• March 2016

Neuroscience Shows Why We Can’t Always Spot Liars

By Carol Goman

A short time after “The Truth About Lies in the Workplace” was published, I received this email: “I had just begun reading your book, and had gotten to the part about body language signs that point to someone who is lying when I was confronted with a real life situation.

A parcel (that was meant to be returned) disappeared from my office. When I questioned the delivery man, he gave off at least three of the body language signals that said he was lying. As I watched him, I thought – ‘No way! He wouldn’t do that.’ Later, he was captured on video by one of the surveillance cameras leaving the building with the package.”

So, if you know what to look for, if you have a list of the “right signals,” lie detection is easy, right?

Not always.

Some people (like the delivery man) subconsciously display the telltale signs of deception that make their lies relatively easy to spot — but other liars are much more elusive. Neuroscience has been looking into what happens in the brain to explain this difference.

One researcher, Tali Sharot, a cognitive neuroscientist at University College in London, found that the brains of people who are unused to lying show a huge response in regions involved in emotion – like the amygdala and the insula – when they tell a falsehood. But, as a person lies more frequently, the emotional response lessens and the negative feelings associated with lying dissipate. Habitual and pathological liars can become quite comfortable with their falsehoods.

Most of the observable signs of lying are dependent on the liar feeling a negative emotional arousal and an uncomfortable sense of conflict. In those cases, the act of lying triggers a heightened stress response. Blood pressure, heart rate and breathing rates all increase, and this gets displayed in a variety of “tells” such as:

  • Fake smiles. It’s hard for liars to give a real smile while seeking to deceive. (Real smiles crinkle the corners of the eyes and change the entire face. Faked smiles involve the mouth only.)
  • Unusual response time. When the lie is prepared before questioning, deceivers start their answers more quickly than truth-tellers. If taken by surprise, however, the liar takes longer to respond – as the process of inhibiting the truth and creating a lie takes extra time.
  • Unnecessary elaboration. The more someone embroiders a story, adding unnecessary details and irrelevant information, the greater the chance he or she is trying too hard to convince, rather than to convey facts.
  • Greater formality. A liar’s language tends to become awkwardly formal and stilted, characterized especially by the avoidance of commonly used contractions. A liar might say, “I did not have sex with that woman, Ms. Lewinsky,” rather than, “I didn’t have sex with Monica.”
  • Higher vocal pitch. When lying, a person’s vocal tone will rise to a higher pitch. Other verbal cues include rambling, selective wording (in which one avoids answering the question exactly as asked), stammering, and the use of qualifiers.
  • Change in blink rate. A person’s blink rate slows down as she decides to lie and stays low through the lie. Then it increases rapidly (sometimes up to eight times the normal rate) after the lie.
  • Nose touching. A person’s nose may not grow when he tells a lie, but watch closely and you’ll notice that when someone is about to lie or make an outrageous statement, he’ll often unconsciously rub his nose. (This is most likely because a rush of adrenaline opens the capillaries and makes his nose itch.)
  • Changes in gestures. Often times, in the effort not to let their gestures “give away” the lie, deceivers will hold their bodies unnaturally still. At other times, especially after being asked a searching question, you may notice liars accelerate pacifying gestures — biting their lips, rubbing their hands together, fidgeting with jewelry, touching their hair.

But what about psychopaths or those practiced deceivers who become comfortable with the act of lying? Or those who over time begin to believe their own lies? Whenever someone has “neutralized” the negative emotional responses that accompany lying, it interferes with your ability to spot deception.

The polygraph, the most widely used method for lie detection, monitors heart rate, blood pressure, and skin conductance to detect the increased anxiety that often accompanies a lie. But one of the reasons that polygraph results are inadmissible in court (and why it is difficult to spot some deceivers in action) is that lie detectors fail with people who are not anxious about lying. These are the same liars who can most easily fool you.

Learn more at CarolKinseyGoman.com.