Effect of verbal interference and response hand on hemisphere asymmetries in sad facial expression processing.

A growing amount of evidence highlights a role for the left hemisphere in negative facial expression processing. The present study investigated the extent to which language contributes to this left hemisphere involvement by comparing performance during an emotion detection task presented to the left and right hemispheres using divided visual field under conditions of verbal interference (covertly rehearsing a 6-digit string for a subsequent memory) and no interference. Participants were college undergraduates with no known neurological or psychiatric conditions. Half used their right hand to respond and half used their left. In line with the hypothesis that language contributes to left hemisphere involvement in negative expression processing, participants who used their right hand to respond were more accurate with sad facial expressions when they were presented to the left hemisphere than the right during the no interference condition, but this left-hemisphere advantage disappeared during the verbal interference condition. Contrary to the hypothesis, participants who used their left hand to respond were more accurate with sad facial expressions when they were presented to the right hemisphere than when they were presented to the left, and this right-hemisphere advantage did not differ significantly between interference groups. Results highlight the influence of language as well as response hand on hemisphere asymmetries in facial expression processing and point towards areas for future research.