How do you spot a liar? Scientists say it's trickier than you might think
EMILY KWONG: You're listening to Short Wave from NPR.
REGINA BARBER: Hey, Short Wavers. It's Regina Barber.
KWONG: And Emily Kwong. OK, so between the two of us, I feel like you love TV more.
BARBER: Yes, that's absolutely true. It was my first and, for the longest time, my only friend.
KWONG: And now we're friends, so that's cool.
BARBER: Yeah, now I have two.
KWONG: [LAUGHS] But I recently found myself going down a TV rabbit hole. It's technically a reboot of a reality classic, The Mole--
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SPEAKER 1: Welcome to Malaysia.
KWONG: --where players are working together as a team to carry out a series of missions--
SPEAKER 2: We have no hints. --for the prize money in a pot that only one of them can win.
SPEAKER 3: So you chose the cash, right?
SPEAKER 4: I 100% chose the cash.
KWONG: Within their ranks is a mole--
SPEAKER 5: Go, go, go, go.
SPEAKER 6: Yes.
SPEAKER 7: Hold on.
SPEAKER 8: Ugh!
SPEAKER 9: Anyone could be the mole.
KWONG: --someone hired by to sabotage the team.
SPEAKER 10: Should the players trust me?
SPEAKER 11: No.
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BARBER: So this is like The Amazing Race meets Among Us.
KWONG: Yeah, but it's not on a spaceship. This--
BARBER: Boo.
KWONG: --show is set in the real world.
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BARBER: That's cool.
ARI SHAPIRO: I'm Ari Shapiro, and I'm going to be your guide for this incredible adventure.
SPEAKER 12: Woo!
SPEAKER 13: Woo!
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BARBER: Shout-out to our news roundup buddy, Ari. He hosted this season.
KWONG: It's our very Ari. I was so proud.
BARBER: Yeah.
KWONG: And I had to ask him-- before hosting the show, did you consider yourself someone who was good at spotting a liar?
SHAPIRO: Absolutely not, and I still don't.
[LAUGHTER]
SHAPIRO: I do not think I got any better at it in the course of the show.
BARBER: Tell me about that psychological unraveling for you.
SHAPIRO: 'Cause people can be nervous for all kinds of reasons, having nothing to do with the fact that they're lying.
BARBER: Yeah, I mean, I am a terrible liar. I just cannot do it.
KWONG: But would you say you're good at spotting a liar?
BARBER: Um, I think after all these years, I'm actually better at it, but I'm still not good.
KWONG: Gina, you are not alone. There's this thing called truth default theory, developed by Tim Levine at the University of Alabama at Birmingham. He suggests that in communication, honesty is the default, and people tend to believe each other.
TIM LEVINE: Because humans are social, and everything in our lives wrap around us being able to communicate and convey information to one another.
KWONG: But if there is a reason for people to lie, they do. So there's a whole body of lie detection and deception research spanning multiple scientific fields. And when I told Ari this, he lit up at the thought, and he gave me, like, an assignment.
SHAPIRO: I want a playbook. I want some scientist to tell me what do I need to do to figure out who the liar is.
KWONG: OK.
SHAPIRO: Like, very nuts and bolts, checklist, follow these guidelines.
KWONG: OK.
BARBER: I mean, I love his, like, faith in science, for one. I like that he wants this playbook of spotting a liar.
KWONG: Yeah. But I also wondered, does a lie detection playbook even exist?
BARBER: Right. So today, on the show, Emily goes down The Mole hole of deception research to discover how lie detection has changed and determine if it's even possible to catch a liar in the act. You're listening to Short Wave, the science podcast from NPR.
BARBER: OK, Em, where do you want to start here?
KWONG: I want to start with the polygraph.
BARBER: The machine used for lie detection.
KWONG: Yeah, and oddly, the early inspiration for it was a medical device to record vital signs, so a patient's, like, pulse or blood pressure.
BARBER: I mean, that kind of makes sense. But, I mean, that's not for interrogation at all. It's not an interrogation tool.
KWONG: No, no. That happened around 1921 at the Berkeley, California, Police Department. A rookie cop and physiologist named John Larsen got hold of a psychology paper by William Moulton Marston.
BARBER: OK, I think I know this guy. William Marston also created Wonder Woman, right, and her Lasso of Truth.
KWONG: Yeah, he was a little obsessed with, like, sussing out who was lying, and he thought there was a link between vital signs and emotions, and that a machine, the polygraph, could prove that.
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SPEAKER 14: Dr. William Marston demonstrates a complicated device whereby he claims he can determine and compute comparative emotions of blondes, brunettes, and redheads.
