Brain Syndrome Can Make Owners Think Pets Are Impostors

What Capgras Syndrome reveals about the depths of our relationships with pets.

Posted Apr 25, 2018

Photo by aleksandrrr/123RF
Source: Photo by aleksandrrr/123RF

Mary was 40 years old when she became convinced that Sarah, her 9 year old daughter, was an impostor.  The real Sarah, she told relatives, had been taken away and placed into a foster home. She claimed social workers had replaced her actual child with an identical-looking impostor.  Mary was so convinced of this substitution that she would sometimes refuse to pick her daughter up at school. Mary would scream to the teachers, “Give me my real daughter back, I know what you have done!” 

To no avail, her family and health care providers tried to convince Mary that no substitution had occurred, that Sarah was indeed her real daughter.  But even after Mary was treated with risperiodone, a powerful anti-psychotic drug, she held on to the delusion. The local Department of Social Services became concerned about her ability to raise a child. And when it became apparent that Mary could no longer provide care for the daughter who she believed was an impostor, they successfully sought legal guardianship for Sarah. At one point during the hearing, Sarah told the court, “I love my mother, except when she doesn’t believe I’m me.”

As described in an article by Drs. Jeremy Matuszak and Matthew Parra in the journal Psychiatric Times, Mary was suffering from Capgras Syndrome. This is a rare variant of a group of neuropsychiatric conditions called delusional misidentification disorders.  First identified in 1923 by the French psychiatrists Joseph Capgras and Reboul-Lachaux, individuals with the Capgras delusion come to believe that a person they know has been replaced by an identical-looking impostor. Usually the target of the delusion is a family member or a loved one. In Mary’s case, it was her young daughter. 

I first ran across Capgras syndrome while reading the neurologist V. S. Ramachandran’s book, Phantom’s in the Brain. In it, he describes the case of a man who suffered a brain injury in a car accident and suddenly became convinced his father was an impostor.  But in his book, Ramachandran briefly mentions his patient Steve who believed that his pet poodle Fifi had been replaced by an impostor dog. The real Fifi, he told Ramachadran, now lives in Brooklyn. Intrigued by this story, I recently combed the published neurological literature for instances of Capgras syndrome in which people were convinced that their pets had been substituted with an impostor. The cases are remarkable, and they shed light on the importance of animals in our psychological lives.

Sophia’s Dogs

Take, for example, an Italian woman I will call Sophia whose case was described in the journal BMC Psychiatry. In 2011, Sophia developed tremors and stiffness in the right side of her body. A series of neurological tests revealed she was in the beginning stages of Parkinson’s disease. A regime of anti-Parkinson medications seemed to relieve her symptoms.  But in November, 2013, she began to claim that her dogs had been replaced by impostors who looked exactly like her real pets.  When she was asked why anyone would replace her pets, she admitted that she did not have a clue. Further, she could not name any physical features on the “impostor” animals that were different from her “real” pets.  Sofia was diagnosed as having a delusional disorder, and she began treatment with anti-psychotic drugs. Unlike Mary who continued to believe her daughter was an impostor, Sofia got better.  By November 2014, she acknowledged that her belief that her dogs were impostors had been irrational. However, while she improved dramatically, she admitted that she sometimes had the feeling that things were not quite right with her pets.

Published Cases of Pet-Related Delusional Syndrome

I was able to track down eight additional cases of Capgras delusions aimed at pets, and they reveal the depths of our relationship with companion animals.

