Syllable structure and stress effects on articulatory coordination

Two experiments are reported, both dealing with syllable affiliation of a consonant. The first experiment extends the work of Tuller and Kelso (1990) and was designed to capture the signatures of loss of stability in a dynamical system (enhanced fluctuations and critical slowing). An Articulograph device (Carstens Medizinelektronik GmbH.) was used to track the movements of the tongue tip, the lower lip, and the jaw in the midsagittal plane while the subjects spoke a VCC word in time to an auditory metronome at a slowly increasing rate. A clear transition occurred in the phonetics (VCC -> CVC) as judged by a phonetically trained listener, and the transition in phonetics corresponded to a change in the relative phase between the tongue tip and the lower lip and between the tongue tip and jaw. The transition was accompanied by both enhanced fluctuations and critical slowing for subjects who complied with the metronome. The second experiment examined syllable affiliation in natural English phrases with contrasting metrical structures. The phonemes /s/, /t/ and /k/, were used, and the tongue tip, tongue blade, and jaw were recorded by the Articulograph device. Consistent relative timing of the consonant movement in relation to vowel movement was observed, thus supporting the position that syllable affiliation is expressed as distinct phase values in natural speech as well as reiterated speech. In addition, the evidence supports the view that the syllable is an organizational unit of speech in English.