# Detecting lies, how hard can it be? **URL:** \ **Category:** Factual Questions\ **Created:** [November 8, 2011, 4:47pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287 "2011-11-08T16:47:16Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [November 8, 2011, 9:27pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/21 "2011-11-08T21:27:59Z")
> [@Danger\_Man](#): > > So what do these tests say? That they cannot detect lies at all? Or just a little bit better than random chance? The machines can be fooled at will by anyone who knows how they work or anyone who watched the Penn & Teller ep about them. > [@Laggard](#): > > Probably. I’m sure he can and has been lied to and fooled many times. My guess is that he is probably better at detecting it than your average person. Experts (judges, policemen, psychiatrists, etc.) identify lies 50% of the time under controlled circumstances. At least according to John Cleese in his documentary series called **Face.** It’s an odd cite, but it matches other things I’ve read that I don’t remember nearly as well. Oh, and all of the experts, when asked, claimed that they were good at spotting lies. **Face** reports that the 1% who identify lies exceptionally well are actually reading micro-expressions: facial expressions that last less than a second. Reading micro-expressions can be learned, but interpreting them can be tricky. The FBI does have a program for teaching the reading of micro-expressions. So if Laggard’s friend has taken the training, he may be more accurate than a tossed coin. If he’s saying he can “instantly tell” as if he can always tell, though, he probably hasn’t had the training. Or he thinks it’s good SOP to make the claim. The show **Lie to Me** is based on micro-expressions and other bits of research that show ways to catch lies that work better than 50% of the time. It has, of course, been Hollywooded beyond all recognition. Oddly, a recent study (don’t remember which science blog reported it) showed that people who watch **Lie to Me** are less able to detect lies than average. So watching the show will do you no good. Trust but verify. And don’t trust anyone waving lie detector results around. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [November 8, 2011, 9:40pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/22 "2011-11-08T21:40:05Z")
> [@notfrommensa](#): > > If someone is sure that they can tell someone is lying, he ought to make a good living playing poker. Not necessarily. He might be good at spotting other people’s bluffs, yet maybe his own bluffs are easy for other people to read. ---
**Author:** ![Gary\_Robson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gary_robson/32/3448_2.png) [@Gary\_Robson](https://boards.straightdope.com/u/Gary_Robson)\ **Post date:** [November 8, 2011, 9:42pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/23 "2011-11-08T21:42:41Z")
> [@Yllaria](#): > > Experts (judges, policemen, psychiatrists, etc.) identify lies 50% of the time under controlled circumstances. At least according to John Cleese in his documentary series called **Face.** This agrees with what Richard Wiseman said in the book _Quirkology_ that I referenced earlier. Experts are as good as flipping a coin. I find it interesting that Cleese talks about watching the facial movements to increase that percentage, but Wiseman did studies that showed people do better if they _can’t_ see the face. He did things like analyzing the number of words in the answer, counting the number of times people say “I” or “me,” and other lexical statistics. That improved the percentages to somewhere in the 70’s (I don’t remember the exact number), which is still a far cry from 100% – or even 90%. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [November 8, 2011, 10:42pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/24 "2011-11-08T22:42:32Z")
> [@Laggard](#): > > Probably. I’m sure he can and has been lied to and fooled many times. My guess is that he is probably better at detecting it than your average person. I doubt he can tell “instantly”. As has been mentioned studies have been done on this and the police are (IIRC) just a bit better than flipping a coin to determine if someone is lying. Good interrogation techniques however can get you good results. Ask the perp questions. Ask them again in a different way. Look for inconsistencies and exploit them. That is not a lesson on interrogation techniques but merely me saying that with some work an FBI agent very well may be able to reveal a liar with some regularity. I just doubt they can do it on the spot reliably. Indeed if he thinks he “knows” he can spot a liar “instantly” I would suggest this makes him a poor agent when questioning. His bias will assert itself and color his investigation from word-one. ---
