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This podcast covers the fascinating world of psychological science through discussing the research behind popular myths related to psychology, such as the idea that we only use 10% of our brain. Hosted by Dr. Karla Lassonde and Dr. Emily Stark, psychology professors, we discuss misconceptions about psychology and how they have been researched by psychological scientists.
Karla, have you ever told a lie?
Karla:Well, I think so, right?
Emily:It's an interesting question to even try to understand. Research has tried to study how often we lie, but the way we study it is through asking people how often they lie. Sure. So we could lie. That tracks.
Emily:Yeah, yeah. When people do answer that question, it turns out that people tend to be honest. People report going dazed without telling lies. And that when they do, it's often what we call white lies, right? Like things like saying, Oh, I'm sorry, I was late for a meeting, when really I'm not sorry.
Emily:It's just, you know, social etiquette
Karla:Yeah, types of no one is harmed
Emily:in the telling of that lie. Right, exactly. Though there are some people who tell more lies and are dishonest. And if we think about the role of lie detection in solving crimes, we understand how it might be really interesting to figure out when people are lying and when they're telling the truth.
Karla:Yeah, we want that evidence, don't we?
Emily:Yeah. I mean, goes back. It was in the 1920s actually that a psychologist named William Moulton Marsden invented the first lie detection machine. And his machine measured blood pressure with the idea that liars might show a higher blood pressure. So we consider that like an early polygraph machine.
Emily:And that has been developed. What a polygraph measures today is more than just blood pressure. It also measures skin conductance and breathing rate. But it's the same idea that there's something physical about our body that could help signal when we are lying or when we're being dishonest. Just an interesting side note about William Moulton Marson, he was a person who did a ton of different things, including creating the character of Wonder Woman for comics.
Emily:Yeah. And remember she had her lasso of truth, right? So we can see that interest in lie detection maybe coming out in a lot of his different
Karla:It's either a really good coincidence or something that was planned. No, I like that. And so for the average person, there's this idea that your body is going to increase maybe your blood pressure, your heart rate, you might sweat a little more, and that these are some physiological markers that might be related to whether you're lying or not.
Emily:That is definitely the idea. There is just one problem with all of that, and it is that polygraph machines are not able to accurately detect when someone is lying. My name is Emily Stark and I'm a social psychologist.
Karla:And my name is Karla Lassonde and I'm a cognitive psychologist. And this is Brains Debunking Psychological Misconceptions.
Emily:Alright, let's get into this. Polygraphs or lie detection machines, they pop up a lot in media, both criminal investigations, but I don't know if you remember daytime TV programming, like maybe on the Maury Povich show where there'd be this gotcha moment, someone's gonna take a polygraph to figure out if they're lying. Right. But I think most people have a general sense of what they think a polygraph machine looks like.
Karla:Yeah. I think without getting into too many specific shows, you've got the SVU franchise. I think of Keith Morrison telling us that the The perpetrator yeah. The Dateline. Yeah.
Karla:I think that there's a a general interest and this general knowledge out there that, yeah, the polygraph is a thing, it's gonna happen, and it's part of that crime script, if you will.
Emily:Exactly. And some of how they're presented too suggests that they're infallible, right? That this is gonna be the way we figure out who is lying. If you've seen the movie, Meet the Parents, a very memorable scene has the gruff father-in-law Robert De Niro, he's polygraphing a very nervous Ben Stiller as part of Ben's first weekend with the family of his girlfriend. So he's meeting everyone and they get to this point of setting up a polygraph.
Emily:So I'm going to play just a short little snippet of this. You can hear them talk a little bit about the polygraph.
Meet the Parents Clip:Right. Looks complicated. Now these aren't a 100% accurate, right? They're
Meet the Parents Clip:Well, you'd be surprised how accurate they are. They can tell fairly if someone's lying enough. Now I'm gonna ask you some questions, and all you have to do is answer yes or no. Okay. All right.
Meet the Parents Clip:Let's give it a whirl. Did you fly on an airplane today? Yes, I did. No peeking. Did we eat pot roast for dinner tonight?
Meet the Parents Clip:Yes. Was it undercooked?
Meet the Parents Clip:No. It was rare. It was a little rare for my taste. But I I would kidding. I'm just
Meet the Parents Clip:Relax. Relax. The needles are jumping.
Emily:And so one thing you hear in that clip is the phrase, relax, the needles are jumping. Right? Which suggests that, oh, they can just look at what the machine is doing and it's immediately detecting if someone is lying.
Karla:Yeah. I mean, you go into that in a certain state. Right? So like Ben Stiller's really aggravated because he's super nervous. But yeah, like how do we interpret that?
Karla:Right away they start saying this is something.
Emily:Yeah, yep. Like, oh, look at this. This has to mean that you are lying. And a lot of people do see the polygraph as reliable or useful. A survey done, this was in 2006, so not super recent, but it found sixty seven percent of Americans viewed the polygraph as reliable.
