Human subjects were asked to perform a task while recordings were made of the electrical activity of the right masseter muscle. The task apparatus consisted of a series of lamps illuminated in random order, and a button panel. The subjects were asked to press the buttons to correspond with the lamps illuminated. Recordings made from the muscle during this task showed an increase in electrical activity. The magnitude of this increase was related to the number of errors made by the subject. Muscle activity with similar characteristics has been shown by earlier workers to occur elsewhere in the body. It is suggested that such psychogenic activity in the masticatory muscles could affect mandibular posture, and the findings reported are discussed in relation to the current hypothesis of the control of mandibular posture. © 1969.