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KWONG: Now, Gina, the science to back up Marston's claims was scant, but at the time, it was convincing enough for the Berkeley Police chief, who saw an opportunity.
KEN ALDER: He wants to make the police themselves more law abiding, give them science, instead of violence, as a tool. And the lie detector fits into that program because he wanted to change the way interrogations took place.
BARBER: Hmm, interesting.
KWONG: Yeah, this is Ken Alder. He is a historian at Northwestern University, wrote a book about the history of the polygraph. He says its use as an interrogation device started in Berkeley, but it then spread to police departments around the country and into the commercial sector. So by the '60s and the '70s--
ALDER: You know, millions of Americans, just getting an ordinary job, would have to take one. It was constantly in the news and in politics because people who were mistrusted or somehow, you know, doubted would actually end up, you know, offering to take polygraph tests to prove their innocence.
KWONG: And Gina, this runaway implementation was happening without really any scientific evidence to back up the machine's accuracy, especially in real interrogation scenarios.
BARBER: Yeah, that doesn't surprise me, though, right? Because, I mean, throughout history, polygraph data has not been admissible in, like, most US courts.
KWONG: That is true, but there is a catch.
ALDER: While its results may be not admissible in court, if, in the process of lie detection exam, you confess the crime, that confession is admissible in court. And so the police use it to basically entrap people.
BARBER: That's awful. [LAUGHS]
KWONG: Yeah, the polygraph is not a lie detector. Experts have told me it's more like an anxiety detector.
BARBER: I would fail. [LAUGHS] Your anxiety would be palpable.
KWONG: Yeah. And ultimately, Ken told me, you know, the work falls on the examiner. There are professional polygraph communities with membership numbering in the hundreds. And they stand by the machine. But studies performed outside of the polygraph community have found high false positive rates. So the polygraph has many critics. Aldert Vrij, a professor of applied social psychology at the University of Portsmouth in England, is one of those critics.
ALDERT VRIJ: Because it's very naive to think that in interview settings, the truth tellers are completely calm because they're not. Very often, in these interview settings, if you're interviewed for a long time about a certain crime, the police believe you're guilty. But you're not. You're innocent.
BARBER: Yeah, I mean, like, regardless of whether you're guilty or you're innocent, I mean, just being around police could be nerve wracking.
KWONG: Right, so critics are rightfully cautious about these machines, even as pop culture makes light of them. Like, Vanity Fair is posting videos of celebrities getting polygraphs.
BARBER: Yeah, I mean, I've only seen the Pedro Pascal one, and I laughed my butt off.
KWONG: Yeah, the Keke Palmer one is pretty funny when she couldn't ID former Vice President Dick Cheney.
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KEKE PALMER: I hate to say it. I hope I don't sound ridiculous. I don't know who this man is. I mean, he could be walking down the street. I wouldn't know a thing. Sorry to this man.
SPEAKER 15: Is she telling the truth about that?
SPEAKER 16: That's true.
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BARBER: [LAUGHS] All right. But is the polygraph still being used for, like-- I don't know-- job screenings?
KWONG: In the security sector, yeah, for law enforcement officers.
BARBER: Wow.
KWONG: But the method has largely fallen out of favor. Since the late '80s, a federal law and many states have banned employers from requiring lie detector tests with very limited exceptions. But that hasn't stopped the deception field from trying to develop new methods. There are other lie detection technologies out there.
BARBER: OK, like, tell me the other kinds of ways we're trying to figure out if people are lying.
KWONG: Oh, it's every tech you can imagine. I mean, scientists have tried to measure lies with brainwaves, with fMRI machines, and with AI. And for a while, the deception field was captivated by the idea of micro-expressions--
BARBER: Right.
KWONG: --that a lying person could be caught by a skilled analyst of the human face.
BARBER: Yeah, I've heard of this, like, being able to tell if somebody's lying if they're, like, blinking too much, or they're not looking at you, or their face is twitching. As, like, a really anxious, like, kid and person, like, I read people's faces obsessively, like, trying to figure out if they're mad at me.
KWONG: And you probably have psychologist Paul Ekman to thank for that. I mean, he championed this idea for decades. But Regina, I am here to tell you that, like the polygraph, micro-expressions, everything you mentioned about, like, blinking, all that, it is also an unreliable form of lie detection.
VRIJ: That sounds like a good film script. And in fact, it is a film script because there is no research showing that really works in that way.
