Coordination of articulatory movements in multi-gesture sequences

Articulatory Phonology claims that phonological structure is instantiated in the acoustic speech signal by the precise and consistent coordination of movements by otherwise independent articulatory structures (i.e., lips, tongue, and jaw). However, this theory does not provide firm evidence showing what aspects of those movements are coordinated reliably to achieve linguistically relevant task goals. In this study we explored how consonant identity may be instantiated by three candidate movement epochs involving three articulators: movement onsets, movement offsets, and peak displacements. To this end, young adults were recorded using electromagnetic articulography producing vowel-consonant-vowel sequences with varied vowels (/ɑ/-/ɛ/) and consonants (alveolar or labial stops), across voicing, rate and stress conditions. Coordination between both jaw and tongue tip (alveolar stops) and jaw and lip (labial stops) were examined. Across voicing, rate and stress conditions, the relative timing of movement onsets for jaw and the other articulator (tongue tip or lip) were consistently maintained; timing of the other two events were not consistently maintained. These findings suggest that across syllable-sized stretches of speech, consonant identity arises from rigid control of inter-articulator movement onsets, whereas later articulatory kinematic trajectories are flexibly controlled to meet evolving task demands.