Misidentification syndromes are some of the most fascinating psychiatric disorders around. I would say ‘cool’ but I’m sure that suffering from one can be very dispiriting, and will continue to use this adjective for trainers and indie bands only. They involve a disturbance in the judgement of uniqueness of certain events.
First up, there’s Capgras Syndrome; also known as I’illusion de sosies (Illusion of doubles). Here, a person is under the impression that someone close to them has been removed and replaced by an identical looking impostor. It is named after Joseph Capgras, a French psychiatrist, who described this in a paper published in 1923.
Capgras Syndrome is associated with schizophrenia in more than half the cases. The theory behind it runs like this: when the eye sees a face, the brain processes the information in two parallel streams, which can be damaged independently. Faces are at once explicitly identified via the temporal cortex and also more rapidly though the amygdala, which is involved with the limbic – emotional processing – system. We can see an example of this rapid processing if we were to find ourselves running away from something without fully understanding what it is.
If the temporal cortex path is damaged, the brain will have difficulty in recognising a face. However, via extra-visual clues, emotional responses to familiar faces are preserved. Therefore someone with prosopagnosia (inability to recognise faces) will still have an emotional response to the faces of people they know. If the amygdala path is compromised then the person will still recognise the face, but the expected emotional response will be absent. This could lead the feeling that a familiar face is ‘not quite right’ and to the erroneous conclusion that his is because of an impostor.
Subtly different is Fregoli Syndrome. Rather than named after a pioneering psychiatrist, this disorder was named after Leopold Fregoli (1867-1936) who was an Italian actor and the greatest quick change artist of this day. He was famous for his ability in impersonations and his quickness in exchanging roles, so much so that at times rumours spread that his act was in fact performed by more than one person. This is also known as the illusion of a negative double, and the suffer believes that various people he or she meets is actually the same person in disguise. This often has a paranoid flavour, with the sufferer believing that that are pursued by a someone that assumes different identities.
A sort of combination of Capgras Syndrome and Fregoli syndrome is intermetamorphosis syndrome, first described by P Courbon and J. Tusques (1932); in this, the subject develops the delusional conviction that various people have been transformed physically and psychologically into other people. This disorder involves false physical resemblance and false recognition.
Almost there. Reduplicative paramnesia was described by Pick in 1903 and is often seen in post traumatic brain injuries. With this, there is a belief that a familiar person, place, object or body part has been duplicated. For example, a person may believe that they are in fact not in the hospital to which they were admitted, but an identical-looking hospital in a different part of the country.
Finally, there’s delusion of subjective doubles, in which a person believes there is a doppleganger or double accompanying the self. Apparently meetings with doubles were a popular theme of 19th century romantic literature (see Dostoyevsky’s The Double). It was believed that we each have a doppleganger who normally remains unseen; if we see our doppelganger then death is imminent…