People with face blindness can typically understand facially expressed emotions — they know whether a face is happy or sad, angry or puzzled. They can detect subtle facial cues, determine gender and even agree with everyone else about which faces are attractive and which are not. In other words, they see the face clearly, they just do not know whose face they are looking at, and cannot remember it once they stop looking.

What may seem like an obscure diagnosis is actually very common in the general population, according to related studies on a test sample of German students. Of the nearly seven hundred students tested, 2.47% displayed difficulties with recognition consistent with face-blindness. Independent tests at Harvard came to very similar conclusions. No specific gene has been located, though German researchers found that those with related conditions among family members were much more likely to display the same symptoms. Readers who are curious about their own facial recognition skills may take this related test sponsored by University College of London.