KWONG: Here's Aldred again, the psychologist at the University of Portsmouth who's been studying deception since the late '80s. And he, along with the majority of deception researchers, reject the micro-expressions model. And in a recent survey polling 50 researchers, a good number of them, like, over 80% of them, rejected another idea that a liar cannot look you in the eye.
TIMOTHY LUKE: The popular stereotype that a liar cannot look you in the eye, this is one of the few things that experts really agree just does not hold any water. We've got about a century's worth of data to demonstrate that this is the case.
KWONG: This is Timothy Luke, a psychologist at the University of Gothenburg in Sweden, and he was the lead author on that survey.
BARBER: And, like, this is-- you know, I know this goes against a lot of, like, what people think, but for me, it's not that surprising that, like, science doesn't really totally back, like, how to find a liar, right? Like, anxiety, gaze aversion, like, your face moving a little bit, none of these things are, like, universal. So is there any hope for Ari? Like, is there a step-by-step process for detecting a liar? Like, what do the experts say?
KWONG: So it's an important question to ask, and it really depends on who you ask. I can say that the field is changing and moving in a direction, away from nonverbal lie detection to verbal lie detection, so paying more close attention to what people are saying.
BARBER: Right.
KWONG: And then on the examiner's side, it's changing from, like, passive interviewing, where you're, like, in a monotone, like, "tell me everything you remember," to active interviewing, like, asking follow-up questions and analyzing specific details.
BARBER: Yeah, what details are they analyzing?
KWONG: It totally depends on the researcher. Aldert, in the UK, he believes that liars and truth tellers use different cognitive strategies. So he says that in, like, an extended conversation, liars will keep their stories simple, and truth tellers are more forthcoming.
VRIJ: Truth tellers are willing to tell it all, but initially, it doesn't really work that way, because truth tellers initially don't say that much. So what you need to do, you need to ask questions. And these questions, if you ask the good questions, what you will see, the truth tellers volunteer more information.
BARBER: Hmm.
KWONG: Now, Timothy Luke over in Sweden, he agrees that a lack of detail is a promising cue, but he actually questions the idea that there's any surefire cues--
BARBER: Right.
KWONG: --at all. It's been a conversation in the field pretty much since 2003. There was this big meta analysis led by Bella DePaulo at the University of Virginia. And Timothy has further argued in this paper called "Lessons from Pinocchio," that if there are cues, they may be overexaggerated.
LUKE: It's not going to be a very powerful indicator. It might be an indicator in a weak probabilistic sense. It might be detectable in a research context when you have recordings of people, and you're able to carefully observe and carefully document that.
KWONG: But the real world has so many variables. And Timothy thinks the very best liars can trick an interrogator. It also makes him really uncomfortable whenever law enforcement starts building policy around ideas that might not hold up to scientific scrutiny.
LUKE: If you have a policy where you are encouraging security officers or law enforcement to rely on potential cues to deception that might be weak, might be unreliable, and, also, might be highly subjective in their perception, that is going to open the door for potentially a lot of really problematic discretion. It opens the door for a lot of bias to creep into judgments. And that can be both completely innocent and by accident, as well as potentially more nefarious. So maybe we shouldn't be messing around with things that are this unreliable.
KWONG: Timothy thinks-- and there's a lot of disagreement in the field, but he says the best method for detecting a liar, like, the only technique he advocates law enforcement use, is called strategic use of evidence. It's an approach to interviewing.
LUKE: Where you, as an interviewer, ask questions in a way to get them to address the information that you have without revealing that you already have that information. That way, you have a kind of untainted statement to check against the facts that you have.
BARBER: Wait, so basically fact-checking.
KWONG: Yes.
BARBER: Fact-checking, I guess, is the best lie detector of them all.
KWONG: Yeah, what we do every Short Wave episode.
BARBER: OK.
KWONG: And Timothy Levine at the University of Alabama at Birmingham agrees that it is the only true way.
LEVINE: And anybody who's tried to fact-check knows it's really, really hard. And it's a real skill. But to the extent that you can triangulate with multiple sources and to the extent that the communication is about something factual, a good journalistic fact-checking will get you about as close as you can get.
KWONG: So that's the best we can do for Ari, is fact-checking.
BARBER: Emily Kwong, thank you so much for reporting. I now am validated that it was right that I trust no one.
KWONG: I wish there wasn't some truth to that, but maybe.
BARBER: [LAUGHS]
KWONG: This episode was produced by Hannah Chinn and edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts. Kwesi Lee was the audio engineer.
BARBER: Beth Donovan is our senior director, and Collin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber.
KWONG: And I'm Emily Kwong.
BARBER: Thank you for listening to Short Wave, the science podcast from NPR.
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