Mouth asymmetry, dichotic ear advantage and tachistoscopic visual field advantage as measures of language lateralization.

Clinical evidence suggests that speech expression, speech comprehension and reading have distinct anatomical representations and that these functions may have differential degrees of lateralization. Experimental measures sensitive to the lateralization of these functions may be, respectively, mouth asymmetry, dichotic listening and visual field advantage. These measures, individually, showed relatively low success in estimating overall "language dominance" and had low intercorrelations. A composite measure was more successful. Language lateralization may not be unitary, and even if it is, a composite of several distinct measures may be necessary to index it.