Innate Imitation of Facial Expressions by Newborn Monkeys

Almost 30 years ago, Meltzoff and coworkers reported that 2- to 3-wk-old human infants responded with corresponding matching behaviors to specific human facial gestures, such as mouth opening, tongue protrusion, and lip protrusion. We are born with a computational model that transforms visual information into motor commands, a phenomenal connection between self and others exists from birth. This innate link brings us experientially into a world of others. There seems to be a clear evolutionary rationale for this: in highly social primates the imitation of affiliative and other facial gestures could be a basis of bonding to caretakers and fine tuning complex social interactions. (See my Feb. 10 post on the mirror system of neurons that might underlie this behavior).

The evolutionary origins of this mirroring behavior may extend further back that we have thought. The capacity of neonates to imitate adult facial movements has been thought to be limited to humans and perhaps the ape lineage. Now Ferrari et al report the behavioral responses of infant rhesus macaques (Macaca mulatta) to human facial and hand gestures: lip smacking, tongue protrusion, mouth opening, hand opening, and opening and closing of eyes.

Here are pictures they provide of monkey infants tested 1-3 days after birth, imitating mouth opening and tongue protrusion. By day 7 the imitation behavior had largely disappeared, unlike human and chimpanzee behaviors. This might be because these monkeys mature very rapidly, and by one week may already be leaving their mothers for short periods of time.