Coordination and coarticulation in speech production.

In this article, we consider the concepts of coordination and coarticulation in speech production in the context of a task-dynamic model. Coordination reflects the transient establishment of constrained relationships among articulators that jointly produce linguistically significant actions of the vocal tract--that is phonetic gestures--in a flexible, context-sensitive manner. We ascribe the need for these constraints in part to the requirement of coarticulatory overlap in speech production. Coarticulation reflects temporally staggered activation of coordinative constraints for different phonetic gestures. We suggest that the anticipatory coarticulatory field for a gesture is more limited than look-ahead models have suggested, consistent with the idea that anticipatory coarticulation is the onset of activation of coordinative constraints for a forthcoming gesture. Finally, we ascribe much of the context-sensitivity in the anticipatory or carryover fields of a gesture (variation due to "coarticulation resistance") to low-level (below the speech plan) interactions among the coordinative constraints for temporally overlapping gestures.