“A lie detector test is 100% accurate.”

The enduring belief in a device that can unfailingly expose a lie has roots stretching back to ancient times, with methods like the dry rice test in India assuming physiological reactions to deceit. The modern iteration, the polygraph, emerged in the early 20th century, with inventor John Augustus Larson creating a machine to measure multiple physical signals simultaneously. The press quickly sensationalized this invention, dubbing it a "lie detector," and its dramatic portrayal in books, high-profile criminal trials, and especially in countless movies and television shows, cemented the idea of its near-perfect accuracy in the public consciousness. Even the co-creator of Wonder Woman (Review), William Moulton Marston, contributed to this mythical aura with his "Lasso of Truth," having been involved in early lie detection efforts.

Despite its popular image, the scientific reality is far less conclusive. Polygraph tests measure physiological responses such as heart rate, blood pressure, respiration, and skin conductivity. The underlying theory is that lying causes distinct changes in these metrics. However, scientific consensus, including reports from the National Academy of Sciences, indicates that these physiological responses can also be triggered by anxiety, fear, anger, or even excitement, making it difficult to differentiate between genuine deception and other emotional states. There are no specific physiological reactions universally linked solely to lying, meaning a nervous truth-teller might exhibit similar responses to a deceptive individual. Landmark reviews have concluded that while polygraphs may detect lies at a rate better than chance, they have significant error rates, including false positives, and their scientific basis is weak.

The persistent belief in the polygraph's infallibility is fueled by several factors. Its continued use by some law enforcement and intelligence agencies for investigations and screening purposes, despite scientific reservations, lends an air of official credibility. Furthermore, polygraph examiners sometimes employ tactics to convince subjects that the machine is infallible, aiming to elicit confessions. The desire for a definitive, objective tool to uncover truth is powerful, and the dramatic, clear-cut depictions in media often override the nuanced scientific understanding of the polygraph's limitations.