Prosopagnosia (from Greek prósōpon, meaning "face", and agnōsía, meaning "non-knowledge"), also known as face blindness, is a cognitive disorder of face perception in which the ability to recognize familiar faces, including one's own face (self-recognition), is impaired, while other aspects of visual processing (e.g., object discrimination) and intellectual functioning (e.g., decision-making) remain intact. The term originally referred to a condition following acute brain damage (acquired prosopagnosia), but a congenital or developmental form of the disorder also exists, with a prevalence of 2.5%. The brain area usually associated with prosopagnosia is the fusiform gyrus, which activates specifically in response to faces. The functionality of the fusiform gyrus allows most people to recognize faces in more detail than they do similarly complex inanimate objects. For those with prosopagnosia, the method for recognizing faces depends on the less sensitive object-recognition system. The right hemisphere fusiform gyrus is more often involved in familiar face recognition than the left. It remains unclear whether the fusiform gyrus is specific for the recognition of human faces or if it is also involved in highly trained visual stimuli.
Acquired prosopagnosia results from occipito-temporal lobe damage and is most often found in adults. It is subdivided into apperceptive and associative prosopagnosia. In congenital prosopagnosia, the individual never adequately develops the ability to recognize faces.
Though there have been several attempts at remediation, no therapies have demonstrated lasting improvements across a group of prosopagnosics. Prosopagnosics often learn to use "piecemeal" or "feature-by-feature" recognition strategies. This may involve secondary clues such as clothing, gait, hair color, skin color, body shape, and voice. Because the face seems to function as an important identifying feature in memory, it can also be difficult for people with this condition to keep track of information about people, and socialize normally with others.