Emily:And I mean, that's not the biggest number. So there's still a good number of people that maybe had some hesitancy. The majority of people still accepted that yes, a polygraph can detect lies.
Karla:Yeah, mean, we don't agree on a lot these days. So 67, I'll give it to you.
Emily:Right, not bad. That's a pretty strong number. I always ask my students about this when I teach my psychology and law course. And interestingly, at least this past semester, the majority of them viewed polygraphs as unreliable. And they also noted that polygraphs are not allowed in court, which is true to an extent.
Emily:Many states have fully banned the use of polygraph evidence. However, several states allow it under special circumstances. One example is that polygraphs are regularly used with sex offenders as a condition of their probation or parole, or can sometimes come up in courtroom trials if both the defense and prosecution agree to allow it to be entered as evidence. So you have this interesting mix of maybe some increasing understanding that, wait a second, maybe polygraphs aren't consistently included as evidence, but yet you also have people who think of them as reliable and they can be used sometimes. And one last place where polygraphing comes up that is not as represented in the media is in hiring.
Emily:That polygraphs are allowed to be used in hiring situations for jobs only with public employers. So the Federal Polygraph Protection Act, say that fast, that was back in 1988, and that banned private employers from using polygraphs and hiring, but public employers still can. The types of organizations that routinely use polygraphs include police departments, the FBI, CIA, other national security related organizations. And ever since nineeleven polygraph screening in hiring by these types of groups has only increased.
Karla:Yeah, we're a public institution.
Emily:Right, yes. I was just for disclosure, I was not polygraph when Correct. I was
Karla:was gonna say. Yeah. It's something that, you know, we always are grappling with tools. You can see it as like, why is there this in surge since nineeleven? There's this idea that this is somehow a tool, you know, a tool that can be used in decision making, right?
Karla:Like, is it the lie or is it something else that we think we're getting that's, you know, really relevant and useful data here?
Emily:Yes. So yeah, if we're using this as a tool, it's important to know, is this actually an accurate way to detect lies? And unfortunately, when research has tried to directly examine accuracy of polygraphs, it suggests we should be pretty skeptical of those results. Okay, so to talk about research into a polygraph, I first want to explain a little bit about how polygraphs work because one important thing to know is that there isn't actually a unique physiological response that occurs when we lie. So it's not as simple as just looking at like, oh, the needle has moved to this place and that for sure means you're lying.
Emily:So what polygraph examiners do, they are usually using a specific technique called the CQT, which stands for comparison question test. And so they start by asking a question that everyone is meant to lie to. An example might be, during the first twenty years of your life, did you ever take something that didn't belong to you? No. Most people have done this, but here's where it gets interesting.
Emily:If you say yes because you are being honest, you're prompted to say no. Or it'll be like, okay, other than that, did you ever take something that didn't belong to you? Like it's like they want you to lie in response to that question and the idea is like, now we have a sense of your physiological response to lying.
Karla:So there's a little bit of coaching there to get you to say
Emily:yes. Correct. A polygraph examiner is, they want to get you to the lie. So they're trained in how to respond. So if you're answering honestly, they're going to keep working, like trying to get you to a point of saying, Okay, but now say no, like this.
Emily:But it's not quite that overt, right? They can't just tell you, you have to the idea is you have to feel like you're lying. Okay. And if this already sounds a little difficult and confusing. So this is the whole base of this approach.
Emily:And it's hard to know how any one individual, even if they immediately lied to that, are they particularly upset about admitting to shoplifting or whatever they're referring to? It's hard to know what that means when we're measuring their response to lying to that comparison question.
Karla:Yeah, I mean, think of human beings. If you think of the different children that you know, how they may look, feel, think different, when they're confessing or not, and even the range of emotional reactions that the average person has or doesn't have, it's wildly different.
Emily:Right, yes. There's so much variation. And so just interpreting these is difficult. And like we'll get into, that is part of what makes it not reliable. So first we get this picture of what it looks like when you are lying.
Emily:And then the polygraph examiner is moving on to ask some questions that are unrelated to the crime, or if this is a hiring scenario, sometimes they're asking hypotheticals or things like, have you ever, I don't know, stolen things from a previous job? And then they ask questions that are related. And so what they're looking at is when they're asking you questions about a crime, and do those physiological responses look like the response that you made to that first comparison? Sometimes that's called a known lie question. And then that's what we're comparing to figure out, wait, are you does it look like you're also lying about this crime?
Karla:Okay. When you think of that comparison then, Emily, you want it to be more exaggerated than the lie that they kind of coerced you to say, Now you're in the scenario of the crime or the event that's taking place, And so you're looking for a heightened response or, I don't want to say larger, but more of a physiological indicator.