**Author:** ![anson2995](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@anson2995](https://boards.straightdope.com/u/anson2995)\ **Post date:** [November 8, 2011, 11:06pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/25 "2011-11-08T23:06:27Z")
> [@Little\_Nemo](#): > > That’s my understanding. Lie detectors are not junk science - they are better than random at detecting lies. But they’re not good enough to be admissible in court. No, they’re completely junk science, little better than chance at detecting lies and what’s worse, have an alarmingly high rate of false positives. [The wikipedia page](http://en.wikipedia.org/wiki/Polygraph#Validity) cites about two dozen studies that have debunked polygraphs. Here’s a quote from one of the studies cited. > [@](#): > > Although the CQT [Control Question Test] may be useful as an investigative aid and tool to induce confessions, it does not pass muster as a scientifically credible test. CQT theory is based on naive, implausible assumptions indicating (a) that it is biased against innocent individuals and (b) that it can be beaten simply by artificially augmenting responses to control questions. Although it is not possible to adequately assess the error rate of the CQT, both of these conclusions are supported by published research findings in the best social science journals (Honts et al., 1994; Horvath, 1977; Kleinmuntz & Szucko, 1984; Patrick & Iacono, 1991). Although defense attorneys often attempt to have the results of friendly CQTs admitted as evidence in court, there is no evidence supporting their validity and ample reason to doubt it. Members of scientific organizations who have the requisite background to evaluate the CQT are overwhelmingly skeptical of the claims made by polygraph proponents. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [November 9, 2011, 12:01am UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/26 "2011-11-09T00:01:31Z")
[quote=“Gary “Wombat” Robson, post:23, topic:602287”] This agrees with what Richard Wiseman said in the book _Quirkology_ that I referenced earlier. . . . [/QUOTE] Sigh. I may as well put that on my Amazon wish list now. I’m going to end up buying it eventually. > [@](#): > > [from wiki quote above]. . . (b) that it can be beaten simply by artificially augmenting responses to control questions.. . . I think Pen & Teller recommended clenching your butt cheeks during the control questions or questions you were answering truthfully to and unclenching during your lies. Poetic, really. One of the episodes of **Lie to Me had** had a great visual for the prevalence of false positives. To discredit an ‘improved’ lie detector being touted to the FBI, the main character had an assistant with significant cleavage sit on the table near the machine and re-ask the questions while leaning towards the test subject. Suddenly the machine was marking every answer as a lie. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [November 9, 2011, 5:47am UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/27 "2011-11-09T05:47:00Z")
> [@anson2995](#): > > > [@](#): > > > > (b) that it can be beaten simply by artificially augmenting responses to control questions. I did this once. I was in high school and going for a job at the brand new, not opened yet, T.G.I. Fridays opening near my school (back then TGI Fridays was a fairly new chain…this wasn’t the first ever but they were a lot smaller than they are today…this is like 1983-84). I was going for a job as a bus boy and they were making every applicant submit to a polygraph (shit you not). Even at that age I knew how a polygraph worked so when the questioner asked me the beginning control questions I intentionally held my breath or clenched or paused. Apparently he could tell he was getting readings that would throw it off so he kept repeating the control questions (e.g. what is your name, how old are you, where do you live and so on). Eventually I stopped fucking around because I wanted the job. I just wanted to see if I could screw up the test and I could. It was trivially easy We then proceeded through all the questions and at the end I asked the interviewer about one question. He had asked, “Are there any hidden reasons you want this job?” I recall, when the question was asked, wondering what the hell that meant. So I thought about it trying to sort it in my head. Coming to no good conclusion I answered “no”. (FWIW he told me the question was to ask if I was a spy or somesuch to learn the secrets of TGIF.) When I asked him about that he smiled and said that was the only question I “failed”. I got the job (which was a good one for a high school kid…we got tip sharing from the waiters). Still, it taught me the polygraph was trivially easy to mess up. If a 16-17 year old kid can manage it who didn’t know shit from shineola I cannot imagine it is useful in the larger world. I suppose someone who is not the least bit knowledgeable about how the thing works and is honestly sitting there answering might produce better than coin-flipping results but a modicum of knowledge will ruin its reliability. They are not hard to beat. ---
