What is prosopagnosia?
Prosopagnosia is an impairment in the ability to recognise the faces of familiar people. This impairment cannot be explained by poor eyesight and so it is believed to be related to the way in which the brain processes the visual information about a face. Prosopagnosia is diagnosed on the basis of low performance on tests of face recognition and learning. People are shown images of faces and they have to report whether they are familiar or not known. These tests include recognition of famous faces which are well known from popular culture, and faces which are learned during a testing session. Importantly, prosopagnosia is not a lack of knowing who people are, rather, it could be thought of, as a disconnection between knowledge of people and their visual appearance.
Everyone has difficulties recognising people from time to time; however, prosopagnosia is a more severe and persistent problem. Typically prosopagnosia will manifest itself in daily life as difficulty in finding a friend in a crowded place, or following characters in films (especially if there are changes in clothing or hairstyle). Individuals with prosopagnosia may experience some other visual or memory deficits. Faces contain important information other than the identity of the person, and some people with prosopagnosia have difficulties with recognising emotional expressions, or interpreting other social cues such as direction of eye-gaze. Additionally, some level of difficulty recognising specific examples of other visual objects, such as a particular car or tool is quite common.
Difference between acquired and developmental prosopagnosia
Historically, prosopagnosia was regarded as a relatively rare consequence of head injury or stroke. However, another type of prosopagnosia of a developmental origin has recently been found to be much more common than prosopagnosia acquired in adulthood. This type of prosopagnosia occurs without any apparent brain damage and is known as developmental or congenital prosopagnosia. Current estimates of the prevalence of developmental prosopagnosia range from 1.9% to 2.5%, and both family and twin studies suggest a strong genetic contribution for face-recognition ability in the general population. Because developmental prosopagnosia has only recently become the focus of systematic research, relatively little is known about its developmental origin and trajectory. Current research is concerned with discovering the nature of the perceptual and cognitive processes that are affected, and its neural basis.
Do I have prosopagnosia?
If you feel that you have persistent trouble recognising familiar faces in day-to-day life then you may be prosopagnosic. If you want to learn more about your face recognition ability the first step is to take an on-line test, the Cambridge Face Memory Test (CFMT). Our on-line version follows the format of the original CFMT (Duchaine and Nakayama, 2006) but uses faces from the Australian National University Face Database and the Glasgow Unfamiliar Face Database (McKone, Hall and Pidcock, Australian National University, 2009).
At the beginning of the test you will be asked for your first name, age, gender, country of residence and email address. If you perform poorly on this test, then a member of the Brain and Behaviour Lab may email you to invite you for follow-up testing at our lab. The tests at Birkbeck will be more detailed than the on-line test and will give you a better idea about the extent of your face recognition impairment.