Why Lies Fail – Part 1

This is the first part in a series on why lies fail. Read part 2 here.

Why Lies Fail

When asking why lies fail, it’s important to remember this:

Not all do.

• “Can’t talk now, just on the way out the door”.
• “I love your new dress.”
• “What a great evening, thanks so much.”
• “Sorry, couldn’t get a babysitter.”

Sound familiar? These are lies that often succeed, because we want to protect ourselves or other people—and because it would be rude if the target of our lie challenged whether the truth was being told or not.  

On the other hand, there are certainly times when our lying fails.

Which lies fail?

Instead of asking why lies fail or succeed, turn your attention to which types and circumstances of lies tend to fail:

• Serious lies: When a lot is at stake—such as when a valued reward stands to be lost and punishment will be delivered if the lie is uncovered—there is a chance that the liar’s demeanor will betray the lie and it will fail.
• Emotional lies: Lies about a strong emotion felt right in the moment are the hardest to tell successfully. It doesn’t matter which emotion is denied: anger, fear, disgust, contempt, excitement, enjoyment, sadness, or surprise. Each of these emotions generates involuntary changes in facial expressions, voice, gaze, and posture. Most people cannot deliberately inhibit or cover every manifestation of an emotion when it is felt strongly. The emotional load—the burden of trying to conceal any sign of the emotion that is churning away—interferes with the ability to speak coherently and convincingly, so that the words spoken may also betray the lie and it fails.
  • Many lies are not about emotions felt in the moment; rather, they conceal a past action, plans for a future action, thoughts, attitudes, or values. If the discovery of the lie could result in punishment, then the liar will have emotions about engaging in the lies. These feelings about lying will generate involuntary changes in demeanor that can betray the lie and cause it to fail.

Which lies succeed?

Of course, some types of lies do typically work, such as trivial lies. These types of lies succeed because nothing is at stake, the liar doesn’t expect to be questioned, and doesn’t fear being caught. If by accident the target later finds out that the truth had not been told, or what had been said was an excuse or flattery, then no harm done.

Research shows that it is easy to tell such trivial lies precisely because nothing much is at stake, so there will be no clues to deceit in demeanor. Of course, many lies—trivial or serious—are detected not from what the liar said or how he or she said it, but from other sources unrelated to the liar’s demeanor. A witness observes a violation of the lie, or some physical evidence (lipstick on the shirt collar), for example.

Learn More 

For more information, be sure to read Why Lies Fail—Part 2 or take our lying quiz to see how well you can detect deception.