How to spot a liar

By Gary Plank

A few simple truths:

  • We’ve all been lied to.
  • We’ve all made the mistake of believing lies.
  • And we’ve all made the mistake of disbelieving truth.
  • Having believed lies rightly makes us skeptical. Having disbelieved truth should also make us humble and diligent in our quest for understanding.

Keep these things in mind as you try to gauge other people’s truthfulness.

Establish a baseline.

To understand if someone is being truthful, we must know how that person normally communicates in similar circumstances. Once we have a baseline for truthful discourse, we can watch for deviations from that baseline and better understand areas of stress.

Avoid confirmation bias.

We must remain open to all possibilities as we listen. We must be skeptical when information doesn’t seem to fit together. But if we’re not also skeptical of our own hunches, we leave ourselves open to confirmation bias— that human tendency to see only the evidence that fits our notions of what’s true. In criminal investigations, confirmation bias can imprison the innocent and free the guilty. In our personal lives, confirmation bias can cause its own problems.

Don’t misread the signs.

The signs we detect in conversations may be real, but we often misread them. For example, in some cultures it’s respectful to avoid eye contact when speaking to an authority. The old belief that a man who won’t look you in the eye is lying must make room for the truthful man who looks away to show deference. Likewise, we often read closed body language as a sign of distancing or dishonesty. My experience with rape victims has shown how unreliable an indicator of deception closed body language can be. Rape victims and others who’ve suffered trauma will often feel vulnerable. They’ll naturally display closed body language, even when being truthful.

Detect stress. Trust evidence.

Most of the so-called “signs of deception” are actually indicators of stress. (Polygraphs don’t detect lies. They measure physiological responses to stress.) When investigators see signs of stress during questioning, they don’t automatically conclude they’re being lied to. They recognize the topic being discussed might be a source of stress and therefore be worthy of further investigation. Indicators of stress may come to light through unimportant topics that are over-explained or important information that is glossed over or simply omitted.The easiest way to deceive is to omit. This is the most common tactic employed by deceptive individuals. Investigators are wise to let the evidence of that investigation—as opposed to hunches or unreliable signs—determine what is and is not true.

Be honest with yourself.

Recognize what you do and do not know about the events being described. And recognize that the methods behavioral scientists use to investigate crimes may not be well suited to your personal life. Even if it uncovers something interesting, it’s almost never in your interest to subject your spouse, for example, to a tactical interrogation. My best advice: Don’t try this at home.

Gary Plank is a retired criminal investigator and heads the behavioral science track of Nebraska Wesleyan’s Forensic Science Program.