Face blindness, officially called prosopagnosia, is the inability to identify people based on their face. People with this condition don’t have a vision problem - their eyes work just fine. They have a brain problem - when their brain tries to process the visual image of a face and match it to a specific, known identity, they struggle. They may be able to look at four different face images and identify how they are similar and how they are different - “these two have blond hair” or “that face has brown eyes”. But they can’t look at a face and identify the person, even if they have known the person for some time. It raises an interesting question - when you look at a friend or family member, what is it you are doing to identify them? How do you do it? We start to develop the ability to recognize faces as soon as we are born, but we don’t often think about how it works.

There are two varieties of prosopagnosia. When a person gets prosopagnosia after a brain injury, such as a stroke or head trauma, it is called acquired prosopagnosia. This form can be very severe and is also fairly rare. In extreme cases, a person might not be able to recognize their own family. However, more people than previously believed have developmental prosopagnosia, which is prosopagnosia without brain injury. This condition is less severe, and people may eventually learn to identify people by their faces, it just takes much longer than normal. It’s possible that recognizing people is a skill that falls on a bell curve, and some people just need a lot more practice than others.

In a recent interview, the actor Brad Pitt disclosed that he suffers from prosopagnosia. Although Mr. Pitt, 58, has never had a formal diagnosis, he admitted in a GQ interview that he had had trouble recognizing people’s features for years.

He admitted to Esquire in 2013 that his difficulty recognizing faces had gotten so bad that he frequently felt the need to isolate himself. He explained, “That’s why I stay at home.”

Think about how your life would be different if you couldn’t easily identify the people you know. A person with prosopagnosia may avoid social settings and grow to fear them intensely, a condition known as a social anxiety disorder. Additionally, they could struggle in their profession or have issues with relationships. Depression-like emotions are frequent. Some prosopagnosia sufferers are unable to identify specific facial expressions, determine a person’s age or gender, or follow their gaze.

Others might not even be able to identify their face in pictures or in the mirror. A person’s capacity to recognize items, such as locations or automobiles, may be impacted by prosopagnosia. Many people also struggle with navigation. This may involve having trouble processing angles or distances or having trouble recalling specific locations and landmarks.

Prosopagnosia has no known treatment, however training programs are being developed to help with facial recognition and researchers continue to investigate the condition’s underlying causes. Some patients with prosopagnosia may profit from compensating techniques that facilitate face-to-face recognition. Many people with face blindness develop compensatory skills to aid with personal identification, such as hearing a person’s voice or recognizing them by their clothing or gait. They depend on context to help them figure out who people are and can be confused when encountering people out of context.