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.