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The Science of Lie Detection

Lying has always been a popular topic for exploration, especially in the entertainment industry. It is very common to see crime shows in which an alleged perpetrator is hooked up to a polygraph machine to determine his truthfulness, or lack thereof. A few years ago, a TV show called Lie to Me hit the airwaves. The show is based on the work of Dr. Paul Ekman, a scientist and author best known for furthering our understanding of nonverbal behavior. Actor Tim Roth plays Dr. Cal Lightman, a scientist and lie detection expert who uses facial expressions and body language to determine whether someone is lying.

Surveys have shown that the average person lies at least once a day, with college students lying as much as twice a day. Since dishonesty is encountered on a daily basis, lying should be easy to identify; however, this is far from the case. Attempts to deceive others in everyday life are as difficult to detect as they are common and, contrary to what’s depicted in Lie to Me, a large body of research reveals surprisingly few valid cues of deception.

Psychologist William Moulton Marston invented the first lie detector in the 1920s. Interestingly, Marston’s invention led to the creation of Wonder Woman, the female superhero who could compel people to tell the truth using her magic lasso. Marston’s invention became the prototype for modern lie detectors, which record on a chart physiological activity such as skin conductance, blood pressure, and respiration. Although physiological activity may offer helpful clues to identify lying, the lie detector is far from infallible.

The polygraph excels at determining increasing anxiety or nervousness, but does a poor job of pinpointing the reason for the anxiety, which may or may not be due to lying. Rather than a “lie detector,” the polygraph may more accurately be described as an arousal detector. On Lie to Me, Dr. Lightman demonstrated how the lie detector test can be manipulated. In the first case, he gave a witness valium and then had her deliberately lie while hooked up to the machine. However, because of her tranquility, the reading indicated that she was telling the truth. In the second case, Dr. Lightman asked a male witness an identical set of questions using two different administrators. The witness answered truthfully each time. When the questions were asked by a man, the machine indicated the witness was telling the truth, but when the questions were asked by an attractive woman, the machine indicated the witness was lying. His attraction to her raised his anxiety levels.

While Lie to Me is accurate about the unreliability of lie detectors, it isn’t as easy as the show makes it appear to read facial expressions and body language to determine honesty. Even people trained in the criminal justice field such as judges and police officers can’t always identify if someone is lying. While there are no conclusive clues that indicate deception, honing skills of observation is still helpful, as people often do provide signs that they are being untruthful.

What do you think? Can lying ever be perfectly identified? PAR wants to hear from you, so leave a comment and join the conversation!

 

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