Korean, the dissertation illuminates speech timing among oral constriction and larynx/velum actions within segments and the role this intergestural timing plays in realizing phonological contrast and processes in varying prosodic contexts. Results demonstrate that within such segment-sized gestural molecules coordination is inherently stable due to their specific internal intergestural coupling relations. We successfully model the empirical findings on timing?in particular distinct patterns of timing variability?via a dynamical coupling architecture or ?graph? among the component gestures. The experimental and computational assessment of coordination in multi-gesture structures can reveal the role of coupling relations and timing variability in phonological representation as realized in a variety of syllabic and prosodic environments. This dissertation furthers our linguistic knowledge of how the basic atoms of speech are synergistically built up to produce meaningful speech sounds and to convey linguistic information.