Australasian Science: Australia's authority on science since 1938

The Man Who Mistook His Cat for a Spy

By Tim Hannan

A new report describes a variant of Capgras syndrome in which a patient believed that his cat had been stolen by the FBI and replaced by an imposter that was spying on him.

Capgras syndrome is an uncommon but distressing condition in which the sufferer expresses the bizarre belief that a person known to them has been replaced by a near-perfect duplicate. Named after the French psychiatrist who provided the first description in 1923, Capgras is one of a range of delusional syndromes in which a person believes that a person, place or object has disappeared and been replaced by a duplicate, such as an alien, robot or meticulously constructed building.

Capgras sufferers declare that, while the person standing before them may seem identical in appearance and behaviour to their relative or friend, he or she is nevertheless an imposter. Most cases of Capgras occur following a brain injury or neurological illness, such as a traumatic brain injury, stroke, or the onset of dementia, and usually resolve when treated with medication.

A recent report in the journal Neurocase has documented a case in which a patient believes that his cat has been stolen by the FBI and replaced by an imposter. The 73-year-old man presented with a 6-year history of paranoid delusions, including the belief that he was being observed by government agents. He then advised his wife that his cat had been stolen and replaced by a near-perfect replica: while he agreed that the “new” cat appeared physically identical to his former pet, it did not feel like his cat, with its personality markedly different from his pet. He concluded that the cat was an imposter replaced by agents as part of the conspiracy against him.

The Neurocase paper is not the first report of delusions concerning animals, although such cases remain quite rare. The authors note only five prior reports of patients complaining that their furry or feathered friends had been inexplicably replaced by imposters: two cats, one dog and two birds. In all cases the delusion occurred in socially isolated individuals without regular contact with close friends or family, which suggests that the animal may have been the sufferers’ main relationship, and so the necessary object of the delusion.

The current neuropsychological explanation of Capgras syndrome proposes that two different brain impairments must be present at the same time.

First, Capgras sufferers have an abnormal perceptual experience of familiar people, which provides the basis for the content of the false belief. While the patient has normal visual, auditory and tactile experience of the known person or animal, the autonomic or physiological reactions that usually accompany that experience appear to be absent, resulting in a lack of emotion associated with the perception of the object. Lacking this “emotional confirmation”, the Capgras patient rationalises that the identity of the person or pet simply cannot match the one suggested by the perceptual input.

This conclusion is presumed to require a second deficit in a hypothesised “belief evaluation system”, which prevents the delusional belief from being rejected on the grounds of its implausibility. Thus for the patient the Capgras delusion is the best explanation of their perceptual experience.

In the present case, the patient is presumed to perceive his cat clearly and accurately, but he does not experience his former or usual emotional reaction to it. He concludes that therefore the cat cannot be his loved pet and, being unable to note the striking implausibility of this outcome, decides that it must be an imposter.

The report extends the current literature on Capgras syndrome by demonstrating that delusional syndromes involving misidentification can extend beyond persons and places to include animals. One implication is that cat-loving individuals who suffer certain brain injuries will be at risk of distrusting their former pet.

On the other hand, non-brain-injured people who do not like cats may be assured that if a partner’s pet is regarding you with a sullen and contemptuous glare, it is not spying for a federal agency: it really is out to get you.


A/Prof Tim Hannan is Head of the School of Psychology at Charles Sturt University, and the Past President of the Australian Psychological Society.