Neuroscientists are just beginning to understand the human brain's remarkable capacity to recognise faces

"I am much better at recognising my neighbours' dogs (they have characteristic shapes and colors) than my neighbours themselves," renowned neurologist and prolific writer Oliver Sacks wrote in his book "The Mind's Eye."

Sacks was a prosopagnosic, someone who has difficulties recognising familiar faces — even, sometimes, their own. The condition, prosopagnosia, is a word that combines the Greek words "prosopon," or face, with "agnos," or lack of knowledge.

In the 1990s, researchers identified a region of the brain that is thought to play a key role in our ability to identify a face. They named it the fusiform face area.

Some people who've experienced brain damage to that region suffer from prosopagnosia, but more recently, researchers have diagnosed the condition in people without brain damage as well. This type of prosopagnosia is known as developmental prosopagnosia — its sufferers appear to be born with it. Nevertheless, the deficit doesn't appear to negatively affect other intellectual efforts in those people.

Initially, researchers assumed that there were only two groups of people when it came to facial recognition: prosopagnosics, or people who were face-blind, and everyone else.

They no longer think it's quite that simple.

Now, they're beginning to study people known as "super-recognisers," those with an uncanny ability to remember a face — even that of a practical stranger. One group of researchers has created a preliminary online test that can tell you if you may qualify as a super-recogniser. You can take it right now.

Experts working in the field say these super-recognisers are way ahead of the automated types of facial recognition that companies like Facebook and Microsoft are working on. Eliot Porritt, a detective sergeant with London's Metropolitan Police who leads a group of officers with super-recogniser abilities who are tasked with identifying suspects from grainy surveillance footage, calls automated facial recognition "snake oil." He tells Business Insider that so far, out of every match he's seen one of his officers make, "none of them were suitable for facial recognition software."

Scientists are starting to piece together the puzzle of why the human brain has such a remarkable capacity to recognise faces — and they've only just begun.

The first paper to mention the phrase "super-recogniser" was published in 2009.

In it, Harvard psychologists Ken Nakayama and Richard Russell and University College London cognitive neuroscientist Brad Duchaine outlined the experiences of four people who claimed to have an unusually good ability to recognise faces. In addition, the researchers presented the world's first test designed to identify these so-called super-recognisers, the Cambridge Face Memory Test.

All four subjects in the paper described eerie instances in their past in which they had recognised apparent strangers: family members they hadn't seen for decades or actors they'd glimpsed once in an ad and then seen again in a movie. Each person in the study said that for years they'd felt as if something were wrong with them.

One of the participants, for example, told the researchers she tried to hide her ability and "pretend that I don't remember ... because it seems like I stalk them, or that they mean more to me than they do."

For the first time, the Cambridge test suggested to these people that they weren't alone — that their abilities weren't merely in their head but quantifiable, testable, able to be proved and put down on paper.

What we know — and don't know — about facial recognition

Research suggests that facial super-recognition is fundamentally different from traditional memory in several key ways. First, the ability doesn't appear to be able to be learned or enhanced with training. Second, it appears to have a neurological and structural basis.

In a recent study in the journal PLoS One, for example, researchers studied two so-called memory champions, people who had competed extensively in memory contests and had even been recognised by the Guinness World Book of Records for their memorisation skills. When the researchers studied these people's facial-recognition abilities, however, their results were merely average. In other words, the researchers concluded, something about facial processing was fundamentally different from memory — and it couldn't be learned by any training or class.

Instead, it seemed to be innate.

And if people are born with their facial-recognition abilities, then they most likely have a neurological basis in the brain, researchers say. A super-recogniser, for example, might have a slightly larger fusiform face area than a face-blind person, or the person might show more activity in this area when looking at images of a face.

"Any time there's a psychological difference there has to be a neurological basis," Brad Duchaine, a neurologist at the University College London, told Business Insider. "Just like you'd say, OK, that car is faster than that other car. Is there a difference in their engines? Well yes of course there is."

Still, Duchaine and other researchers lack the data to confirm this. All of the existing studies of super-recognisers are based on very small samples of people — anywhere from just two individuals to a half-dozen people. Several of the researchers have presented their hypotheses about super-recognizers at conferences and presentations, but many of these haven't yet been published in peer-reviewed journals.

In other words, there's still a lot we don't know about super-recognition — and about facial recognition more broadly. And we're just beginning to uncover some of the answers.

See Also:
Researchers trying to figure out how to make you learn like a kid again
Meet the 'super-recognisers,' police officers who never forget a face
3 strategies for remembering everything you learn