Visual and Auditory Language Processing Asymmetries: Influences of Handedness, Familial Sinistrality, and Sex

Abstract

The relationships of familial sinistrality (FS), subject sex, and degree of left-or right-handedness to hemispheric efficiency differences in visual and auditory processing of verbal stimuli were studied. A strong effect of FS on visual processing asymmetry, replicating previous findings in our laboratory, obtained for left-handed subjects. The FS + left-handers showed the right visual field recognition superiority indicative of relative left hemisphere dominance while the FS - subjects showed no evidence of hemispheric asymmetry. A significant sex effect occurred among the right-handed subjects, with females showing evidence of left hemispheric superiority and males failing to show any significant hemispheric asymmetry. All right-handed sex-FS subgroups showed evidence of left hemisphere superiority for auditory verbal processing, but among the left-handed subjects only the FS + females and the FS - males showed significant evidence of left hemisphere superiority. The FS - females' performance was quite heterogenous but with a marked tendency toward left hemisphere superiority, while the FS + males showed a very clear absence of hemispheric asymmetry for processing the auditory-verbal stimuli. Measures of degree of left - or right-handedness consistently failed to relate to cerebral processing laterality measures. The relationship of present results to other findings was discussed and methodological problems were considered. It was concluded that both FS and sex may moderate the degree of “cerebral dominance” for language processing, and that failures to adequately assess these variables may underlie much of the inconsistency of findings in the area.