[Anticipatory labial coarticulation: an electromyographic study in Afrikaans speaking people].

Anticipatory coarticulation sheds light on the planning of speech by the brain. The aim of this study is to gain information on the temporal extent of anticipatory labial coarticulation, the course of coarticulation for utterances consisting of two rounded vowels separated by an intervening consonant without rounding specification and lastly the effect of word boundaries on the onset of coarticulation in normal Afrikaans speaking adults. The method consisted of the recording of electromiographic (EMG) activity from Musculus Orbicularis Oris using a bipolar concentric needle electrode. The results suggested that anticipatory coarticulation is demonstrated by Afrikaans speaking individuals and that the onset of liprounding for a rounded vowel commenced earlier when the duration of the nonlabial consonantal string preceding the rounded vowel increased. During the investigation of anticipatory labial coarticulation in utterances consisting of two rounded vowels separated by a nonlabial consonant, it was found that two peaks in EMG activity with a pronounced decrease in activity between the peaks occurred. Lastly it was found that anticipatory coarticulation can occur across word boundaries. The results are discussed in relation to different theoretical models of speech production which have been proposed to account for the phenomenon of anticipatory labial coarticulation.