Lateral tongue bracing is a lingual posture in which the sides of the tongue are held against the palate and upper molars, and has been observed cross-linguistically. However, it is unknown whether lateral bracing makes adjustments to external perturbation like other body postures. The present study aims to test the robustness of lateral tongue bracing with three experiments. The first baseline experiment was an analysis of an electropalatogram database and the results showed lateral bracing being continuously maintained. The second experiment applied an external perturbation during speech production. A bite block was held between participants’ teeth while intra-oral video was used to record contact between the sides of the tongue and upper molars during speech. The results indicated that lateral bracing was maintained most of the time during speech. The third experiment included simulations investigating the activation of tongue muscles relevant to lateral bracing at different degrees of jaw opening. The results show that bracing requires higher activation of bracing agonists and lower activation of bracing antagonists as jaw opening increases. Our results suggest that lateral tongue bracing is actively maintained and robust under external perturbation and further indicate it serves as an essential lingual posture during speech production.

Lateral bracing refers to an intentional tongue posture whereby the sides of the tongue make contact with the sides of the palate and the upper molars. While previous research on this topic has focused mostly on English, the present study tests the hypothesis that lateral bracing provides a fundamental postural basis for speech and is present across languages. We predicted that, across multiple languages, the sides of the tongue should be more stable than the center and should stay in a relatively high position in the mouth throughout most of running speech. Using coronal ultrasound imaging, we measured tongue movement produced by speakers (N = 28) of six languages (Akan, Cantonese, English, Korean, Mandarin and Spanish). Across these languages, as predicted, the sides of the tongue throughout running speech were positioned higher in the mouth than the center, and the range of movement of the sides was significantly smaller than that of the center of the tongue. These findings support the view that the sides of the tongue maintain a braced posture across languages while speaking, potentially constituting a universal, rather than language-specific, postural basis for speech.