Control parameters for coordinative structures in speech production

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In skilled speech production, sets of articulators work cooperatively to achieve task-specific movement goals, despite rampant contextual variation. Efforts to understand these functional units, termed coordinative structures, have focused on identifying the essential control parameters responsible for allowing articulators to achieve these goals, with some research focusing on temporal parameters (relative timing of movements) and other research focusing on spatiotemporal parameters (phase angle of movement onset for one articulator, relative to another). Here, we compared findings across three recent studies where both types of control parameters were investigated, using electromagnetic articulography recordings. In each study, talkers produced VCV utterances, with alternative V (/ɑ/−/ɛ/) and C (/t/−/d/ or /p/−/ b/), across variation in rate (fast–slow) and stress (first syllable stressed–unstressed). Two measures were obtained: (i) the timing of tongue-tip or lower-lip raising onset for intervocalic C, relative to jaw opening–closing cycles, and (ii) the angle of tongue-tip or lower-lip raising onset, relative to the jaw phase plane. All three studies showed that the correlations of tongue-tip/lower-lip movement onset latencies and jaw opening-closing cycle durations were stronger and more reliable than the correlations of tongue-tip/lower-lip phase angles and jaw opening-closing cycle durations, demonstrating that timing is the critical control parameter.