Here is a great story: human imitation has been known to be present in newborns, supporting a notion of the human race being predisposed to social interaction. However, an obvious question of whether this is also the case in non-human primates below our closest evolutionary relatives has not been asked. Until now. In an excellent study by Pier Ferrari and colleagues in PLoS Biology, imitation of facial expression is demonstrated in neonatal monkeys (that disappeared after approx. 7 days).
From ScienceDaily we can read:
Ferrari et al. tested 21 baby rhesus monkeys’ response to various experimental conditions at different ages (one, three, seven, and 14 days old). Infants were held in front of a researcher who began with a passive expression (the baseline condition) and then made one of several gestures, including tongue protrusion, mouth opening, lip smacking, and hand opening.
Day-old infants rarely displayed mouth opening behavior, but smacked their lips frequently. When experimenters performed the mouth opening gesture, infants responded with increased lip smacking but did not increase any other behavior. None of the other stimuli produced significant responses. But by day 3, matched behaviors emerged: infants stuck out their tongues far more often in response to researchers’ tongue protrusions compared with control conditions, and smacked their lips far more often while watching researchers smacking theirs. By day 7, the monkeys tended to decrease lip smacking when humans performed the gesture, and by two weeks, all imitative behavior stopped.
Here is an example from the article:
And from the abstract:
Our findings provide a quantitative description of neonatal imitation in a nonhuman primate species and suggest that these imitative capacities, contrary to what was previously thought, are not unique to the ape and human lineage. We suggest that their evolutionary origins may be traced to affiliative gestures with communicative functions.
UPDATE: Jown Hawkes has an in-depth presentation and discussion of this study.