Prespeech tongue posture reflects upcoming speech motor demands: Evidence from ultrasound and electromagnetic articulography

Speakers maintain distinct postures of the vocal tract in between utterances, however, it remains unclear to what degree these postures are influenced by upcoming motor demands of speech movements. We report two experiments assessing whether prespeech tongue postures changed depending on the motor demands of upcoming speech sounds. First, we employed EMA on the Haskins Production Rate Comparison database, and found that tongue positions between 200 and 100ms reflected the height and backness of the upcoming vowel onset. Next, we used ultrasound imaging to assess the timecourse of postural change in between utterances, and found that interspeech rest postures were influenced by the upcoming vowel much earlier, with task-specificity of the posture increasing further as the onset approached. Qualtitatively, we observe that task-specific properties are overlaid on top of neutral postural substrates such as the clinical resting position. These results demonstrate that pre-speech postures account for upcoming motor demands, supporting previous observations of task-specificity in prespeech posture. These results also identify further commonalities between postural control in gross and fine motor skills.