Response by Dr. Robert M. Mason, DMD, PhD
What is the functional application of knowing that a child is right or left tongued? Nothing at all. This information simply changes the incorrect view that everyone seems to have of how a swallow takes place, which is envisioned by most as involving a deep groove in the middle of the tongue that a bolus of food, resembling a bowling ball, rolls down on its way into the pharynx. The sidedness of posterior tongue functions more fully explains the phenomenon of swallowing and the asymmetrical nature of it, especially at the posterior portion of the tongue. Food is usually chewed on one side or the other, and is then moved by the tongue from where the food is found, (and not necessarily to the midline of the tongue) so a swallow should be expected to involve an asymmetrical movement pattern of the tongue — at least the lateral/posterior portion of the tongue that acts as the hinge to control the tongue tip during both a swallow and some speech sounds such as /s/. For /s/, one side of the posterior tongue contacts the upper molars or palate next to the molars to provide stability for the actions intended for the tongue tip – (the back of the tongue acting as a hinge to control the vertical movements of the tongue tip) but this doesn’t have to happen all of the time; however, the normal description of the activities of the lateral portions of the posterior tongue should include the concept of asymmetrical movements, with one side elevating much higher than the other side. Is it possible to determine if a child is right or left tongued without a pressure transducer study? Probably, but I can’t think of any way off hand, however, this could be of some significance for some patients with neuromotor disorders. So far, it only helps to clear up misconceptions of what a swallow really looks like, whether normal or abnormal.