Interhemispheric difference in emotional response without awareness

To investigate interhemispheric differences concerning unconscious human emotional responses processed, we measured human skin conductance responses (SCRs) to masked (unseen) emotional stimuli presented to left or right visual fields. Backward masking was used to preclude conscious processing of emotional stimuli. Masked negative or neutral emotional pictures from the International Affective Picture System (IAPS) were presented to 11 right-handed male volunteers. Mean SCR for negative emotional stimuli presented to the left visual field was significantly greater than mean SCRs for negative emotional stimuli to the right visual field and for neutral stimuli to the left or right visual fields. Thus, the right rather than the left hemisphere appears to respond to preattentive negative emotional stimuli.