RIGHT-HEMISPHERE DOMINANCE FOR THE PRODUCTION OF FACIAL EXPRESSION INMONKEYS

In humans, the left side of the face (right hemisphere of the brain) i s dominant in emotional expression. In rhesus monkeys, the left side o f the face begins to display facial expression earlier than the right side and is more expressive. Humans perceive rhesus chimeras created b y pairing the left half of the face with its mirror-reversed duplicate as more expressive than chimeras created by right-right pairings. Tha t the right hemisphere determines facial expression, and the left hemi sphere processes species-typical vocal signals, suggests that human an d nonhuman primates exhibit the same pattern of brain asymmetry for co mmunication.