Prosopagnosia - “You seem familiar, but I can’t place your face”

Prosopagnosia is a neurological disorder characterized by the inability to recognize familiar people based on facial information alone. Prosopagnosia, often called facial blindness, can be acquired through lesion, stroke, head trauma, or manifested without any discernible cause. Other patients with prosopagnosia may have developmental prosopagnosia (DP), which is characterized by a lifelong deficit in facial recognition and cannot be traced to acquired brain damage. A patient with DP may not be aware of this deficit because they would form the ability to recognize people by other distinguishing features that are unrelated to their facial characteristics. For patients with DP, the ability to recognize objects can be completely unaffected or only slightly impaired, but they may struggle to recognize close family members, friends, or themselves. At one time, DP was believed to be an extremely rare disorder, with only $9$‍ case studies conducted between $1947$‍ and $2001$‍. In recent years this belief has been challenged as increased numbers of patients are diagnosed with DP, and researchers now believe that as many as $1$‍ in $50$‍ people may have some form of prosopagnosia.

A researcher interested in prosopagnosia conducts an Internet survey in which respondents click a link, sign into a Social Media site, and are connected to a test battery that shows them a series of photos of famous faces. Each face is isolated from any other identifying features and is presented with eyes forward, as shown in Figure $1$‍, which shows the isolated face of Barack Obama, adapted from President Obama’s $2008$‍ Official Presidential Portrait.

As each photo appears, the subject is asked to provide the name they associate with the presented face. If the subject is not able to remember a name, they are told to provide a description of the famous person's work or experiences. Once the subject submits this response, the famous person's name is revealed and the subject is asked to self-report whether their response was correct or incorrect. If the name presented is unfamiliar, the subject selects a radio button labeled, “I do not know this person” and their response is not counted against their accuracy score. Afterwards, the researcher calculates the percentage of correct answers, excluding the pictures described as unfamiliar. The percentage of faces recognized by each respondent is presented in Figure $2$‍, and mean accuracy across all respondents is $82\mathrm{\%}$‍.

Figure $1$‍

Figure $2$‍