Emily:Exactly right. So that is the idea. If you committed the crime and are lying about it, we should see an exaggerated physiological response compared to that known lie question. And if you didn't commit the crime, so you're telling the truth about not doing that, then your physiological response should be less than that known lie question. That is the underlying so called logic of the polygraph.
Emily:There are a lot of potential issues with that. One is that there aren't validated specific questions that are used as known lie questions, or even one specific procedure that goes through the different types of questions. Each polygraph examiner has their own specific way of running a session, which makes just testing for validity and accuracy even more difficult. And some polygraph examiners will even say like, Oh, this is more of an art than a science, which is always something that I am suspicious of and hate to hear when we are trying to generalize and learn things about people. Yeah.
Emily:That was not an art. You have to know what you're doing.
Karla:Well, an art is to say lying yes or no, it's a dichotomous choice. It's either on or off, yes or no. That is a far cry from this idea of the subjectivity of an art.
Emily:Yes, yeah, right? We're trying to detect a thing about someone. We should be able to have specific procedures if we can do this in a consistent and accurate way. So that is the first issue. And then also connected to that, it is the polygraph examiner that's making those comparisons and they're the ones deciding if a response looks truthful or is lying.
Emily:Sometimes in the media it makes it suggest like, Oh, the machine is saying if you are being dishonest, but it's really not. These are human judgments. And again, even within that, different examiners have different approaches to scoring. Like how much greater does the amplitude of response need to be to indicate a lie? There is no standard assumption or process for that.
Karla:Yeah. I mean, in psychological science, we look at the reliability of a response. And so if you have all these individuals and they are uniquely changed in a somewhat subjective way, it would be really hard to say, Is your interpretation of the lie detector going to be the same as mine? It sounds like the way they've set up the course of the lie detection process is that, Oh no, it can be different because of my artful interpretation over yours. It doesn't smell like the rest of psychological science.
Emily:Yes, yes. This is not how science approaches making these types of judgments. And just one last problem that is relevant to bring up. Imagine that you are being questioned by police about a possible crime, you're probably going to be anxious. Maybe especially if you're innocent.
Emily:So even if you might be telling the truth to saying that, No, I did not do this, you could imagine having a heightened physiological response. And so particularly for innocent people, this this like fear of questioning or uncertainty about what is happening could also be affecting how they're responding to the polygraph measures.
Karla:Yeah, undoubtedly. There's the individual difference part too.
Emily:Yes. So research studies have tried to directly study the effectiveness of the polygraph. However, many studies that have tested polygraph accuracy, they use what are called mock crimes. So people are lying about pretend crimes for the sake of a lab experiment. And you could certainly argue that this isn't really replicating the real life stakes where a polygraph could be used.
Emily:However, researchers have been able to pull from, say, actual video tapes of interrogations and polygraph use where we can be pretty sure when people were lying and when they were telling the truth. But again, with that it's hard to be completely sure, right, if they, when they were lying not. And so the research is, it's difficult to really do research that replicates the types of situations where polygraphs are actually used. Now that said, a committee of the National Research Council, and this is part of our National Academies of Sciences, it's designed to bring experts together to both conduct and evaluate research to provide broad recommendations. This was convened to review just all the different studies on the accuracy of the polygraph.
Karla:Oh wow!
Emily:Yeah, so they looked at all of this research and they issued a report in 2003 with their findings and recommendations. And this involved a lot of prominent psychologists, many of the people who had participated in designing some of this research. And really what their report said was they found few studies that were high quality and that could actually seem to be replicating like an intense situation, but where we knew if the person was lying and telling the truth.
Karla:That's interesting from your discussion of the report, it sounds like it's one of the most densely, like where they went and pursued real information, had real people that do this, and they found very little evidence of something. Yeah,
Emily:right, yeah. They also, one of the things that they were able to pull out so imagine if you had 10 people that you were all interrogating and one of them committed the crime and everyone said that they didn't commit the crime and the polygraph said everyone was lying. So it's going to get the person who committed the crime, but it's going to be wrong the other nine times. And so that piece also complicates this type of research. I'm not going to get into the details of signal detection theory, but it's really saying that the polygraph, it doesn't only need to identify the liars.
Emily:It also correctly needs to identify the truth tellers. Sure. It cannot be saying that truth tellers are also lying. And that was another conclusion of this National Research Council was that polygraphs do tend to find, I'm making quote marks around a the word lot of deception. Deception.
Emily:So it does seem like if you are innocent or if you are telling the truth, you are perhaps more likely to be judged as deceptive from a polygraph.
Karla:Yeah. So it's not a baseline of fifty fifty, where you're going into this and it's authentically, Hey, we don't know what's going to happen. It sounds like there's a lean or a bend toward finding lying.
