Ultrasound imaging and theories of tongue root phenomena in African languages

Abstract

During the past decade, ultrasound (US) technology has played an important role in the development of phonetic and phonological theory, with much of the US research focussing on Indo-European languages. We explore the role of lingual ultrasound imaging in the documentation of African languages. We focus on three tongue root (TR) related phenomena: tongue-root harmony, click induced vowel retraction, and labial-velar fronting, and demonstrate how lingual US studies contribute to the development of theories of the phonetics / phonology interface. In Dagbani, the phonologically dominant [+ATR] feature corresponds to an anterior position of the TR relative to the neutral position. Click data from Mangetti Dune !Xung, henceforth !Xung, show that TR retraction is part of the rarefaction gesture for two out of four clicks. We argue that phonetic TR retraction directly implies the presence of an [RTR] feature, which explains the patterning of clicks in the Back Vowel Constraint (BVC), a constraint ruling out the occurrence of [RTR] clicks with front vowels. We show that tongue dorsum (TD) / TR retraction captures the Dagbani restriction against labial-velars with front vowels. This raises the possibility that labial-velars may have the feature [RTR] which is lost in the front vowel context. The !Xung and Dagbani US data show that what might be considered inert articulatory movements may be linked to active or enhancing feature specifications. Ultrasound imaging, which allows us to clearly visualize the position of the TR in a non-invasive way, contributes to a theory of direct mapping of tongue root phenomena in African languages.