An informational account of anticipatory coarticulation – theoretical considerations and empirical plausibility
Résumé
In speech, the realization of a phoneme is influenced by its preceding and forthcoming neighbors, a phenomenon called coarticulation. While influences from past actions (carryover coarticulation) can be explained by a combination of physical causalities and motor planning, influences from future action goals can only be fully explained by active anticipatory processes in speech motor control. Current modeling accounts view coarticulation as a side effect of efficiency objectives of control or properties of the planning algorithm.Here, we propose that anticipatory coarticulation provides prospective sensory cues usable for feedback-dependent speech control. To support this notion, we characterized the dynamics of carryover and anticipatory coarticulation in three French speakers in both acoustic and articulator data as measured by Electromagnetic Articulography using General Additive Models. Our data show that anticipatory coarticulation effects dominate over carryover coarticulation effects and allow to reliably differentiate between upcoming phonemes at least 200 ms before the canonical phoneme onset.These findings are compatible with an anticipatory feedback-dependent control strategy, as sensory information about future actions is available early enough to influence ongoing actions in spite of sensorimotor delays. Such considerations weaken the necessity for fully fledged internal predictive forward models for the control of fast actions.