The issue addressed in this project is the nature of phonological representations, output goals, and processes used in planning and producing speech articulation. Answers to these questions have implications for our understanding of the basic architecture of the speech production planning process, and are therefore relevant for understanding normal and disordered speech production, as well as speech sound acquisition and speech technology.
The overall project objectives are to provide converging evidence for representations, goals and processes used in planning speech production 1) via experimental tests of predictions for patterns of speech articulation of alternative theories, and 2) via a comparison of articulatory predictions of computational models based on particular (sets of) core theoretical assumptions.
The experiments provide tests of a) symbolic vs. spatiotemporal phonological representations, b) separate phonological and phonetic planning processing components, c) acoustic vs. articulatory goals, d) the nature of speech movement coordination, d) separate representation of spatial vs. temporal information vs. integrated spatiotemporal representations, and e) Lee's General Tau theory of movement planning, coordination, and generation. General Tau Theory has strong support in the non-speech motor literature, but is new to the field of speech science.
The computational modeling work includes 1) the development of a flexible, modular platform allowing for parallel implementation, testing, and comparison of competing theoretical assumptions in terms of
model outputs, and 2) the development of a computational implementation of new approach to speech articulation planning based on symbolic phonological representations, phonology-extrinsic timing, as well as separate Phonological Planning, Phonetic Planning, and Motor-Sensory Implementation components, proposed by Turk & Shattuck-Hufnagel in their Phonology-Extrinsic Timing, 3 Component approach (XT/3C). Key features of Phonetic Planning in this new approach are 1) the use of General Tau Theory in modeling the time-course of articulatory movements, which presents a departure from alternative state-of-the art dynamic models based on mass-spring systems, and 2) the reliance on Optimal Control Theory for accounting for systematic phonetic variability due to competing task demands.
