The Truth About Lie Detectors

With the possible exception of politicians and small wooden puppets named Pinocchio, most people have a hard time lying with a straight face—and an even harder time lying successfully when their every move, breath, inflection of speech, and variation in blood pressure is being monitored.

While the accuracy of the modern lie detector, or polygraph machine, is considered dubious by many researchers—in 2002, the National Academy of Sciences determined the polygraph to be essentially useless—it's popularly believed that a simple machine can really determine whether or not a person is telling a lie.

Of course, we've bought into a lot of crazier ideas in centuries past. In medieval England, a person thought to be lying might be subjected to a test of fire (walking across hot stones; carrying a scorching hot iron rod) or water (being tossed into the pond). If a person was burned in a trial by fire, it was considered sufficient evidence for a hanging. A person tried by water had an even worse deal: if you floated, you were guilty, and sent to the hangman's noose. If you sank, you were considered innocent, but since you were dead from the drowning, it didn't make too much of a difference.

Untruth or Consequences

By the 19th century, governments were no longer throwing people in ponds (not as a measure of truth-telling, anyway), but the methods used to assess a person's character were still pretty dubious. Phrenology—the study of bumps on the skull—and the new discipline of psychology gave rise to the idea that physical characteristics and behavior could demonstrate a person's moral character, and thus their truthful or deceitful nature.

In 1895, Cesare Lombroso theorized that sudden changes in a person's blood pressure could be an indication of lying, and he attempted to chart these changes with a device called "Lombroso's Glove." More sophisticated machines—simultaneously recording blood pressure, pulse, respiration, and galvanic skin response—were later developed by Dr. John A. Larson and Leonard Keeler (widely considered the father of the modern polygraph machine) in the late 1920s and early 30s. But it was a psychologist named William Marston who first popularized the "lie detector," and gave it the cultural prominence it has today.

Lasso of Truth

Marston was hired by the US government during WWI to come up with a way to make sure that prisoners of war told the truth during interrogation. Echoing Lombroso's experiments, he decided to test his subjects' blood pressure during their interviews. In 1917, he published his findings to great acclaim in the press, who hailed him as the inventor of the "lie detector." Marston didn't shy away from the title. In fact, he publicly stated that his discovery hailed "the end of man's long, futile striving for a means of distinguishing truth-telling from deception."

A tireless advocate for truth, Marston was undaunted by the court's ruling. Instead, his obsession with honesty would later fuel his work in creating the most enduring female superhero in comic book history, and the greatest lie detector of them all—Wonder Woman, whose magical golden lasso compelled villains caught inside it to tell the absolute truth.

This article was written by Ransom Riggs and excerpted from the mental_floss book In the Beginning: The Origins of Everything. You can pick up a copy in our store.

Speaking of Lie Detecting... We recently released our first iPhone trivia game. You're given two statements "“ one true, one blatantly false. Your job is to spot the Big Fat Lies! If you've got an iPhone (or iPod Touch) and $2.99, head on over to the iTunes Store and get downloading. (That link should open up your iTunes and send you right to Big Fat Lies! page of the store. If not, you can search for "Big Fat Lies" and it will come right up.)