How We Learn To See Faces

Virginia Hughes in National Geographic:

Two eyes, aligned horizontally, above a nose, above a mouth. These are the basic elements of a face, as your brain knows quite well. Within about 200 milliseconds of seeing a picture, the brain can decide whether it’s a face or some other object. It can detect subtle differences between faces, too — walking around at my family reunion, for example, many faces look similar, and yet I can easily distinguish Sue from Ann from Pam.

Our fascination with faces exists, to some extent, on the day we’re born. Studies of newborn babies have shown that they prefer to look at face-like pictures. A 1999 studyshowed, for example, that babies prefer a crude drawing of a lightbulb “head” with squares for its eyes and nose compared with the same drawing with the nose above the eyes. “I believe the youngest we tested was seven minutes old,” says Cathy Mondloch, professor of psychology at Brock University in Ontario, who worked on that study. “So it’s there right from the get-go.”

These innate predilections for faces change and intensify over the first year of life (and after that, too) as we encounter more and more faces and learn to rely on the emotional and social information they convey. Scientists have studied this process by looking mostly at babies’ abilities as they age. But how, exactly, our brains develop facial expertise — that is, how it is encoded in neurons and circuits — is in large part a mystery.

Two new studies tried to get at this brain biology with the help of a rare group of participants: children who were born with dense cataracts in their eyes, preventing them from receiving early visual input, and who then, years later, underwent corrective surgery.

More here.