Brain and Body

This Strange Neurological Disorder Made a Man Believe His Cat Was an Evil Imposter

January 27, 2016 | Kelly Tatera

An angry cat with glaring red eyes


The brain works in mysterious ways, and one of the stranger neurological conditions out there is called Capgras syndrome – when the mind tricks someone into thinking that a person has been replaced by an imposter doppelgänger.

These paranoid beliefs usually involve a family member, friend, or loved one, but in a particularly strange case, a man thought an imposter had taken the form of his pet cat.

In what neurologists have coined “Cat-gras Delusions,” researchers from Harvard recently published a paper detailing this peculiar case in the journal Neurocase.

After fishing through the 71-year-old man’s medical records, the researchers found he had bipolar disorder as well as a history of heavy drinking and sports-related head injuries. After the man stopped taking his psychiatric medications, he initially suffered from delusions that the FBI was monitoring him.

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Six years later, the delusions evolved to the belief that his cat had joined this conspiracy against him. Strangely, “he knew that the current cat resembled his pet cat physically, but that the personality or psychic core of his cat had been replaced,” the study explains.

What causes these delusional beliefs? The neurologists attribute the phenomenon to a brain glitch during retrieving autobiographical memory, which is the collection of our past experiences. In healthy brains, information is retrieved from an internal log of autobiographical memories when a new external stimulus is perceived. This process allows new stimuli to be associated with past experiences.

However, in the brain of someone with Capgras delusions, the perception of external objects – people, or in this case, a cat – doesn’t trigger the appropriate retrieval of autobiographical memory. This is why the man could associate his cat with “practical” attributes, like recognizing that his cat was a cat, but the disassociation with his emotional memory is what caused him to believe his cat had been taken over by an evil imposter.

The neurologists looked at the man’s brain scans, and evidence hinted that this delusional thought pattern was linked to the deterioration of his cerebral cortex, the area of the brain associated with higher cognitive skills. The scientists say this process is similar to dementia, and that there was no doubt that the numerous head traumas he had received while playing ice hockey contributed to the problem.

Most people who suffer from Capgras syndrome — an estimated 81 percent, in fact — also suffer from other neurological diseases and mental health issues. In particular, it’s been linked to Lewy body disease, which is a type of dementia.

This was the first ever case of Capgras syndrome that involved a cat. There have, however, been two previously reported cases of delusions towards dogs and and two other ones towards pet birds — all prime examples of the brain’s perpetual enigma.

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