Intragestural dynamics of multiple prosodic boundaries

Abstract Recent work has demonstrated that temporal lengthening of articulatory gestures adjacent to an intonational phrase boundary can be interpreted as resulting from a lower underlying gestural stiffness. Magnetometer data from three subjects were examined to determine whether multiple levels of prosodic boundaries can be distinguished in the spatio-temporal patterning of articulation and whether these patterns are consistent with the lowered gestural stiffness account. Eighty tokens were recorded of a /CVCV#CVCV/ sequence with five differing boundary conditions intended to elicit multiple prosodic boundaries. Magnitude and duration of each consonantal closing and opening gesture, and the temporal latency between consonants were determined. Three levels of interconsonant latency in the /CV#CV/ portion of the utterance can be statistically differentiated. These differences result from lengthening of postboundary closing movements and, to a lesser extent, the pre-boundary opening movements. Concomitant spatial changes are discussed. The kinematic data are used to model the intragestural dynamics of boundary-adjacent lengthening. This modeling suggests that although lowered gestural stiffness is the main source of lengthening, another parameter—a rise-time for gestural activation—is also necessary. Speaker-specific differences in dynamics are accounted for by corresponding differences in the manner in which rise-time varies with stiffness.