Tongue-Jaw Synergy in Vowel Height Production: Evidence from American English

Vowels are traditionally described according to three articulatory dimensions: height, frontness and rounding. Despite the linguistic importance of vowel height in many languages, there is still disagreement about its physiological implementation and its acoustic consequences. One area of controversy is whether the jaw or the tongue dorsum is the main contributor to this linguistic distinction. In American English, height is highly contrastive, distinguishing five front and five back vowels in most dialects. The present paper investigates jaw/tongue synergy in distinguishing /i/ from // as a function of vowel and speaker using two methods of articulatory data collection: x-ray Microbeam (XRMB) and digital ultrasound imaging (HOCUS). For most subjects, both tongue and jaw do contribute to the linguistic distinction between /i/ and //. However, the tongue’s contribution is greater than previously assumed.