from NewScientist.com

Pier Ferrari at the University of Parma, Italy, and colleagues tested 21 newborn macaques by holding each in front of a researcher who made various facial expressions.

At one day old, none of the infants showed any imitation. By day three, however, infants started to copy the researchers’ expressions, including tongue protrusions, mouth opening and lip smacking – all typical macaque expressions.

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{I'm not sure what this footage proves, but it sure is cute!}