simple explanations of interesting brain conditions

My Family Are Impostors: the Capgras Delusion

Picture this; you’re sitting at home minding your own business when your dog comes running through the door and bounds over onto your lap… except it’s not your dog. Sure, it looks like your dog, identical in every way- but some deep instinct tells you this is an imposter. Your parents walk past and give you a smile, but your stomach lurches because in your heart you know those people aren’t your family. Sounds a bit like a horror movie but some people really experience this feeling, now known as the Capgras delusion. I’ve even experienced it once myself, but we’ll get to that later.

French psychiatrist Joseph Capgras (1873-1950) first described the disorder in 1923. In his paper Capgras wrote of a woman known as “Madame M.” who had become convinced that “doubles” had replaced the people around her, including her husband. Capgras described the syndrome as “l’illusion des sosies” or “the illusion of look-alikes”. Today we understand the Capgras delusion as a type of mental or neurological illness involving delusions about the true identity of a person, object or place. The delusion most commonly occurs in people suffering from paranoid schizophrenia, but has also been observed in those with brain injuries, dementia and diabetes. People suffering from the Capgras delusion usually begin to doubt the identity of familiar people such as their partner or family members, but occasionally these doubts extend to other things such as their pets, cars or even houses. In some extreme cases patients will even begin to doubt their own identity, convinced that they are an imposter in their own life.


So yeah, freaky stuff, and we’re not even completely sure what causes it.  In 1990 psychologists Hayden Ellis and Andy Young hypothesized that patients might have damage in the systems that regulate emotional reactions to familiar objects. Vilayanur S. Ramachadran (who you might remember from my split-brain article) has investigated this theory and suspects that there might be a disconnect between the area of the brain where faces/objects are visually recognized (the temporal lobes) and the area involved in producing emotions (the limbic system). Below Ramachandran explains in detail through the amazing story of Capgras sufferer David:

Nova: Season 28 Episode 13 – Secrets of the Mind (2001)

Dissociactives, Capgras and My Experience

In one 2010 study on the effects of ketamine, researchers happened to induce Capgras delusion in a healthy 26-year-old graduate student. The student participated in the study over a four-day period during which she was administered both ketamine and placebos; during this period she began to develop delusions about the identity of both the researchers and herself:

“Every time you left [the researcher] the room, I thought another person dressed in your clothes was coming back into the room . . . it wasn’t scary, just another person dressed in your clothes, doing your job, but the person was a little older in age and weighed more.” She also reported: “I’d look into the mirror and think that’s not me, I didn’t think the image staring back at me was myself . . . even the words I was saying were not words I would normally say . . . it just wasn’t me . . . it wasn’t my speech, my voice, my reactions . . . I felt like a different person because I would not have reacted in the way I usually would have.”

As mentioned earlier, I myself have experienced extreme Capgras delusions while under the influence of mind-altering chemicals. It happened while experimenting with the plant Salvia divinorum, which was legal to buy and use at the time. Interestingly enough both ketamine and Salvia are dissociatives; meaning that they reduce signals between the conscious mind and other parts of the brain. My experience was extremely intense; almost instantly I became convinced that the entire universe around me was an evil imposter, out to trick me for some nefarious reason. Luckily the effects of Salvia are short lived, and wore off in 20 minutes or so. I can’t even begin to imagine the sheer terror those who suffer true Capgras must experience.

In some cases, such as David’s and my own, the delusions simply fade with time. Some patients required therapy, others require anti-psychotics. It’s a horrifying condition that is hard to understand unless you’ve experienced it. How could an otherwise rational person become convinced of something so outrageous? I guess that’s just the strange reality of these delicate systems we call our brains. Some poor souls out there with damaged systems are doomed to live out their lives, convinced that those closest to them have been replaced.


All images produced by the author unless otherwise specified.

  1. Philip R. Corlett, Deepak C. D’Souza, John H. Krystal. (2010) Capgras Syndrome Induced by Ketamine in a Healthy Subject, Biological Psychiatry, Volume 68, Issue 1, Pages e1-e2, ISSN 0006-3223,  



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