**Author:** ![DocCathode](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/doccathode/32/18773_2.png) [@DocCathode](https://boards.straightdope.com/u/DocCathode)\ **Post date:** [November 9, 2011, 10:11pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/28 "2011-11-09T22:11:19Z")
I bring this up every time there’s a polygraph thread. I worked for years at a small company that sold medical sensors and software. I was often hooked up to a full range of sensors to show clients how to use the things. Polygraphs stink at detecting lies. Heartbeat, respiration, galvanic skin response etc can all be controlled with proper training. More than that, screwing up the readings is easy if you feel like it. The majority of the training was on how to get a nice and accurate reading free of artifacts. ---
**Author:** ![Precambrianmollusc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/precambrianmollusc/32/63_2.png) [@Precambrianmollusc](https://boards.straightdope.com/u/Precambrianmollusc)\ **Post date:** [November 9, 2011, 10:22pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/29 "2011-11-09T22:22:17Z")
Here is an interesting TED talk on the subject [http://www.ted.com/talks/pamela\_meyer\_how\_to\_spot\_a\_liar.html](http://www.ted.com/talks/pamela_meyer_how_to_spot_a_liar.html) I wonder if there is an XKCD on the subject as well. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [November 9, 2011, 11:34pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/30 "2011-11-09T23:34:47Z")
I think it was Oliver Sacks who wrote in one of his books about brain injuries about how aphasics (people who lose language) can tell if someone is lying, even though they can’t tell what the person is saying. He mentioned them finding political speeches on television to be hysterical. > [@Yllaria](#): > > Experts (judges, policemen, psychiatrists, etc.) identify lies 50% of the time under controlled circumstances. At least according to John Cleese in his documentary series called **Face.** It’s an odd cite, but it matches other things I’ve read that I don’t remember nearly as well. Oh, and all of the experts, when asked, claimed that they were good at spotting lies. I recall reading about a study some years ago where the ability of members of different branches of law enforcement were tested for their ability to detect lies. The only branch that was better than chance at detecting lies was the Secret Service; the speculation was offered that it might be because their job centers so much on watching people, observing them closely to see if they are a threat. ---
**Author:** ![Gary\_Robson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gary_robson/32/3448_2.png) [@Gary\_Robson](https://boards.straightdope.com/u/Gary_Robson)\ **Post date:** [November 9, 2011, 11:58pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/31 "2011-11-09T23:58:41Z")
> [@Precambrianmollusc](#): > > I wonder if there is an XKCD on the subject as well. There’s a [polygraph/seismograph](http://xkcd.com/711/) xkcd comic. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [November 10, 2011, 3:46am UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/32 "2011-11-10T03:46:53Z")
> [@Whack-a-Mole](#): > > I was going for a job as a bus boy and they were making every applicant submit to a polygraph (shit you not). My girlfriend back at that same time (1983) was applying for a job at Radio Shack. They (or at least, that store) made applicants take polygraph tests, too. (She apparently passed, as she got the job.) ---
**Author:** ![thirdname](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@thirdname](https://boards.straightdope.com/u/thirdname)\ **Post date:** [November 10, 2011, 3:53am UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/33 "2011-11-10T03:53:34Z")
If polygraphs are discredited, why does the government still require them for the highest security clearances? ---
**Author:** ![moejoe](https://avatars.discourse-cdn.com/v4/letter/m/9de053/32.png) [@moejoe](https://boards.straightdope.com/u/moejoe)\ **Post date:** [November 10, 2011, 4:08am UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/34 "2011-11-10T04:08:56Z")
> [@Danger\_Man](#): > > So what do these tests say? That they cannot detect lies at all? Or just a little bit better than random chance? I met a guy once who administered polygraph tests for a living. He said the key when you thought a person was lying was to convince him that the machine _proved_ he was lying, and then use that to get him to confess. Once you got him to confess you would have him write out and sign the confession and once you had that the polygraph didn’t matter anymore. He said it worked great for convincing people that they were bad liars. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [November 10, 2011, 8:39am UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/35 "2011-11-10T08:39:09Z")
