Hemispheric asymmetries in stutterers: disorder severity and neuroticism?

This study tests the hypothesis that there is atypical brain asymmetry in stuttering children. In particular the association of both severity of stuttering and neuroticism with cerebral laterality in perception of visuospatial material is tested. Subjects were asked to recognize faces presented laterally in the left or right visual field and point to the exposed stimuli on response cards containing three different faces. Recognition errors committed in the left and right field presentations were analyzed. In fluent speakers and in moderately neurotic stutterers, fewer errors were found for the right hemisphere independently of their neuroticism score; in contrast, stutterers with a high neuroticism score showed fewer errors for the left hemisphere. The latter was true regardless of severity of stuttering. The study suggests a close link between atypical hemispheric dominance in the face recognition test and the emotional state in stutterers as defined by their neuroticism score. This characteristic may be related to the negative emotional reactions demonstrated relatively often by stuttering individuals. In highly neurotic stutterers, the negative affective states might be associated with disturbances of right hemisphere functioning and related to an atypical asymmetry pattern in the processing of right-hemispheric stimuli. These results illustrate the importance of controlling for subject-related factors while conducting and interpreting investigations on stutterers.