Triggering and spreading of lateral tongue posture

Abstract

Lateral bracing is a tongue posture that is pervasively maintained during speech across languages (Liu et al., in press), released only for a few English sounds ([l] and occasional low vowels; Gick et al., 2017). While bracing is required for many (e.g., coronal) sounds, it is unclear why bracing is maintained during non-lingual sounds (e.g., labial/glottal consonants). Specifically, it is unknown whether bracing is maintained during non-lingual sounds because it is a pervasive default posture for speech (i.e., turned “on” unless actively suppressed, e.g., for /l/) or whether an unbraced posture can be maintained during extended periods. We collected coronal cross-section ultrasound imaging of the dorsal tongue while participants said “hubba-bubba” (a four-syllable sequence of non-lingual consonants and low vowels) in two contexts: surrounded by mandatorily braced sounds (e.g., /s/) versus unbraced sounds (e.g., /l/). Preliminary results show that the lateral tongue stayed in a lowered position throughout “hubba-bubba” when surrounded by unbraced sounds compared to braced sounds. Results suggest the lateral tongue may be held in one of at least two distinct postures whose activation is controlled by “trigger” events. [Work supported by NIH and NSERC.]