Can Lying Really Make You Vomit? The Truth about Lying and What It Does to the Body

(This is a spoiler-free article about an unusual medical condition seen 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…