Over the years, CIA agents, police detectives, psychologists, lawyers and others have tried a variety of methods to identify liars, from polygraph machines to "voice stress analysis" to analysis of barely perceptible facial movements that can give away hidden feelings. None of the techniques has been foolproof.
And the search for the truth continues. The science of liars and lying remains a hot topic in research circles, and book after book offers the latest theory about how to tell when a spouse is cheating, a witness is lying in court or a car salesman is overstating the value of a vehicle.
A person's eyes tell the truest story.Looking at someone in an unwavering manner and answering the question is very telling. When I see eyes shift side to side and up and down, it just causes suspicion.
Hartley, the former interrogator, agrees that body language can hint at deception. But not always, he says. "Your eyes drift naturally when you're searching for information," he says. "I've never met anyone who doesn't move their eyes when looking for details."
The key to uncovering a lie, he says, is knowing how the liar behaves normally, when he or she is relaxed, and picking up on changes in voice patterns, eye movement and other body language.
"You've got to ask the right questions, then observe how that person responds," Hartley says.
Signs of stress, which may signal that someone is lying, include flared nostrils and audible breathing, shaky hands and elbows moving closer to the ribs, according to Hartley.
"Stress does horrible things to our brains," he says. "Stress hormones can virtually turn off your brain and make you become reactive."
For the most notorious liars, the tendency to fib may be biological, suggests a study by researchers at the University of Southern California.
Pathological liars, the scientists found, have structural differences in their brains that could affect their abilities to feel remorse and learn moral behavior and might give them an advantage in planning deceitful strategies, the researchers discovered.
Types of lies
Joseph Tecce, an associate professor of psychology at Boston College who has studied liars and lying, identifies six types of untruths, some more egregious than others.
He classifies them as:
The 'protective' lie, which can shield the liar from danger.
The 'heroic' lie, created to protect someone else from danger or punishment.
The 'playful' lie, such as an angler's fib about the size of his fish.
The 'ego' lie, designed to shield someone from embarrassment.
The 'gainful' lie, which somehow enriches the fibber.
And the 'malicious' lie, told to deliberately hurt someone else.
Other scientists have suggested that pathological liars owe their behavior to the psychiatric diagnosis known as narcissism, and may truly believe their own falsehoods.
