How do we recognize faces?

By Casey Frye, CCNN Writer

faces
Our brains are wired for facial recognition. Take that Google Glass!

You know what I realized today? Our faces are basically made up of two eyes, two cheeks, one mouth, and a nose. Pretty simple stuff, right? Yet tiny little changes in these features make us look totally different from one another.

If you think about how many people you actually know – like family, friends, teachers, peers, and even celebrities – it’s incredible that we can tell individuals apart at all! In fact, the way the brain recognizes faces has been a mystery to scientists.  Now, however, a recent study has found some clues that hint at how it’s possible.

In order to run their study, researchers used a rare group of participants: 11 children who were born with cataracts – or cloudy areas on the eye’s lens that block vision – and got corrective surgery a few years after birth. These children could see just fine, except they had a bit of trouble with distinguishing faces.

That’s not to say the children didn’t know what a face looked like. When they were presented with images of a face and and an object – such as a house – the participants could point out which was which easily. In fact, when the volunteers were shown two pictures of an identical person with only one difference, such as eye color, they could identify what changed. When it came time to view pictures of two different people, however, the children had a hard time telling one person from another.

This is really interesting because normally, humans can identify the differences in less than a second. “We know they are able to categorize faces and other objects, and even distinguish between two faces, but only if they see them from the same view,” says Brigitte Röder, professor of neuropsychology at the University of Hamburg in Germany. “If the perspective changes, or lighting of pictures changes, or the emotional expression, they have a hard time.” Wow, can you imagine not recognizing a friend if you saw them from the side, or if they had a smile on their face?

After Röder and her research team scanned the children’s brains with an electroencephalogram (EEG) – which measures brain waves – the scientists observed some pretty interesting data. Usually, there is a special brain wave called N170 that shows up only after someone has seen a face. In the participants, though, the N170 popped up with any visual stimulus, whether it was a face or a house.

With this data in hand, the researchers are now suggesting there is a limited amount of time known as the “sensitive period.” In this short window of time, an individual’s brain only has two months to learn how to recognize faces! And it’s not just looking at two dots and a smile. In fact, the brain has to acquire a fine set of skills to distinguish tiny differences from one face to another.

“Just two months seems to permanently change the brain’s response to faces, and cause permanent impairments in some face processing skills,” said Cathy Mondloch, professor of psychology at Brock University in Ontario who conducted a similar study published this month.

Featured image courtesy of Stephen L. Harlow on Flickr. Image of multiple faces courtesy of Denise Krebs on Flickr.