The tongue is a deformable object, and moves by compressing or expanding local functional segments. For any single phoneme, these functional tongue segments may move in similar or opposite directions, and may reach target maximum synchronously or not. This paper will discuss the independence of five proposed segments in the production of speech. Three studies used ultrasound and tagged Cine-MRI to explore the independence of the tongue segments. High correlations between tongue segments would suggest passive biomechanical constraints and low correlations would suggest active independent control. Both physiological and higher level linguistic constraints were seen in the correlation patterns. Physiological constraints were supported by high correlations between adjacent segments (positive) and distant segments (negative). Linguistic constraints were supported by segmental correlations that changed with the phonemic content of the task.