'Cat-gras' Delusion: The Man Who Thought His Cat Was an Impostor

Author: Agata Blaszczak Boxe


An older man in Massachusetts had a truly nightmarish experience: a sneaky feline impostor found a way to take over the body of his beloved cat and inject its own personality into it. What's worse, the cunning impostor cat was conspiring against the man. And so was the FBI.

At least that's how the man saw it—this bizarre scenario, the alleged cat impostor and the FBI conspiracy were part of a delusion and a symptom of the man's disorder his doctors dubbed "Cat-gras"—a feline version of Capgras syndrome. People with Capgras syndrome become convinced that someone (in most cases, an actual human) they know had been replaced by an identical-looking impostor.

The mechanisms behind Capgras syndrome and related conditions collectively called delusional misidentification syndromes are a bit of a mystery. The syndrome is named after Joseph Capgras, a French psychiatrist who first described the condition in 1923 in a woman, "Madame M.," who thought impostors had taken the places of her husband and friends. Most commonly, Capgras delusion occurs in people who have schizophrenia, certain brain injuries or dementia.

Capgras delusions involving an animal impostor, as opposed to a human one, seem to be quite rare. There have been two other reported cases of delusions involving cats, two involving pet birds and one in a pet dog.

For the man described in the new report, problems started long before he began to think his cat had been replaced. A couple of years ago, at the age of 71, he went to a neurobehavioral clinic in Boston because of memory problems and overall decline in functioning. There, the doctors found he had a history of heavy alcohol use and repeated head traumas from playing professional hockey in the past, as well as sleep and heart problems. "He was a very complex individual," said Dr. R. Ryan Darby, at the time affiliated with Massachusetts General Hospital in Boston, who treated the man and coauthored a report of his case, published recently in Neurocase.

About 15 years before coming to the clinic, the man had been forced to retire from his job due to his aggressive outbursts against coworkers. He eventually was admitted to a psychiatric hospital, where his doctors diagnosed him with bipolar disorder. During the next 15 years, the man had episodes of manic behavior that included spending $40,000 in one month on golf-related paraphernalia and a car. The man also had a hoarding problem, which caused him to fill his spare bedroom with old magazines and electronics.

Six years before the man saw the doctors who described the case, he became extremely paranoid after he had stopped taking his psychiatric medications. He passed his wife written notes claiming that their house was being monitored and thought that random people in parking lots were really FBI agents. Finally, he started experiencing the cat impostor delusion.

At the time of the man's initial examination at the clinic, neuropsychological testing showed that he had confabulation and impairment in executive functions and memory retrieval. A CT scan revealed the man had experienced a loss of brain cells, softening of the brain tissue, and injuries in the frontal parts of the brain from past trauma.

The man's symptoms improved with medications and his delusions eventually subsided. Darby said the last time he spoke to the man's wife about six months ago, his condition had been stable and his delusions had not returned.

Most of the few other reported cases of Capgras involving pets occurred in people experiencing a psychotic episode and accompanied other paranoid delusions, like in the case of this patient. However, the new case is unique in some ways, the authors said. For one, the previously reported cases involving animal delusions occurred in people who were socially isolated from family and friends—something that was not the case for this patient. Moreover, the other cases have been reported only in psychiatric patients—but the current patient also had previous brain injury. Though it is not clear whether this injury actually contributed to the man's symptoms in any way, it is a possibility, the researchers said. "I think there is a decent chance that it did but I think it is hard to say that because of those other things that had been going on," such as the man's history of bipolar disorder, Darby said.

Although it's unclear what drives this peculiar delusion, some theories have been proposed over the years. Some researchers have suggested, for example, that damage to certain pathways involved in recognizing familiar faces could be involved. Others have suspected that a disconnection between areas involved in understanding mental states of others, as well as problems with emotional and memory processes might explain the bizarre symptoms.

Given this man's problem with retrieving memories, his doctors propose another theory; that the delusions may result from a problem with linking an object (such as a cat) a person can see with his memories of this object. In other words, if you can't properly retrieve your memories about a familiar object, you may think the object is new, but very similar to something you know, like a replica, or an impostor.