Spotting Liars

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People’s unconscious reactions to liars and truth-tellers are more accurate than their conscious judgments.


Unconscious lie detection. I'm Bob Hirshon and this is Science Update. 

We might be better at spotting liars if we didn’t think about it. This according to Leanne ten Brinke and her colleagues at the University of California, Berkeley’s Haas School of Business. She says that humans are consistently terrible at distinguishing liars from truth-tellers. Her team’s study confirmed this—but also used an established test to gauge the participants’ unconscious reactions.

Ten Brinke:
We did find that there was some kind of discrimination happening here. The unconscious mind did seem to be able to pick out who was lying and who was telling the truth to them.

Why people ignore these gut reactions is a mystery. But ten Brinke notes that when consciously looking for liars, people often focus on behavioral cues like fidgeting or averting the eyes, even though there’s no evidence that these actually mean anything. I’m Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

Some people claim to know when they're being lied to. And in fact, armed with some knowledge about the person in question or the circumstances at hand, some people may be fairly good at it. But when asked only to determine if a stranger is lying or telling the truth, when absolutely no other information is available, people usually perform no better than they would flipping a coin. 

Ten Brinke and her colleagues were puzzled by this. She thought, for example, that there must be some value in knowing when people are being honest or not. She wondered if we do, in fact, detect lies on some level, even if we aren't aware of it.

In her experiment, volunteers watched videos of a fake “crime” interview. In all cases, the “suspects” insisted they hadn't stolen a $100 bill from a room. In fact, half of them had (and were told to do so). The viewers were asked to determine who was lying and who was telling the truth.

As usual, people were very poor at identifying liars and truth-tellers, hitting slightly below 50% accuracy in both cases. But the results were different when ten Brinke measured the volunteers' unconscious responses to the suspects. Using well-established tests (one of which is called the Implicit Association Test or IAT), the researchers examined the volunteers' tendency to unconsciously associate lie-related words like “dishonest” or “deceitful,” or truth-related words like “honest” or “valid,” with each suspect.

These unconscious associations (measured, for example, by the time it takes a volunteer to choose one type of word or another to describe the suspect) turned out to be more accurate than the volunteers' conscious judgments. According to the researchers, it appears that although we have some unconscious ability to detect lies, our conscious mind somehow overrides those judgments. 

It's not clear why this is. As you heard, it could be that when it comes to making conscious judgments, people rely on physical cues (like fidgeting) that we associate with lying, but aren't actually reliable. An interesting question for the future is whether people are more likely to act on their unconscious or conscious judgments. For instance, if you unconsciously sense that someone is lying about a theft but decide they're telling the truth, how likely would you be to leave your laptop alone in a room with that person? 

Now try and answer these questions:

  1. What is the difference between conscious and unconscious lie detection?
  2. What did the researchers find out about our accuracy in these areas?
  3. How did the experiment allow the researchers to test the volunteers' conscious AND unconscious judgments about the same people? Why do you think it was important to do so?

You may want to check out these related resources:

For other studies of lying and detecting lies, see the Science Updates Lying, Lying on Email, and Phone Fibbing.

The Science Update True or False explains why correcting falsehoods may sometimes, ironically, make people believe them more.

Going Further

For Educators

For other studies of lying and detecting lies, see the Science Update lessons LyingLying on Email, and Phone Fibbing.

The Science Update lesson True or False explains why correcting falsehoods may sometimes, ironically, make people believe them more.

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