Emily:Yes, exactly. That does seem to be what comes out of some of this. So the overall report said that the current research suggests that polygraph testing can possibly discriminate liars from tooth tellers at rates that are slightly above chance. So there's something there, like this is not completely flawed. But the accuracy is too low for these approaches to be used in job screening or crime investigation, especially due to the risk of implicating innocent people.
Emily:And they basically recommended that more research is done, both to help improve polygraphing and they suggested maybe other research that, there could be other potential ways to detect lies. So maybe using fMRI or other types of brain measurement, right, we could improve our ability to do this.
Karla:Yeah, I mean you don't want to throw it out completely because what they are doing, folks that might be trained in the polygraph, they are trying to study human behavior. They are trying to use their best knowledge. They're not going at it, I think, in a vindictive way. Like, this is not I'm trying to cause harm. But, you know, we kind of say maybe they are causing harm if we're finding a higher rate of liars, but to the point they're attempting to do something right.
Karla:One would hope so.
Emily:However, there are some concerns. So this report wasn't binding, meaning that it didn't require anyone to change what they were doing. It was just a recommendation. And yes, you would think then that people who do use the polygraph would take that report seriously and perhaps try to change their procedures, but that is not what happened. When we look at studies conducted by industry groups such as the American Polygraph Association, they claim to find higher rates of accuracy.
Emily:So the people conducting the polygraph don't agree that there is a problem with the polygraph, and are perhaps not motivated to do more research or consider these potential flaws when they do this. Polygraph examiners show a lot of confidence in their findings. I could say like, I am always correct, which is
Karla:never true. This reminds me, Emily, of like the sugar industry and without getting into maybe what could be another episode, but the sugar industry doing some of their own research by their own research lab showing that sugar isn't really a problem health wise.
Emily:Yes, right. Are we thinking of like the tobacco Yeah, old companies tobacco. Same types of things. Yes. And again, if we, you know, to give the best possible life, imagine you're a polygraph examiner that works with the police, You might never learn about the outcome of a case, right?
Emily:Like you might not be getting feedback on the work that you're doing. So if you are not testing yourself, then you're going, you might think that your process is completely accurate.
Karla:Of course.
Emily:So without that regular feedback, yes, you could have an inflated perception of accuracy. And this also relates to confirmation bias. If you think that someone is guilty and your polygraph said they were guilty, look at that in your brain everything You is did it correct. And so this is a place where that type of bias, it could lead the people using polygraphs to be overconfident in the reliability of those outcomes. Just one final point to make an interesting study that I found when I was looking into this this was just published in 2025 it found that people who refuse to take a polygraph exam are often viewed as guilty, Even when participants agree that polygraphs aren't perfect, this idea that, oh well, refusing a polygraph makes you look guilty.
Emily:And that, let's say you're being investigated for a crime, you refuse to take a polygraph, this could be leaked in the media, a witness in court could let this slip, and this could influence a jury.
Karla:Yeah, it's like lying through omission.
Emily:Yeah.
Karla:By not doing something that you're inherently guilty, which is too bad, right? Because if someone comes in, or not, and they've done their research on the polygraph test, they're like, well I'm not going to take it because I listen to the show or whatever. Yeah, it's like if you have this sense, not that that's the case for the individual, but you're being punished twice.
Emily:Absolutely. I mean, at minimum information about whether or not someone took a polygraph should never be mentioned in courtroom trials. But again, we need to address the accuracy of the polygraph. If it could be a more accurate tool, then a lot of these problems go away. But currently, we cannot be sure in the outcomes of a polygraph.
Karla:Alright Emily, well what is the key takeaway here?
Emily:Well, Carla, overall scientists agree that polygraphs are not valid or reliable enough to be used. And another piece, mistaken results from a polygraph could lead to people confessing to crimes they didn't commit or people not getting jobs they are perfectly qualified for. There are some pretty major concerns with the use of polygraphs. This also highlights the need for continued research into a lot of different crime investigation techniques like the polygraph to ensure we're not making mistakes when we investigate crimes. And like I mentioned before, there's some exciting new work being done that uses brain imaging techniques like fMRI.
Emily:These approaches need more testing and refining, but they could also, there's potential to identify liars. Like when are you remembering something that's actual versus making something up completely? That is, there's promise there. Good news. Yes.
Emily:Until then though, we should be suspicious of polygraph tests and ideally perhaps work to decrease how often they are used. Until we can develop a more consistent and reliable approach, we should not be continually using this tool that has the potential to harm people while not providing us with useful information.
Karla:Yeah, think that's a tremendous takeaway.
Emily:You heard it here on Brains versus Beliefs. You can learn more about this podcast on our website called communicatingpsychologicalscience.com. You'll find references and a link to the episode. Feel free to contact us on our website with any comments or ideas for future episodes and follow Brains versus Beliefs wherever you find podcasts. Thanks for listening.