You may have mild prosopagnosia

When the ability to recognize faces is lacking

People hooded with protective masks shape the streetscape in times of Corona. It is noticeable again and again how tricky it is to recognize a face under the mask. But even without such an additional challenge, the gray cells in terms of face recognition have to perform amazingly. The face has a complicated three-dimensional shape, and many faces look quite alike. Nonetheless, humans have developed the ability to spot faces quickly, accurately, and with seemingly little effort.

In fact, according to the latest estimates, a person can remember and recognize an average of around 5,000 faces. However, some people would be happy if they could even recognize a few faces. Like the artist Carlotta, the protagonist in the documentary "Lost in Face". Carlotta is one of the 2.5 percent of the population who have massive problems recognizing faces, even if the faces of their acquaintances are concerned. Because Carlotta suffers from facial blindness, also known as prosopagnosia.

How gray cells work

The film was made by the doctor and neuroscientist Valentin Riedl, who is researching the functioning of the human brain at the Rechts der Isar University Hospital in Munich. When he learns in the course of an exhibition by the artist that Carlotta doesn't even recognize her own face and still takes self-portraits of himself, he is gripped by the subject.

But how do gray cells even recognize faces? "Information from the retina is processed in the back of the brain," says Riedl. "On the first level, very simple features such as lines and edges of objects are processed in the visual cortex in the occipital lobe." Then the information is passed on in the brain, colors are recognized and gradually more complex objects are processed. One of these more complex objects is the face. "As soon as an object has a circular shape like a smiley face, with a line and two points like the mouth and nose, the fusiform facial area in the fusiform gyrus, the facial region in the brain, starts."

Carlotta can tell the faces of animals apart. But she does not notice when she sees a monkey and not a person in a picture. "This suggests that the fusiform facial area really only responds to a facial structure like that of primates," says Riedl. So on a circular face shape with the eyes in front. "If, on the other hand, the face is elongated and the eyes are on the side, as is the case with horses, for example, other areas of the brain react." That's why Carlotta can probably tell the faces of animals other than monkeys apart, because the fusiform facial area is not in demand here.

Visual processing

However, not only the fusiform facial area, but an entire network is involved in facial recognition, adds neurologist Eugen Trinka. He is head of the University Clinic for Neurology at the Christian Doppler Clinic in Salzburg. There are fiber connections from the occipital lobe - which, as mentioned, shows visual information from the eyes - to the temporal lobe. This is the so-called "what path". It is used to recognize an object or a face. "On the what path, the visual information is compared with the memory content, ie it is checked whether the currently perceived face is known," says Trinka. And a study by Alexander Cohen from Boston Children's Hospital and his colleagues from 2019 suggests: In addition to the what path on the right side of the brain, the left frontal lobe also plays an important role in this network - even if its exact role is still unclear is.

Because there are different actors in the brain in facial recognition, people struggle with different forms of facial blindness depending on the location of the brain damage from an accident or a stroke. With one variant, those affected cannot see any individual parts of the face because the facial area in the fusiform gyrus is damaged. "With the other variant, those affected can recognize individual parts of the face - for example, detect that a person has a large or small nose," says Trinka. "However, you cannot assign such characteristics to a person because the temporal lobe is damaged, which makes a comparison with already known faces."

In the genes

In addition to these cases of acquired facial blindness, there is also a congenital variant that has a genetic background. "It is likely to be inherited as an autosomal dominant trait. So there are carriers of this trait in every generation," says Trinka. Valentin Riedl is convinced that there are also minor cases of facial blindness. "While I was making the documentary, friends told me that they had difficulty telling different blonde women in a film, for example." Riedl himself often does not recognize people he has not seen for a long time. "Then I am more likely to be addressed by them." The ability to recognize faces is a continuum.

At one extreme are people with severe facial blindness. At the other extreme are so-called super recognizers. "You also recognize a supermarket cashier whom you only saw ten years ago," said Riedl. In order to compensate for their deficits, sufferers with severe facial blindness resort to circumvention strategies. You recognize people in other ways: through posture, movement, clothing and language. Eugen Trinka is familiar with this from personal experience. "Since I'm very short-sighted, I don't recognize people from a distance by their face. But they can be easily identified by their posture."

Compensate for the deficit

The artist Carlotta herself uses a traditional type of lithography for her self-portraits. In the dark, she feels her face with one hand and transfers what she feels to the paper. There are no real therapeutic options in the case of severe facial blindness. Prosopagnosia is also not considered a disease, but merely a cognitive disorder. "People with congenital facial blindness are considered to be well integrated," says Trinka.

"But for me the question arises as to whether the people can really compensate for their deficits one hundred percent. Or whether they don't suffer from social restrictions after all." Especially if you could recognize facial blindness in a child, something could be done by training him to recognize faces. "One should do more research in this direction." (Christian Wolf, January 16, 2021)