Body doubles and alien replicants: Capgras delusions explained

July 16, 2014 by Ricky Van Der Zwan, The Conversation
The way we perceive things gets divvied up to different parts of our brain. Credit: Brittany Greene/Flickr, CC BY-NC-ND

In the film Invasion of the Body Snatchers aliens invade earth by replicating individuals. While the idea that we could be duped by shape-shifting aliens is a great idea for a film, the story echoes a bizarre appeal playing out around Senate elections in the United States.

Senate candidate Timothy Ray Murray has reported that he believes that his political opponent, Senator Frank Lucas, is dead and being impersonated by a body double.

Actually, in what initially seems more like a pitch for an episode of the TV series Get Smart than an alien invasion, Candidate Murray claimed that Senator Lucas died in 2007. He was then replaced by a body double.

Subsequently – Murray claims – that body double was hanged in the Ukraine in 2011 before being replaced by a body double double.

While it is tempting to think that Candidate Murray may be on to something – the idea that governments are populated by emotionless aliens carries considerable intuitive appeal – it is more likely that Candidate Murray may be suffering a Capgras delusion.

Capgras delusions

Described first in 1923 by French psychiatrist Joseph Capgras and his colleague Jean Reboul-Lachaux, Capgras delusions are characterised by the belief that someone known to us – a friend, spouse, child, parent or whomever – has been replaced by a physically identical impostor.

If that sounds familiar, or if a dearly loved elder has accused you of not being whom you claim to be, it is because these types of delusions are not uncommon.

Indeed, Capgras delusions are part of a larger group of misperceptions known as delusional misidentification syndrome.

More common in females than males by a ratio of three to two, Capgras delusions can occur in patients with paranoid schizophrenia or with neurodegenerative diseases, including dementia.

They can arise also as a result of , diabetes, or hypothyroidism. Capgras delusions have been reported even in association with migraine headaches.

Treatments can be successful, depending on the cause. Anti-psychotics can alleviate Capgras delusions, as can some drugs that treat comorbidities.

What is clear is that Capgras delusions arise as the result of some type of neural dysfunctioning.

Divide, conquer and perceive

Clues to how Capgras arise come from understanding how brains generate perceptions of the world.

When confronted with high-value but complicated cues, brains have evolved a simple solution: divide up information and process different types of information separately.

For example, our visual system processes information about what is out there (objects) separately from information about what is happening to those objects (actions); that is, colour and shape are processed separately from motion, direction and location.

If that seems hard to believe, it's because our everyday experience is not of those qualities being separate. A quick look around reveals an integrated experience with coloured objects moving around us.

Pathologies do arise, however, that confirm the "separateness" of the underlying mechanisms. Some individuals can see objects but not how they move in a condition called akinetopsia.

Conversely, individuals with agnosia report being able to tell where something is and what it is doing, but not what it is that they see.

Theories of mind

When it comes to people – perhaps the most high value targets we have ever to process – the same type of strategy applies.

Information about how someone looks and sounds, even how they move, is processed by brain mechanisms separate from those that help us form what is known as a theory of mind.

We form a theory of mind about almost everyone with whom we interact. Very often we may be left wondering what someone was thinking. For those people closest to us, though, our theories are detailed.

They help us understand who someone really is: how they feel, what they think, their beliefs, thoughts, loves, fears and so on.

In healthy brains, those two process are seamlessly integrated into coherent perceptions of others. Via mechanisms we don't quite understand, an individuals appearance is matched with our theory of mind about the other person, and we recognise them for who they are.

In some cases, though, the integration processes break down. When it does, someone can look and sound right but will not "seem" right in terms of their personality, in terms of who they really are.

This obviously is unsettling for the sufferer, confronted with someone they recognise but who seems not to be the person they remember.

In an attempt to reconcile that dilemma the brain comes up with a simple solution: the person is not who they claim to be, but rather an impostor, a body double.

This account might explain Timothy Murray's issues with Senator Lucas. If not – if the neuroscience is wrong – it might be time to call the Men in Black.

Explore further: Dreams, déjà vu and delusions caused by faulty 'reality testing'

Related Stories

Dreams, déjà vu and delusions caused by faulty 'reality testing'

February 19, 2014
(Medical Xpress)—New research from the University of Adelaide has delved into the reasons why some people are unable to break free of their delusions, despite overwhelming evidence explaining the delusion isn't real.

Targeting symptoms of psychosis

March 14, 2014
(Medical Xpress)—A novel psychological treatment to reduce the severity of delusional episodes experienced by people with psychosis is being trialled in a new Flinders University study.

Research advocates behavior-based treatment as an option for dementia patients

March 27, 2012
Dementia -- an acute loss of cognitive ability -- can be marked by memory loss, decreased attention span, and disorientation. It occurs in severe disorders such as Alzheimer's disease. Despite the fact that the condition ...

Heartbeats link mind and body together

August 15, 2013
While we're not necessarily aware of our heartbeat, this inner rhythm actually contributes to how we experience the body, and what belongs to it, according to research recently conducted at EPFL. A study to be published in ...

Study links brain activity to delusion-like experience

January 10, 2012
In a new study from the Centre for Addiction and Mental Health (CAMH), people with schizophrenia showed greater brain activity during tests that induce a brief, mild form of delusional thinking. This effect wasn't seen in ...

Recommended for you

Cognitive cross-training enhances learning, study finds

July 25, 2017
Just as athletes cross-train to improve physical skills, those wanting to enhance cognitive skills can benefit from multiple ways of exercising the brain, according to a comprehensive new study from University of Illinois ...

Brain disease seen in most football players in large report

July 25, 2017
Research on 202 former football players found evidence of a brain disease linked to repeated head blows in nearly all of them, from athletes in the National Football League, college and even high school.

Zebrafish study reveals clues to healing spinal cord injuries

July 25, 2017
Fresh insights into how zebrafish repair their nerve connections could hold clues to new therapies for people with spinal cord injuries.

Lutein may counter cognitive aging, study finds

July 25, 2017
Spinach and kale are favorites of those looking to stay physically fit, but they also could keep consumers cognitively fit, according to a new study from University of Illinois researchers.

Brain stimulation may improve cognitive performance in people with schizophrenia

July 24, 2017
Brain stimulation could be used to treat cognitive deficits frequently associated with schizophrenia, according to a new study from King's College London.

New map may lead to drug development for complex brain disorders, researcher says

July 24, 2017
Just as parents are not the root of all their children's problems, a single gene mutation can't be blamed for complex brain disorders like autism, according to a Keck School of Medicine of USC neuroscientist.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.