Ulterior Motives

How goals, both seen and unseen, drive behavior

Can You Tell When Someone Is Lying?

The best way to find a liar is not to try.

I love movies about con artists.  David Mamet’s early film House of Games is a great example.  Throughout the film, it is hard to tell who is lying and who is telling the truth.   The success of movies like this is that it is often difficult to be certain that someone is lying to you. 

Over the years, many studies have demonstrated that people are not that good at determining when someone is lying to them.  Part of the problem is that there are no obvious cues that separate lying from truth telling.  Another part of the problem is that we often use the wrong cues.   So, people often focus on whether someone is moving their body in a nervous way or averting their gaze when speaking, but those characteristics are not good cues to whether someone is lying.

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That does not mean that it is impossible to judge whether someone is lying.  A paper in the November, 2013 issue of the Journal of Personality and Social Psychologyby Marc-Andre Reinhard, Rainer Greifeneder, and Martin Scharmach explored how different types of thought affect accuracy at lie detection.

Often, we solve problems and make judgments with conscious thought.  If I ask you whether a particular person is lying to you, you might spend some time thinking about your interaction and then make a judgment. 

Sometimes, though, you engage in unconscious thought.  You know you have a problem to solve or a judgment to make, but you walk away from the problem and work on other things.  Then, you come back to the problem.  In those cases, you find that you are now thinking about the problem in a different way. 

The researchers suggested that people might be more accurate at detecting liars after unconscious thought than after conscious thought.  The idea is that unconscious thought may be able to take more characteristics of an interaction into consideration than conscious thought does.  In addition, unconscious thought may capture aspects of an interaction that would be hard to isolate when thinking consciously. 

In one study, participants watched videos of people who either told truthful stories about an event that happened to them, or they lied.  One group made a judgment after each video about whether the person was telling the truth.  A second group watched the entire set of videos and then was asked to think about each video consciously for several minutes and then to judge whether that person was telling the truth.  A third group watched the entire set of videos and then was told they would be judging whether the individuals told the truth.  After that, they engage in a difficult distracting task for several minutes so that they could not consciously think about their judgments.  Then, they judged whether the speakers were telling the truth. 

The participants who made immediate judgments and those who had a chance to deliberate consciously had difficulty determining who was telling the truth and who was lying.  The participants who engaged in unconscious thought were much better at this task and were able to identify the truth tellers and liars about 65% of the time.  That is not perfect, of course, but it is better than random guessing.

In these studies, how can you tell whether the improvement comes from actual unconscious thought or whether it is just a result of being distracted for a while after hearing the people? 

For unconscious thought, the individual needs to be pursuing a goal (like determining whether the person is lying).  In one study, participants observed people who were either telling the truth or lying.  Some were told to deliberate consciously about whether the person was telling the truth.  Some were told that they were going to judge whether the people were telling the truth and then were given a distractor task until it was time to make the judgments.  A third group did the distractor task without being told anything about determining whether people were telling the truth.  Then, they made the judgments.  Only the group that was told they were going to make judgments and then were distracted were reasonably good at separating the liars from the truth-tellers.   So, it appears that unconscious thought rather than mere distraction is affecting people’s judgments.

In one final study, participants were exposed to a large number of videos of people telling the truth or lying.  These videos were carefully coded for a variety of cues like the number of details included in the stories, how much eye contact people made, and the amount of tension in the voice.  Analyses of these cues were done against whether the person was actually telling the truth.  Many of the cues (like eye gaze) were not at all correlated with whether the person was telling the truth.  Some (like facial pleasantness) were reliably associated with telling the truth.  Others (like vocal tension) were reliably associated with lying.

In this study, some participants judged whether the speakers were telling the truth immediately.  Some engaged in conscious deliberation.  Others engaged in an unconscious thought condition.  As before, those in the unconscious thought condition did a better job of separating the truth-tellers from the liars.  Statistical analyses were used to determine what cues the groups used to make their judgments.  Participants in the control and conscious thought conditions tended to pay attention to cues that are easy to detect like eye gaze that are not actually correlated with whether people were telling the truth.  Participants in the unconscious thought condition were much more likely to use cues like vocal tension and the length of pauses in speech that are actually associated with lying.

Putting this all together, it is clear that it is very hard to determine whether someone is lying to you.  If you are concerned about trying to make a judgment about lying, though, you should give yourself a little time away from the interaction before coming back to make the judgment.  That will improve your odds of figuring out whether you were being lied to.

Of course, if you are really worried you are being lied to, perhaps you need to spend time with a different group of people.

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Art Markman, Ph.D., is a cognitive scientist at the University of Texas whose research spans a range of topics in the way people think.

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