Exploring the Connection Between Orofacial Myofunctional Disorder, Speech Errors of /s/ and /z/, and Auditory Perception Skills

Orofacial Myofunctional Disorder (OMD) is defined as “abnormal movement patterns of the face and mouth” by ASHA (2023). OMD leads to anterior carriage of the tongue, open mouth posture, mouth breathing, and tongue thrust swallow. Dentalization speech errors of /s/ and /z/ are also known to be caused by low and forward position of the tongue (Wadsworth, Maui, & Stevens, 1998). This study used the OMES-E protocol to identify 10 out of 40 participants with OMD. A cut-off below 80% accuracy for the production of /s/ and /z/ sounds classified 6 out of 40 participants with speech errors. Then, a correlation was run between speech score and OMD classification; it was not significant. This raises the question, why do some people with OMD have moderate to severe speech errors of /s/ and /z/, and some who have OMD do not? This study aims to explore this question beyond the motor modality. Using an auditory perception paradigm, the first and second formants of the vowel /ɛ/ were shifted to approximate /æ/. The participant’s responses and compensations to these shifts were recorded in real time. Results of this perceptual test could suggest that perceptual/compensatory differences may explain why some people in the OMD population have speech errors and some do not.