Showing papers by "Kevin G. Munhall published in 1985"

Control of rate and duration of speech movements

Abstract: A computerized pulsed‐ultrasound system was used to monitor tongue dorsum movements during the production of consonant‐vowel sequences in which speech rate, vowel, and consonant were varied. The kinematics of tongue movement were analyzed by measuring the lowering gesture of the tongue to give estimates of movement amplitude, duration, and maximum velocity. All three subjects in the study showed reliable correlations between the amplitude of the tongue dorsum movement and its maximum velocity. Further, the ratio of the maximum velocity to the extent of the gesture, a kinematic indicator of articulator stiffness, was found to vary inversely with the duration of the movement. This relationship held both within individual conditions and across all conditions in the study such that a single function was able to accommodate a large proportion of the variance due to changes in movement duration. As similar findings have been obtained both for abduction and adduction gestures of the vocal folds and for rapid voluntary limb movements, the data suggest that a wide range of changes in the duration of individual movements might all have a similar origin. The control of movement rate and duration through the specification of biomechanical characteristics of speech articulators is discussed.

Characteristics of Velocity Profiles of Speech Movements

Abstract: The control of individual speech gestures was investigated by examining laryngeal and tongue movements during vowel and consonant production. A number of linguistic manipulations known to alter the durational characteristics of speech (i.e., speech rate, lexical stress, and phonemic identity) were tested. In all cases a consistent pattern was observed in the kinematics of the laryngeal and tongue gestures. The ratio of maximum instantaneous velocity to movement amplitude, a kinematic index of mass-normalized stiffness, was found to increase systematically as movement duration decreased. Specifically, the ratio of maximum velocity to movement amplitude varied as a function of a parameter, C, times the reciprocal of movement duration. The conformity of the data to this relation indicates that durational change is accomplished by scalar adjustment of a base velocity form. These findings are consistent with the idea that kinematic change is produced by the specification of articulator stiffness. A fundamental problem in the study of skilled movement is how to identify the characteristics of the functional units of motor control. Nowhere is this problem more apparent than in the study of speech production, an activity that involves the coordination of a number of different articulatory systems as well as the implementation of a complex symbol structure. Although there are no universally accepted techniques for the decomposition of such complex systems, a productive strategy has been to identify those aspects of movements that are invariant to manipulations of movement amplitude, duration, accuracy, and so forth. (See Keele, 1981, and Kelso & Tuller, 1984, for reviews.) The assumption is that these behavioral invariances

An examination of intra-articulator relative timing.

Abstract: The relative timing of consonant and vowel related movements of the tongue dorsum across variations in stress patterns was examined in two subjects using a computerized pulsed ultrasound system. The patterns observed were similar to those reported by Tuller et al. [J. Exp. Psychol. H.P.P. 8, 460–472 (1982)] for interarticulator timing. Correlations between the duration of a ‘‘period,’’ defined as the interval between the onsets of movements associated with adjacent vowels, and the ‘‘latency,’’ defined as the interval between the beginning of the period and the point in the period at which movement associated with the intervocalic consonant begins, were positive and reliable. The source of this correlation pattern was examined and found not to be due to a scaling of an invariant phase relation but rather due to a main effect for stress on the vowel‐to‐vowel articulatory period combined with an artifactual part–whole correlation within each stress level.

Coordination of lingual and laryngeal gestures in speech

Abstract: Although it is clear that there is extensive cooperation among the articulators in the production of speech, the various ways that articulatory movements can be coupled have yet to be explored in detail. In this paper, we present preliminary findings on the nature of the tongue‐vocal fold linkage in the production of repetitive speechlike sounds. Subjects produced the utterance /kakak/ at both normal and fast speech rates with either the first or the second vowel stressed. The lowering movement of the tongue dorsum and the abduction and adduction gestures of the vocal folds were monitored simultaneously by using a computerized ultrasound system. The kinematic patterns of tongue and vocal fold movement were assessed in terms of linkages between movement amplitudes, durations, maximum velocities, and movement trajectories. Both cooperative and compensatory patterns were examined. In addition, phase relationships between the tongue and vocal folds were evaluated as a function of differences in rate and stress. The discussion focuses on the bases of cooperation in these interarticulator movements.