Effects of contrastive emphasis on jaw opening.

This paper examines the effect of contrastive emphasis on the amount of vertical jaw displacement, as measured from X-ray microbeam data, for 3 American English speakers. Jaw opening in short utterances with one word emphasized (in initial, middle, and final positions) was compared with that of similar utterances with no words emphasized. The results suggest that emphasis involves not only a significant increase in jaw opening on the word emphasized but also possibly a reduction of jaw opening on the word following emphasis. Emphasis in addition may affect the amount of jaw opening of the utterance as a whole, in terms of a decrement in jaw opening on all the remaining words in the utterance following the emphasized word. The relationship between jaw opening and hierarchical levels of prosodic structure is tentatively discussed.