When I was in my 20s I made carnival organs on the Greek Island of Crete. That statement may be a lie. How would you know?

A study just published in Psychological Science in the Public Interest discusses whether people can tell if someone is lying by observing their behavior or analyzing their speech. The authors state that the most important take-home message in their study is that detecting a lie is a difficult task because ” there is no nonverbal or verbal cue that lie detectors can truly rely upon.”

For instance, do you think you can tell a person is lying because he or she won’t look you in the eye or fidgets nervously. Not reliable cues say the authors, even though, “Overwhelmingly, both laypersons and professional lie catchers expect liars to act nervously.”

Another problem that can get  in the way of detecting a lie is that some people are just good liars.

Common traits of good liars

• Their natural behavior disarms suspicion – they smile, lean forward, look at you
• They don’t find it cognitively difficult to lie – they rehearse what they’ll say and how they’ll act
• They don’t experience emotions such as fear, guilt, or delight when they lie
• They are good actors and display a seemingly honest demeanor
• Their physical appearance may suggest virtue and honesty
• They are good “psychologists” – they have a sense of what people want to hear and how to say it convincingly

Sometimes, we’d rather not know if someone is lying to us because the lie may be more tolerable than the truth. But, what if you do want to know? Some of the techniques suggested by the study may be better used by professionals, but there are also some useful tips for the average truth-seeker.

How to catch a liar

• Ask questions in a way that is more information gathering than accusatory
  “What did you do yesterday between 3 pm and 4 pm” rather
  than “Your reactions make me think that you are hiding
  something.”
• Ask unexpected questions
  For example, asking “How old are you?” and following up with
  “What is the date of your birth?” should be harder for a liar to
  answer quickly
• Play the devil’s advocate
  Ask a question that compels the person to argue in favor of their
  personal view and then, playing devil’s advocate, ask a question
  that compels  them to argue against that view. People are more
  apt to have more to say about what they support
• Force them to think harder
  Lying is usually more mentally demanding than telling the truth,
  so the liar may be vulnerable to “cognitive overload.” Ask the
  person to repeat the story, but in reverse order, or insist on
  maintaining eye contact to hamper their ability to concentrate.

Lying has always posed a moral problem, say the authors, but could it also pose health problems? After reading the study, I  would have to venture a yes – at least for someone who gets tangled up in a web of deceit that makes them feel anxious, guilty, or worried.  Any of those feelings might  induce your body to secrete the hormone cortisol. Cortisol is sometimes called the stress hormone because it is commonly released when we’re under stress. It’s a normal and important hormone, but too much over too long a period of time is not a good thing.

Some negative health effects of too much cortisol

• Elevated blood sugar
• Elevated blood pressure
• Decreased thyroid function
• Lowered immune response

From personal experience, I believe telling the truth is definitely much better for your health. So, I confess. I did not make carnival organs in my 20s in Crete. I made them in a little village in the south of France.  In Crete, I  worked in a cucumber factory. I swear I did!

If you want to learn more about detecting lies, I recommend reading Pitfalls and Opportunities in Nonverbal and Verbal Lie Detection, the study that was just published in Psychological Science in the Public Interest.