I found the topic of prosopagnosia very interesting so I decided to research it further. Prosopagnosia is the inability to recognize faces and results after a stroke or brain injury. Recently is has been discovered that it may also be a developmental or congenital disorder and can run in families. The patient has never suffered from a brain injury but they never properly learn the ability to distinguish different faces. Tests used to diagnose prosopagnosia involve the patient being asked to identify famous faces. But because some famous people may be unknown to a particular generation, this test is not as reliable. There are two tests that require participants to identify novel faces rather than famous faces which are, the Cambridge Face Memory Test and Cambridge Face Perception test. These tests are the most theoretically strong tests for prosopagnosia since they require the identification of novel faces rather than famous faces. The Cambridge Face Memory Test requires recognition of six learned faces but in three different stages. These stages are recognition of the same images, recognition of the same faces in different images and recognition of the same faces in different images covered with a heavy visual noise. The Cambridge Face Perception differs in that it requires participants on each trial, to order a series of faces for similarity to a target face. The comparison stimuli for these trials consist of a face that was morphed into several different faces by certain degrees.
In a case study of participant B, a 7 year old male is diagnosed with a severe deficit in face recognition. The participant never suffered from any brain injuries therefore he suffers from developmental prosopagnosia. To determine if the child had a deficit, the researchers evaluated his face recognition skills by requiring him to recognize faces, discriminate between faces, identify emotion, and recognizing objects. The results showed that the participant answered correctly on 46.8% of trials whereas a normal child averages 80% on this test. This shows that the participant has a sever deficit in the ability to discriminate faces, recognize objects, and identify emotion. (http://www.journalofvision.org/content/11/11/571.abstract)
Prosopagnosia is a devastating, life altering disorder that makes the patient feel disconnected to others. This video is interesting and shows just that : http://www.youtube.com/watch?v=vwCrxomPbtY