Cross-modal asymmetries in perception related to asymmetry in cerebral function

Abstract

Cross-modal correlations between left-right asymmetry on the Dichotic Listening (D-L) test and a visual half-field ((VHF) test were obtained for 30 right-handed subjects with no family history of left-handedness, 30 right handed subjects with a positive family history of left-handedness and 30 left-handed subjects. Both groups of right-handed subjects demonstrated significant cross-modal correlations between the D-L (auditory) asymmetry and the VHF (visual) asymmetry. The left-handed subjects displayed no correlation between D-L and VHF asymmetries. This suggests a dissociation between auditory and visual laterality in left-handers. Differences between this finding and two previous studies which found no cross-modal asymmetry for right-or-left-handers are discussed. The visual half-field test utilized in this experiment controlled fixation by presenting digits sequentially at fixation, while simultaneously presenting other digits to either the right or left VHF. This procedure minimizes the effect of directional scanning on VHF asymmetry. The reliability of the D-L and VHF asymmetries was also computed. The D-L asymmetry proved to be highly reliable ( r = 0.86), while the VHF asymmetry was somewhat less reliable ( r = 0.46). The asymmetry on both tests was attributed to asymmetry of cerebral function.