Human and ape newborns learn by imitating the behavior of adults. Researchers have found that rhesus macaque monkeys learn this way too.
Since newborns cannot see their own faces, they rely on watching adults to learn facial expressions, and mimicry is thought to be crucial to the development of a mother-infant relationship.
Particular brain cells – called “mirror neurons” – fire in a human infant when it watches an adult expression and copies it. Similar mirror neurons "light up" when rhesus monkeys watch another animal perform an action and when they copy that action.