Oral asymmetries during verbal and non-verbal movements of the mouth

Asymmetries in the amplitude and velocity of oral movements were studied in 24 right-handed subjects as they produced either syllables or non-verbal movements of the mouth. Single-frame analysis of the videotaped mouth movements revealed that the right side of the mouth opened wider and faster than the left for both verbal and non-verbal movements. Moreover, the size of the right bias increased as a function of the complexity of required movements. In addition, movements embedded within a series showed a greater right bias than movements at the beginning of a series. On the whole, females exhibited larger asymmetries than males. These results provide support for the suggestion that the left hemisphere plays an important role in the control of complex motor behaviour.