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6 Reasons Why It's So Hard to Be Sure That a Partner Is Lying

There are many reasons why humans are generally very poor lie detectors.

Key points

  • Both successful lying and successful detection of lies are highly-developed social skills.
  • Often people rely on inaccurate nonverbal cues associated with lying.
  • Research suggests that people may trust too much. A person's ability to detect deception may be affected by cognitive biases.
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Trying to tell if a stranger is lying to you is difficult enough, and we may think it’s easier to tell if someone close to us is lying. However, there are many reasons why humans are generally very poor lie detectors. Here are the main reasons lie detection is so difficult and why we might not be able to tell if our loved one is lying to us.

  1. Trusting Bias. Research clearly shows that we trust others too much. Even in studies where people are told that they will see 50% lies and 50% truths, they judge well more than half as “truthful.” This trusting bias may be even stronger with people whom we love. In general, when it comes to everyday interactions with those close to us, we tend to give them the benefit of the doubt.
  2. Crossing the Line. It is uncomfortable and seems impolite to accuse someone of lying. So, our sense of decorum and social etiquette often keeps us from being overly suspicious. And, without being able to cross-examine the potential liar, it makes the lie more difficult to detect.
  3. Relying Too Much on Inaccurate Cues. Our research clearly shows that people tend to rely too much on stereotyped cues of deception. For example, it is a common belief that a liar can’t look you in the eye. Yet, our research found that people engaged in more eye contact when lying than when telling the truth. Why? Likely because they knew that lack of eye contact would be a giveaway. [My wife is sure that when my tone of voice gets higher, it means I’m lying. It doesn’t!].
  4. Differences in Motivation. A lying partner may be more motivated to deceive successfully. Unless there are grounds for suspicion, the other person may not be particularly motivated to try to test the veracity of their partner’s story.
  5. Differences in Skill. Lying successfully is a skill that can be developed over time. Your partner may be a more skillful liar than you are a detector of lies. In fact, there is good evidence that even people who are trained to detect lies better don’t get that much better at it. Good liars tend to have the upper hand.
  6. You Fear the Consequences. Many times, in relationships, an individual may not want to test their partner’s honesty because there can be severe consequences. The partner may become angry. It may drive a wedge between the couple. In some instances, not knowing may be a more comfortable alternative.

So, what cues are the best indicators of truth or deception? Despite the belief that the most reliable cues of lying are nonverbal, our research suggests that when it comes to the veracity of another’s story, the most accurate cues were verbal and included how plausible the story was.

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Riggio, R.E., & Friedman, H.S. (1983). Individual differences and cues to deception. Journal of Personality and Social Psychology, 45, 899-915.

Riggio, R.E., Tucker, J.S., & Throckmorton, B. (1987). Social skills and deception ability. Personality and Social Psychology Bulletin, 13, 568-577.