Right visual field advantage for perceived contrast: correlation with an auditory bias and handedness

Studies have suggested that supramodal attentional resources are biased rightward due to asymmetric spatial fields of the two hemispheres. This bias has been observed especially in right-handed subjects. We presented left and right-handed subjects with brief uniform grey visual stimuli in either the left or right visual hemifield. Consistent with the proposed asymmetry in attentional resources, right-handed subjects estimated right hemifield targets as having a higher contrast than physically identical stimuli presented in the left hemifield. Left-handed participants did not show a systematic rightward or leftward bias. However, the group of left-handed participants also took part in a dichotic listening experiment whose results showed that visual bias score correlated positively with ear-advantage in dichotic listening. Our results are consistent with the view that supramodal processing resources are biased towards the right hemispace, and that this bias is influenced by handedness.