Sex differences in oral asymmetries during wordrepetition

During speech production the right side of the mouth is opened to a larger degree in most people. This facial asymmetry is thought to be related to a left hemisphere dominance in language processing and/or motor programming. We investigated asymmetrical lip separations during discrete or serial word productions in right handed persons. The results revealed a right sided li p separation bias in both genders during discrete word production in which the words had to be uttered once. As soon as the words had to be produced c ontinuously, however, a clear sex difference appeared with males having the usual right bias but females now showing no clear asymmetry, with a tenden cy for larger lip separations on the left side. These results suggest the e xistence of two separate neural systems from which one controls the discret e task and which is left hemisphere dominant in both genders. The other is probably involved in serial word productions and shows a sex difference wit h regard to its asymmetry pattern. (C) 1998 Elsevier Science Ltd. All right s reserved.