Face Blindness, Prosopagnosia, is a disorder that impairs your ability to recognize faces. While other cognitive functions remain the same you have trouble recognizing the faces of your friends, family, and even your own. In some cases your brain will tell you recognize strangers you never met before. The difference between a friend and a stranger can be broken down to a specific part of the brain, and at times broken. Think of that the next time you look in the mirror, or meet up with a friend.