(This is a spoiler-free post about an unusual medical condition portrayed in the movie Knives Out.)
In the hit film Knives Out, Detective Benoit Blanc is hired to investigate the mysterious death of a wealthy novelist named Harlan Thrombey. Blanc questions the members of Thrombey’s eccentric family and his nurse, Marta Cabrera.
When Marta admitted, “Just the thought of lying makes me puke,” she was not kidding. Marta is like Pinocchio, but instead of lies elongating her nose, they make her vomit. Marta’s strange reflex is a dream for a private investigator trying to uncover the truth, but could such a biological anomaly actually exist off the movie screen?
What happens to the body when we lie?
We tell lies all the time. A 2002 study performed by psychologist Robert Feldman at the University of Massachusetts found that 60 percent of people lied at least once during a 10-minute conversation, telling an average of two to three lies.
The tendency to lie is deeply rooted in our evolutionary history, as other primates have been observed to cheat and deceive. Human children pick up this crafty behavior between the ages of two and five, and it is seen by some psychologists as a milestone of cognitive growth.
Many lies are trivial and are told simply to keep the peace or make someone feel good. Examples include niceties such as “You can’t tell that you’re wearing a toupee!” or “The turkey doesn’t taste dry to me!”
But more sinister lies, such as falsely accusing someone of a crime or lying to investors, can have devastating consequences. Dishonesty puts the brain in a state of heightened alert, and this stress increases with the magnitude of the lie.
Why does the brain care about honesty? As social animals, our reputation is paramount. Consequently, most people work very hard to maintain an image of trustworthiness and integrity.
Knowing that dishonesty risks irrevocable damage to one’s reputation, lying is an inherently stressful activity. When we engage in deceit, our respiratory and heart rates increase, we start to sweat, our mouth goes dry, and our voice can shake. Some of these physiological effects form the basis of the classic lie-detector (polygraph) test.
People vary in their ability to tell a lie due, in part, to differences in the brain. To take an extreme example, sociopaths lack empathy and therefore do not exhibit a typical physiological response when lying. Liars can also pass a polygraph if trained to stay calm during the test. Similarly, innocent people may fail the test merely because they are anxious about being hooked up to the intimidating equipment. For these reasons, the accuracy of polygraph testing is heavily contested.
In contrast, brain imaging studies are proving to be much more informative for learning about the body’s response to lying. Symptoms of anxiety arise because lying activates the limbic system in the brain, the same area that initiates the “fight or flight” response that is triggered during other stresses. When people are being honest, this area of the brain shows minimal activity. But when telling a lie, it lights up like a fireworks display. An honest brain is relaxed, while a dishonest brain is frantic.
Short-term and long-term effects of lying on health and well-being
Two doctors were recently questioned about Marta’s peculiar reaction to lying. Speaking to Fast Company, gastroenterologist Kara Gross Margolis of the Columbia University Medical Center stated that she has never seen a patient that suffers from chronic vomiting after lying. Nor has David A. Johnson, a gastroenterologist at Eastern Virginia Medical School. Speaking to Slate, Johnson said, "Never, at least in my 42 years of experience, has it [chronic vomiting] been brought up that it was specifically around a lie."
However, both experts mention the so-called gut-brain axis as a plausible mechanism behind a regurgitative reflex. The gut-brain axis refers to the two-way communication that takes place between these two bodily systems, explaining why we sometimes get butterflies in our stomach when nervous. Kara Gross Margolis admits that “significant anxiety can lead to nausea and vomiting,” opening the door for such a condition to exist in someone who is constantly worried.
Deception Essential Reads
Look at People's Hands to Determine Veracity
Pacifying Gestures May Indicate Deception
In addition to short-term stress and discomfort, living a dishonest life would seem to take a toll on health. According to a 2015 review article, constant lying is associated with an array of negative health outcomes including high blood pressure, increased heart rate, vasoconstriction, and elevated stress hormones in the blood.
Other studies suggest that long-term effects could be minimal since it appears that we get more comfortable with lying the more we do it. In other words, we develop an unsettling tolerance to being devious.
Brain imaging experiments conducted by Tali Sharot at University College London show that the brain adapts to dishonest behavior. Participants showed reduced activity in their limbic system as they told more lies, supporting the idea that each lie makes lying easier. In addition, the findings support the adage that small acts of dishonesty can escalate into larger ones. If true, Marta’s tendency to vomit after lying could diminish over time as her brain adapts to being dishonest.
If our brain can cozy up to lying with enough practice, it would explain society’s disdain for dishonesty and why people hesitate to give liars a second chance. These strong social rules and the penalties that come from breaking them might be what really keeps us honest at the end of the day.
As a seasoned expert in neuroscience and psychology, I delve into the intriguing topic of lying and its potential physiological effects on the human body, inspired by the unusual medical condition portrayed in the movie Knives Out. In the film, the character Marta Cabrera experiences a unique reflex where lying induces vomiting, akin to Pinocchio's nose elongating when he tells falsehoods.
The concept of lying and its consequences is deeply rooted in human behavior and evolution. Research, such as the 2002 study by psychologist Robert Feldman at the University of Massachusetts, indicates that lying is a prevalent aspect of human communication, with individuals telling an average of two to three lies in a 10-minute conversation. This tendency to deceive has evolutionary roots, observed in other primates and emerging as a cognitive milestone in human children between the ages of two and five.
The article explores the physiological responses to lying, emphasizing the heightened stress and alertness associated with dishonesty. Dishonesty triggers physiological reactions such as increased respiratory and heart rates, sweating, dry mouth, and shaky voices. These effects form the basis of traditional lie-detector tests (polygraphs), though their accuracy is heavily contested.
The piece also touches on individual differences in the ability to lie, citing sociopaths as an extreme example who lack the typical physiological responses associated with deception. Brain imaging studies are presented as a more informative tool for understanding the body's response to lying, revealing increased activity in the limbic system during dishonesty.
Moving on to the portrayal of Marta's chronic vomiting after lying in Knives Out, the article consults two gastroenterologists, Kara Gross Margolis and David A. Johnson. While they haven't encountered patients with a similar condition, they suggest the gut-brain axis as a plausible mechanism. The gut-brain axis involves two-way communication between the gut and the brain, and anxiety is proposed as a potential trigger for nausea and vomiting in response to deception.
The long-term effects of lying on health are explored, referencing studies that associate constant lying with negative outcomes such as high blood pressure, increased heart rate, vasoconstriction, and elevated stress hormones. However, the article also notes that individuals may develop a tolerance to lying over time, as demonstrated in brain imaging experiments by Tali Sharot at University College London.
In conclusion, the article speculates that Marta's unusual reflex could potentially diminish over time as her brain adapts to dishonesty. This leads to a broader discussion on societal attitudes toward dishonesty, emphasizing the importance of social rules and penalties in maintaining honesty within a community.
