The Capgras delusion is an extremely rare disorder that leads somebody to believe at least one person close to them has been replaced by an imposter. It is impossible to convince somebody with Capgras that this is not the case through reason and logic.
While to many of us this condition exists only in the abstract, a piece of trivia to be prodded and poked with thoughts and theories, it is a horrifying reality for anyone living under the delusion. It must be truly traumatic. Imagine believing that you know - not think, but know - that a loved one such as your daughter, father, husband, wife, brother, or sister has been inexplicably ripped from your life, and an identical-looking person is for some reason pretending to be them, and seemingly getting away with it.
Conversely, imagine that (for example) your parent or child has developed Capgras delusion, and you are the one they believe has been replaced. Your presence will make them angry and upset. Just being in the same room would cause your loved one severe distress.
Although the condition was first formally reported by the eponymous French psychiatrist Joseph Capgras in 1923, it remains poorly understood. The most commonly accepted theory at the time of writing posits two roots to the delusion. Firstly, the connection between recognising a person and the associated emotions for that person has been severed; that is, Capgras allows one to recognise a person's looks, but not to access personal feelings about them. Secondly, the ability to recognise that this deficit results in a delusion is disabled. Add to that the fact that Capgras almost always accompanies at least one other neurological disorder (commonly dementia or paranoid schizophrenia), and its effects are powerful indeed.
Little-known and poorly understood conditions such as these are always interesting for those on the outside looking in, but we must never lose sight of the fact that the reason we know about them is that real, living and breathing human beings are affected by them. Rather than take a detached interest - considering the condition while discarding the humanity of those forced to live with it - I think we should strive to develop empathy. The interactive nature of games means that they occupy a perfect space in which we could not only educate ourselves on such matters, but gain a sliver of understanding (and hopefully more than a sliver of empathy) regarding what life must be like for those for whom this is a constant, traumatic reality.
Video games are primarily used for entertainment. Wonderful, unique entertainment. But by making a game about something like the Capgras delusion, their potential could be tapped still further. Brushing aside the natural feeling of otherness when it comes to things we don't understand, and replacing it with empathy, is surely worth a try.