In 2014 the neuroscientist John O’Keefe won a Nobel Prize for showing that mammals have “place cells” in their brains—an inner mapping system that helps them find their way in the physical world. Now it seems that a particular group of mammals—humans—also have a mapping ability that lets them see themselves in relation to others, thus helping them to navigate in the social world.

It all starts with imitation. In the early 1980s, Andrew Meltzoff, now co-director of the Institute of Learning & Brain Sciences at the University of Washington, found that human babies have an inborn talent for mimicry. Infants just a few days old imitated adults’ facial expressions—and even their finger movements—with surprising accuracy. When Dr. Meltzoff stuck out his tongue or pursed his lips, the newborns did, too.

It’s a handy trick to know that your body and someone else’s have matching moving parts, especially if you’re a newborn who has never looked in a mirror before. But how and why would the human brain be wired to copy what other people do?

Thirty-odd years later, some answers are surfacing. With instruments now available to measure the electrical activity in infants’ brains, Dr. Meltzoff and his colleagues have found that babies have interactive neural maps that match their own bodily sensations to their observations of other people’s movements.

In a paper in the September issue of Trends in Cognitive Sciences, Dr. Meltzoff and Peter Marshall, a professor of psychology at Temple University, discovered that when a 14-month-old baby’s hand was touched, the same region of her brain lighted up as when she saw an adult use his hand to touch something. When the baby watched an adult nudge an object with his foot, there was electrical activity in the region of the brain corresponding to the baby’s perception of her own foot being touched. That study tested 44 14-month-olds, but even much younger babies register a similarity between their own bodies and other people’s, Dr. Meltzoff told me, adding that this recognition may be one root of empathy.

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