The man who saw a stranger in the mirror

Mirrors easily call forth the uncanny: the vampire that casts no reflection; the figure who seems to appear in your periphery. Overtired or in an odd mood, I sometimes find myself scrutinising my own reflection, momentarily toying with the idea that it's something independent, alive in its mirror space. So I was fascinated to read a short account published in the journal Neurocase of a 78-year-old man, referred to as Mr B to protect his privacy, who over the course of ten days, in place of his own reflection had repeatedly encountered a doppelganger in the mirror: a stranger who looked just like him, and knew all about him, but a stranger nonetheless. Eventually, this figure "became aggressive" – the article doesn't share any details – and it was presumably this change in tone that triggered Mr B's admission to hospital.

Mr B, who had no history of psychiatric illness, was diagnosed with a form of Capgras syndrome. People with Capgras believe that one or more familiar people have been replaced by identical strangers, and it falls within the delusional misidentification syndrome, together with related conditions such as the Fregoli delusion: the belief that many people you encounter are actually a single deceiver in disguise. It's likely that such delusions involve some degree of impairment in face processing, specifically the ability to process familiarity of other people's faces: in Cagras the familiar feel somehow not (an experience undergirded by skin conductance response data); in Fregoli the many feel somehow the same. If this hypothesis bears out, these delusions could be seen as the complement – or mirror image – of prosopagnosia (also known as face-blindness), where explicit recognition of faces is impaired, but sufferers still retain their implicit feelings about faces, correctly guessing which belong to people they know.

What's interesting about Mr B's mirrored-Capgras, also called mirrored self-misidentification, is that the delusional judgment is applied to one's own face. Evidence suggests that our brains process own-face information in a special way, suggesting that this particular experience reflects a specific brain impairment, rather than the delusion arbitrarily settling on one target rather than another. The authors of the Neurocase article don't report too deeply on Mr B's neurological symptoms, mentioning only some protein indicators consistent with Alzheimer's Disease, and atrophy in chiefly posterior brain regions. We would expect some damage also within the dorsolateral prefrontal cortex, as this is typical in patients experiencing such delusions. This area is involved in evaluating beliefs, and stepping in to question extreme or incoherent ideas.

Mr B was given antidepressant and antipsychotic medication in hospital, and three months later, he had recovered from his delusion: "Mr. B. explained that his double had gone." It's nearly Halloween, where we get to play tricks with the uncanny. Maybe spare a thought for the tricks that that the uncanny can play on us.

Further reading

Diard-Detoeuf, C., Desmidt, T., Mondon, K., & Graux, J. (2015). A case of Capgras syndrome with one's own reflected image in a mirror Neurocase, 1-2 DOI: 10.1080/13554794.2015.1080847