Besides the problem of training to control responses; false positives because people are upset but not guilty (I often enough think “I know that I’m saying the truth, but will people who don’t know me believe me because it sounds unusual?” which stresses me and makes me blush); and people who don’t feel guilt for that particular thing (sociopaths; conscience clear for that question); there’s also the problem of memory. In a criminal or important session, the questions need to be not only “Did you kill Y?” but also “Did you do X?” “Where were you on …” But human memory is very suspectible to suggestion. (See several cracked articles). If either the suspect has himself convinced of an innocent version of events he can pass; or if the investigator asks questions that lead the suspect to remember a different, guilty, version of events he can fail. See the cracked article that confrontational normal interrogation gets about 1/3 false confessions (that is from innocents), but the soft approach (come on, just confess, you’ll feel better, we understand how you reacted) gets 2/3 false confessions! Adding lie detectors doesn’t help things. ---
**Author:** ![MLS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MLS](https://boards.straightdope.com/u/MLS)\ **Post date:** [November 10, 2011, 7:03pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/36 "2011-11-10T19:03:44Z")
Another anecdote about being able to control the output from machines – in this case not a lie detector but an ordinary BP/pulse monitor. My dad was in the hospital after some surgery or other, hooked up to one of these. The nurses had to keep going in to check on him because the machine seemed to show strange blips from time to time – sudden changes in pressure or heart rate. Finally someone noticed that the monitor was within dad’s view. He was \*doing it on purpose \*to see if he could make the lines change and by how much. The nurses moved the monitor. The strange blips went stopped. ---
**Author:** ![FlyByNight512](https://avatars.discourse-cdn.com/v4/letter/f/82dd89/32.png) [@FlyByNight512](https://boards.straightdope.com/u/FlyByNight512)\ **Post date:** [November 10, 2011, 8:09pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/37 "2011-11-10T20:09:57Z")
> [@thirdname](#): > > If polygraphs are discredited, why does the government still require them for the highest security clearances? That’s what I want to know. I’d like to do high-level security work at some point in my life, but I have an overactive conscience and could easily see myself getting a false positive on one of those things. Why in the world are they still using them? ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [November 10, 2011, 8:22pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/38 "2011-11-10T20:22:37Z")
> [@MLS](#): > > . He was \*doing it on purpose \*to see if he could make the lines change and by how much. The nurses moved the monitor. The strange blips went stopped. I did that once during a routine physical. The attending doctor was freaking out (and probably thinking about that new boat he wanted to buy). 🙂 ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [November 10, 2011, 9:49pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/39 "2011-11-10T21:49:37Z")
> [@FlyByNight512](#): > > That’s what I want to know. I’d like to do high-level security work at some point in my life, but I have an overactive conscience and could easily see myself getting a false positive on one of those things. Why in the world are they still using them? WAG: It’s easier to put the blame for a false decision in the hiring process onto a machine than having the guts to make the decision of yes/no by a person who then has to bear responsibility for a possibly bad decision? ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [November 10, 2011, 10:30pm UTC](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287/40 "2011-11-10T22:30:45Z")
The reason polygraphs don’t work is because polygraph machines have not changed since the 1950’s or even earlier. I submit the most recent episode of ‘Prime Suspect’ as evidence. I’m pretty sure that Thomas Edison built that machine. [Previous page](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287.md?page=1) [Next page](https://boards.straightdope.com/t/detecting-lies-how-hard-can-it-be/602287.md?page=3)