When you look in the mirror, you see yourself and know it’s you. This ability to recognize one’s own reflection is only shared by a very small number of animals, including elephants and dolphins. But in very rare instances, this kind of self-awareness can go wrong, just like in the curious case of a French man who thought his own reflection was another man standing behind his mirror.
You may have heard of face blindness before, or prosopagnosia, which as the name suggests is an inability to recognize faces, but in some cases this can extend to other things like animals or objects. This isn’t quite the same, though, because this man was able to recognize that there was a face staring back at him, he just thought it belonged to someone else.
Described in the journal Neurocase, the patient was a 78-year-old individual, “Mr. B.,” who was admitted to hospital in Tours, France, for both behavioral and psychological problems. It all began 10 days earlier when he started seeing a strange man behind his bathroom mirror. A double of Mr. B, he was the same build, wore the same clothes and had the same features. The patient had no idea the man he was seeing was his own reflection.
Mr. B then began engaging with the man, finding he even acted the same way, and was surprised to find that the stranger knew so much stuff about him. He was so convinced that his new bathroom guest was a real person that he even brought the stranger food and cutlery. Eventually, Mr. B reported that the man had started behaving aggressively, and it was at this stage that his daughter took him to hospital.
Here, the man was given a health MOT to try and work out what was going on, but most tests were pretty unremarkable: blood tests were normal, as were his vital signs and EEG. An MRI scan revealed some wastage towards the back of the brain, though, and he had markers indicative of Alzheimer’s. He was prescribed an anti-anxiety medication because he was stressed about living with a stranger, lead author Capucine Diard-Detoeuf told LiveScience, and an anti-psychotic for his psychosis. Remarkably, three months on and he was no longer experiencing these delusions.
So what was going on? The authors describe two similar cases, documented more than 20 years apart, both involving women who had experienced degeneration in parts of the brain, and both saw body doubles in the mirror that they misidentified as another person. These were diagnosed as having an unusual form of Capgras syndrome, the delusional belief that a close relative or friend has been replaced by an identical imposter.
Facial recognition involves two distinct neural pathways: “overt” or conscious recognition, and “covert” recognition, which is without awareness. People with prosopagnosia have a loss of overt recognition, yet still react to familiar faces due to the preservation of covert recognition, which bestows a sense of familiarity. But in the case of Mr. B and the other similar reports, it’s likely that both pathways were affected, and thus represent atypical Capgras syndrome, the authors conclude.
[H/T Live Science]