Detecting lies

Robin Hanson points to a list of methods for detecting lies:

1. Look for inconsistencies
2. Ask unexpected questions
3. Compare to when they truth-tell
4. Watch for fake smiles and emotions
5. Listen to your gut reaction
6. Watch for microexpressions
7. Are words and gestures consistent
8. Are they unusually uneasy
9. Watch for too much detail
10. Focus on the truths you find

In response, billswift comments that items 2,4,5,8,9 would be failed by autistic people, even if not lying.

I’d like to add to this that items 4,5,6,8 can be failed by people with Tourette’s syndrome, since an inability to look people in the eye is often taken as a sign of untrustworthiness (hence, flagging items 4 and 5), twitching can be taken as a sign of uneasiness (item 8) as well as allowing the observer to read in all sorts of microexpressions (item 6). After all, “shifty-eyed” people are liars, right?

More generally, the whole “gut reaction” thing can reinforce prejudice against anyone who behaves differently.

This is not to say that these lie-detection methods don’t work–I’d be interested in seeing the details of an empirical study–but it’s no fun being on the other end of this sort of appraisal.

P.S. In a comment on Robin’s blog, Anders Sandberg writes,

As for detecting lies, it is better to combine cues than look for individual cues. Aldert Vrij & Samantha Mann, Detecting Deception: The Benefit of Looking at a Combination of Behavioral, Auditory and Speech Content Related Cues in a Systematic Manner, Group Decision and Negotiation 13: 61–79, 2004
lists a variety of possible cues and talks about tests of detecting lies using them. They conclude that:

“there is growing evidence that CBCA scores, Reality Monitoring scores and some nonverbal cues, particularly illustrators and hand and finger movements are useful to look at. It sounds reasonable to suggest that the more these cues occur simultaneously in a person’s response, the more likely it is that the person is lying. Our own study (Vrij et al., 2000) showed that lie detection with each of the cues individually did not result in high hit rates. In other words, it is essential to work with multiple cue models.”

“The combined analyses revealed the most accurate classification of liars and truth tellers with a total hit rate of 81% (85% lie detection hit rate and 77% truth detection hit rate).”

One useful trick according to them is to compare the possible lie with a baseline of normal behavior for the person. But the method will only work if it is applied correctly, and they in particular point out the problems caused by making accusations that lead to biases in both the interviewer and interviewee. There is also a lot of widespread myths about individually reliable cues such as “liars look away” and “liars make many movements”, making many “expert” lie detectors actually worse than normal people at deception detection because they only look at single factors. The authors actually suggest a method to train away this bias, by having police either state whether people in a video are lying, or whether they have to think hard. Afterwards they can confront their scores and see that the thinking hard approach works much better.

8 thoughts on “Detecting lies

  1. The weirdest thing I see in that kind of approaches is that not only it assumes that there is a set of clues which will be good for all kind of lies and all kind of liars but ALSO that such a set of clues can be adequately mastered by anyone intent on spotting lies.
    Bad Scientism at its zenith, there is "one true way" and only one.

  2. Of course, even if it's true — and I think it probably is — that Hanson's list might fail consistently for autistics and Touretters, that doesn't mean it's not a "good" list in the sense of being useful for detecting lies: most people do not have autism or Tourettes, and in most people's lives the vast majority of lies that they hear will be told by people without these issues.

    On a different note: Some people are really good at lying. In many circumstances deception is acceptable or even encouraged (bluffing at cards, thanking people for gifts that you don't like, being nice to customers you detest, etc.) so people who are often in these situations get lots of practice at developing skills that make them seem sincere; presumably this practice might make them better at lying in other situations, though I don't know for sure that that is true.

  3. Phil,

    On your first point: yes, that is why in my entry above, I wrote, "This is not to say that these lie-detection methods don't work . . ."

    On your second point: yes, I imagine this has been studied. I think I'm a poor liar myself, and not even a good deceiver (which reduces my success in poker and, for that matter, chess), but I like to think that not being good at misdirection is actually in asset in scientific research and expository writing.

  4. I once heard a talk by Aldert Vrij (a specialist on lying, already mentioned above) – the gist of the talk was that actually all of points 2 to 10 surely are not very good for detecting liars (BTW, do you think that whoever put "listen to your gut reaction" on that list actually meant this seriously?). Vrij pointed out that some people actually get especially uneasy when they are telling the truth (point 8) or, because they have rehearsed their lies, have made up a very good story that sounds more consistent than would the truth. Some of his results are reviewed here:

    Instead of using very error-prone rules like those above, Vrij recommended asking detailed questions in order to find inconsistencies, so-to-say to detect a potential lie cognitively without looking for the rather unreliable emotional cues that make most of the 10 points in the list.

  5. I read a book called Lies Lies Lies by Charles Ford , which had a chapter on this subject. The thing that struck me most is that cops who all think they're good at detecting lies because they deal with liars every day are actually mediocre at it. It was the secret service agents that scored highest (around 80%). The author attributed their success to the fact that their day jobs involve screening a lot of people relentlessly without actually finding any bad guys.

  6. I think the key thing to detecting lies is overcoming psychological and social tendencies that enable liars. When a liar is about to get caught in an inconsistency, the other person will very often try to provide a possible explanation.

    For example, I threw a surprise anniversary party for my parents. My cover for the surprise was a family dinner for my birthday. I invited an old friend of theirs from Mexico, Tony, who they rarely talk with to the party. He accidentally called my mom to get the details for the party, and my mom convinced herself that he was inviting himself to my birthday dinner and not an anniversary party. The best part was after they walked into the surprise, her first response was: won't Tony be surprised when he gets here!

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