Anticipatory labial coarticulation: experimental, biological, and linguistic variables.

The research reported here represents an attempt to resolve the differences between two views of anticipatory labial coarticulation. One of these views contends that a speaker begins labial movement toward a rounded vowel in direct relation to the amount of time available, while the other view posits an onset of movement that is temporally locked to the rounded vowel. Electromyographic signals were sampled from four muscles associated with labial movement while, simultaneously, movements of the upper lip in the anterior-posterior and vertical dimensions were recorded. Four native speakers of American English and five native speakers of Swedish served as subjects. Results suggested that (1) there are a number of purely biological and experimental variables which can intrude upon research of this type, and (2) there are also language-specific differences in the production of rounded vowels which suggest that Swedish and American English speakers have learned different motor-programming goals. This second observation is discussed in terms of acoustic/perceptual needs of the speakers of a language.