Dynamics of intergestural timing: a perturbation study of lip-larynx coordination

Abstract

In this study, downward-directed mechanical perturbations were applied to the lower lip during both repetitive (/...paepaepae.../) and discrete (/pe'saepaepl/) utterances in order to examine the perturbation-induced changes of intergestural timing between syllables (i.e., between the bilabial and laryngeal gestures for successive /p/'s) and within phonemes (i.e., between the bilabial and laryngeal gestures within single /p/'s). Our findings led us to several conclusions. First, steady-state (phase-resetting) analyses of the repetitive utterances indicated both that "permanent" phase shifts existed for both the lips and the larynx after the system returned to its pre-perturbation rhythm and that smaller steady-state shifts occurred in the relative phasing of these gestures. These results support the hypothesis that central intergestural dynamics can be reset by peripheral articulatory events. Such resetting was strongest when the perturbation was delivered within a "sensitive phase" of the cycle, during which the downwardly directed lower-lip perturbation opposed the just-initiated, actively controlled bilabial closing gesture for /p/. Although changes in syllable duration were found for other perturbed phases, these changes were simply transient effects and did not indicate a resetting of the central "clock." Second, analyses of the transient portions of the perturbed cycles of the repetitive utterances indicated that the perturbation-induced steady-state phase shifts are almost totally attributable to changes occurring during the first two perturbed cycles. Finally, the transient changes in speech timing induced by perturbations in the discrete sequences appeared to share a common dynamical basis with the changes to the repetitive sequences. We conclude by speculating on the type of dynamical system that could generate these temporal patterns.

Dynamic action units slip in speech production errors

“…For example, the upper lip, lower lip, and jaw appear to work cooperatively (and compensatorily) to achieve lip closure (Kelso, Tuller, Vatikiotis-Bateson, & Fowler, 1984). Similar studies using phase-resetting techniques have demonstrated compensation in the temporal domain (Saltzman, Löfqvist, Kay, Kinsella-Shaw, & Rubin, 1998). Based in part on such studies (as well traditional phonological investigations into how words in a language are systematically differentiated from one another and how they are modified when they are produced in different contexts), it has been proposed that utterances can be decomposed into sets of dynamically defined units of constriction action, called gestures (Browman & Goldstein, 1992.…”

“…15 It is worth noting in this regard that mechanical perturbations delivered to the lower lip during speaking have been found to induce compensatory patterns in both repetitive and non-repetitive utterances that appear to be governed by the same underlying dynamical processes (Saltzman et al, 1998).…”

Limb versus Speech Motor Control: A Conceptual Review

“…When the offset of the perturbation occurred during the /p/, the subsequent vowel was lengthened. In a follow-up investigation (Saltzman et al, 1992;Munhall et al, 1994), unexpected perturbations were applied at three different points in time: just before the preceding vowel offset, early during closure, and late in the oral closure, that is, close to the release. In all cases, a longer acoustic Voice Onset Time (VOT) and shorter closure duration were found in the perturbed condition.…”

Interarticulator cohesion within coronal consonant production

“…The assumption is that the task-specific organizationally invariant timing of composite articulators is achieved by a motor program which functiona͒ Portions of this work were presented at the 15th International Congress of Phonetic Sciences, Barcelona, Spain, August 2003. b͒ Author to whom correspondence should be addressed. Electronic mail: timo@ipds.uni-kiel.de ally organizes multiarticulate speech movements for a phonetic gesture, while local parameters of the pattern, such as speech tempo, are left to vary freely and are considered parameters of the program ͑see Shaiman et al, 1995͒. The timing between the executing organs is assumed to be almost invariant and stronger for gestures within a phoneme than between phonemes ͑see Saltzman et al, 1998͒. The evidence for different degrees of cohesion, termed "glue" by Saltzman et al ͑2000͒, was found by perturbation experiments: the relative timing was shifted to a lesser degree when the perturbation occurred within an actively controlled gesture rather than at the borders.…”