Assimilation or coarticulation? Evidence from the coordination of tongue gestures for the palatalization of Bulgarian alveolar stops.

Three issues are considered in this report —are assimilation and coarticulation the same process or different, are they achieved by feature spreading or by coproduction, and what level or levels of neuromotor planning or production do they represent? Tongue gestures analysed from an X-ray motion film of Bulgarian speech are presented as examples of what the tongue is made to do in speech and of how those gestures are co-ordinated with other articulator gestures, in particular for the palatalization of apico-alveolar stops. The gestures involved in this assimilation are initiated earlier, or are held longer, than in nonassimilated situations. The revision of gesture timing in relation to adjacent activity indicates that assimilation is preplanned and does not reflect coarticulation or the effect of vocal tract biodynamics. Secondly, the gestural programming for this case of palatalization is better described as coproduction than feature spreading. Finally the temporal organization of coarticulation reported here also agrees with that reported previously. In particular, potentially conflicting gestures are not blended but are produced sequentially, which favors the gesture queuing paradigm rather than the tug-of-war paradigm and indicates that coarticulation is also preplanned.