  • Drs. Ryan Darby and David Caplan reported the case of a 73 year-old former professional hockey player who had lots of problems -- alcohol abuse, sleep apnea, heart disease, a history of head trauma, and bipolar disorder.  The authors wrote, “He became obsessed with the idea that his pet cat had been replaced by an impostor cat that was involved in a conspiracy against him. He knew his current cat resembled his pet cat physically, but that the personality of the psychic core of his cat had been replaced.”  The good news is that the man’s delusion completely disappeared after treatment with medication.   
  • Dr. David Somerfield published a report of a 91 year old woman with a history of psychosis whose Capgras delusion focused on her parrot.  When she would stop taking her meds, she would accuse people of “swapping” her pet for a look-alike.  As in the previous case, her symptoms went away when she took her meds.
  • A 2001 report in the Journal of Neuropsychiatry and Clinical Neurosciences also involved a pet bird. The patient was a 67 year-old woman admitted to a psychiatric facility due to an age-related form of schizophrenia.  Socially isolated, her best friend was a canary. Because she was so concerned about her pet, the staff said could keep her bird near her bed in the hospital.  But, as the researchers wrote, “During the first two days, she repeatedly asserted that the canary in the cage was not her canary. She reported that the bird looked exactly like her canary, but was, in fact, a duplicate.” Her symptoms were alleviated with anti-psychotic medications. 
  • A 1999 article titled “A Zoocentric Capgras Syndrome” described the case of a 23 year old woman, “who had the delusion that her cat had been replaced by the cat of her former boyfriend.” Unfortunately, the article is written in German so I don’t have details about the case. 
  • A 1981 report in the Canadian Journal of Psychiatry described the case of a 19 year old male college student diagnosed with schizophrenia. He claimed he could read people’s minds and that God had chosen him to perform miracles. And he also believed his dog had been replaced by a double.  Indeed, during a phone call he asked his mother to have his pet bark into the telephone. But even then he refused to believe the dog was his pet. 
  • Researchers at Leeds University reported two cases of canine Capgras. Both involved women and their dogs. The first involved a 76 year-old spinster who was hospitalized after she barricaded herself in her apartment and insisted that her dog was an impostor. She also claimed her neighbors had entered her house and replaced her furniture with identical substitutes. She said her real dog would never have allowed this to happen. Her brain scan was normal, and she had no history of mental illness. She improved after being treated with antipsychotic medication.  Unfortunately, her dog died a month after she was discharged from the hospital.  She eventually got a new dog which she never claimed was an impostor.
  • In their second case, a 57 year-old woman living alone was diagnosed with schizophrenia when she developed a host of paranoid delusions. She claimed there was a conspiracy to drive her insane and that people wanted to knock her off her bicycle.  She also believed her close relatives and her dog were impostors. She said the impostor dog was exactly like her real dog, only larger. (She also felt her impostor relatives were different sizes than her real relatives.) With medication, she improved. Yet she never completely gave up her Capgras delusions, and she died unexpectedly of a heart attack at the age of 59.

What Causes Animal Capgras Delusions?

I admit that nine cases is a small sample, but some interesting patterns did emerge among this group of patients. For example, twice as many women as men thought they were living with

Graph by Hal Herzog
Source: Graph by Hal Herzog

impostor animals.  And, as group, the patients tended to be on the old side. Six of eight individuals were over 50, and half were in their late 60’s or older. While only two of the patients had suffered identifiable brain damage, nearly all the patients had been diagnosed with a functional psychosis, usually a form of schizophrenia.  Finally, all seven of the patients which there was information on treatments were given anti-psychotic drugs. In nearly all of these cases, their pet impostor delusions diminished, and in several cases, they seemed to have disappeared.

Speculations about the causes of Capras syndrome abound. The some researchers argue that impostor delusions are a way of subconsciously dealing with love-hate conflicts. V. S. Ramachandran believes that imposter delusions result from disconnections between emotional and face recognition centers in the brain.  Others argue it is usually the result of degenerative diseases such as Alzheimer’s and Lewy body disease. Indeed, impostor delusions have been associated with a wide array of conditions including psychiatric disorders, strokes, tumors, epilepsy, and even vitamin deficiencies and drug use.  

Does Animal Capgras Syndrome Reveal That Pets Really Are Family Members?

An important characteristic of Capgras delusions is that the objects of the substitutions are typically family members - wives, children, parents, siblings.  Indeed, Dr. Elfed Price has offered an interesting evolutionary perspective on Capgras syndrome. He argues that Capgras is fundamentally a kin recognition disorder, a malfunction of neural mechanisms that enabled our ancestors to readily identify individuals they shared genes with.   

But doesn’t the fact that these delusions can focus on pets rather than people refute Price’s idea.  Not at all. Price makes the case that in recent years pets have become kin, but in a social sense rather than a biological sense. He is right. According to a 2018 Harris Poll, 69% of Americans regard their pets as family members, and 23% of owners say their pets are their children. Does the existence of people who believe their dogs and cats are impostors provide neurological evidence that we really do consider companion animals as members of our family?  

I think Dr. Price is on to something. What Capgras shows is that we really do think of pets as people.


Darby, R. R., & Caplan, D. (2016). “Cat-gras” delusion: a unique misidentification syndrome and a novel explanation. Neurocase, 22(2), 251-256.

Ehrt, U. (1999). A zoocentric Capgras syndrome.Psychiatrische Praxis, 26(1), 43-44.

Matuszak, J., & Parra, M. (2011). That’s not my child: a case of Capgras syndrome. Psychiatric Times, 28(2), 46-46.

Ramachandran, V. S., Blakeslee, S., & Shah, N. (1998).Phantoms in the brain: Probing the mysteries of the human mind (pp. 224-25). New York: William Morrow.

Raschka, L. B. (1981). The Capgras syndrome. The Canadian Journal of Psychiatry, 26(3), 207-208.

Somerfield, D. (1999). Capgras syndrome and animals.International Journal of Geriatric Psychiatry, 14(10), 893-894.

Wright, B., Mindham, R., & Burn, W. (1994). Canine Capgras. Irish Journal of Psychological Medicine, 11(1), 31-33.

Rösler, A., Holder, G., & Seifritz, E. (2001). Canary Capgras.The Journal of Neuropsychiatry and Clinical Neurosciences,13(3), 429-429.