Dynamics and kinematics of repetitive speech movements

A standard model of isolated speech movements is thought to be a linear second
order system (Saltzman and Munhall, 1989). Several variations to this model
have been proposed which claim to render isolated as well as sequences of
speech movements more accurately. There are also proposals from other areas of
motor control which aim to render both non-repetitive and repetitive sequences
of not specifically speech movements. We used the Harvard/Haskins database of
regularly-timed speech (Patel et al., 1999) to extract kinematic relations of
jaw and lower lip movements in opening and closing /b, m/ gestures. These
relations are then compared with the via-simulation predicted relations from
linear and nonlinear models of the speech gesture as well as autonomous and
nonautonomous two-dimensional proposed models. In simulations, topological
differences with regard to the kind and the number of the model-specific
attractors (fixed points, limit cycles) are considered. It is shown that, for
the experimental data in this work, none of these models are able to completely
account for the data. Relative time to peak velocity (RTTP) values of closing
movements tend to be higher than values predicted by any fixed point model.
Those models which simulation results indicate are able to generate higher
values of RTTP exhibit other incompatible kinematic relations (e.g., strongly
nonlinear peak velocity vs. movement amplitude relation). We conclude with a
discussion of the extent to which the task at hand uniquely determines the
dynamical regime (repeated isolated gestures vs. limit cycle) underlying the
observed performance. We also review results from our own work with acquiring
similar data, under more controlled conditions (specifically speech rate
controlled), in an attempt to address the nature of the dynamical regime
underlying the movements.

Saltzman, Elliot L. and Kevin G. Munhall (1989). “A dynamical approach to
gestural patterning in speech production”. In: Ecological psychology 1 (4), pp.
333–382. DOI: 10.1207/s15326969eco0104_2.

Patel, Aniruddh D., Anders Löfqvist, and Walter Naito (1999). “The acoustics
and kinematics of regularly timed speech: a database and method for the study
of the P-center problem”. In: Proceedings of the 14th International Congress of
Phonetic Sciences. (San Francisco). Vol. 1, pp. 405–408.