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The polygraph or lie detector test is frequently used in police investigations to determine, with a good degree of reliability, whether or not a person is lying when answering important investigative questions. It is a technique based on the unconscious physiological responses produced by lying. Most people cannot control these physiological responses.
However, there are people who have developed the ability to simulate physiological reactions that confuse the results and make them unreliable. In some cases, they can even fool the polygraph completely.
Passing a lie detector test is not the same as cheating on her
The polygraph is frequently used in legal contexts or during a criminal investigation. They can also be used during the job interview process to target high-level positions that have access to sensitive classified information. This goes to show that taking a polygraph test can be somewhat stressful, as the result has the potential to have major consequences for the test taker.
As a result, many people become nervous when answering questions, which may be interpreted by the evaluator as a sign of lying, when in fact the truth is being told. In other words, a person’s nerves may give way during a test. To prevent this from happening, there are different techniques that allow the interviewee to increase the probability of passing the test.
On the other hand, there are people who enter a lie detector test with the express intention of lying and getting away with it. For example, the ability to lie and cheat the lie detector test can be used by criminals to cover up their crimes and divert investigations against them.
However, there are situations in which it may be justified to want to deceive the polygraph. For example, in some cases, people use these techniques to avoid revealing personal or private information that is not relevant to the investigation. On the other hand, fooling the lie detector can mean the difference between life and death for an undercover agent if he happens to be questioned by the criminal organization he is investigating.
In the following sections we will explore how polygraphs or lie detectors work and some tips to fool them.
How does a polygraph or lie detector work?
As its name indicates, a lie detector or polygraph is a device that measures and graphs different physiological responses related to lying or telling the truth. The device consists of a four-channel meter that registers the following four variables in real time:
- respiratory rate
- heart pulse
- blood pressure
- sweating levels
Some more advanced polygraphs also monitor leg movement and other vital functions. These physiological variables are susceptible to mental state changes that occur when a person lies.
Regardless of the polygraph used, the lie detector test procedure follows a series of common steps:
The accuracy of lie detector tests
- The interviewer or evaluator connects the sensors and electrodes to the polygraph and places them on the interviewee.
- The interviewer asks the interviewee a set of simple questions such as name, age, nationality and others that make it possible to establish the baseline instrumental response. In other words, it sets the pulse, blood pressure, etc. corresponding to true answers.
- After establishing the base answer, the real interrogation begins, that is, the interviewer begins to ask the questions that really interest him. After receiving each answer, the interviewer observes the vital signs recorded on the polygraph looking for any abrupt changes that could indicate nervousness caused by lying. If when answering a question the changes in the vital signs are intense enough, it will mark the answer as a lie.
Depending on the degree of experience of the interviewer, it is estimated that these tests are reliable in approximately 87% of cases. However, it has also been shown that they can produce a relatively high number of false positives and negatives, that is, answers marked as a lie but are actually true, or questions marked as true that are actually a lie.
A typical example of a false positive that is relatively common is when a person is given a lie detector test and the person becomes very nervous just taking the test (and not because they plan to lie or because they have something to hide). When people get very nervous, they often generate physiological responses similar to those that occur when they lie:
- Their palms sweat.
- They start to hyperventilate.
- Increases heart rate, etc.
This can easily be misconstrued as a lie if the examiner is inexperienced.
On the other hand, there are people who develop the ability to mentally control their mood and nervousness, allowing them to remain calm and “poker face” as the interrogation progresses. By doing this, these people manage to disturb both the base signals during the first few questions, and the signals corresponding to the false answers, effectively confusing the examiner and leading him to mark the questions as true or, in the worst case, inconclusive.
The risk of convicting an innocent person for the mere fact of being nervous, as well as the risk of acquitting a guilty person capable of deceiving the polygraph and its operator, is the reason why the polygraph test is not taken into account in judicial cases.
But how exactly do some people manipulate the results to pass a lie detector test? Now that we have a good understanding of how the test works, we can discuss how to beat it.
Tips for Passing a Lie Detector Test
There are many sources of information that seek to teach how to cheat a polygraph. Although this may be justified under certain circumstances, it is not the intent of this article to give advice on how to lie and get away with it. Rather, this section is more about how to avoid having a polygraph test flag you as a liar when you are actually telling the truth, or leading you to confess something you don’t want or have to confess. With this in mind, below are tips on how to avoid false positives when taking a lie detector test.
Tip #1: Be honest
This is the golden rule for passing a lie detector test. If we do not want the polygraph to indicate that we are lying, we must start by always telling the truth. That said, it is possible that, despite the fact that we are telling the truth, our nerves betray us and we end up in a bad light.
Tip #2: Limit yourself to answering only what is asked
Many of the questions that the evaluator asks during a lie detector test can be answered simply with yes or no. If this is the case, we must limit ourselves to only one of the two answers. Indeed, we must at all times limit ourselves to responding in the most precise and concise way possible only to what is asked of us.
It should be noted that evaluators, especially the most experienced ones, are very astute when selecting questions, making sure to include both control questions and those relevant to the investigation, which are uncomfortable to answer or which may present an ambiguous answer. For example, we may be asked if we have ever stolen, and we may remember that once as children we took a toy from a classmate at school. In that case, we might be tempted to explain whether or not that would be considered stealing. These types of ambiguities can be dangerous because they make us nervous.
Tip #3: Choosing between constant nervousness or constant relaxation
Going back to the fact that the results of these tests are based on the variation of instrumental responses to true and false statements, the essential thing to pass a polygraph test is that we always remain in the same state of relaxation or agitation.
Very few people have the ability to remain totally relaxed and calm during a lie detector test, so many opt for the second option, that is, to remain in a constant state of tense nervousness throughout the entire interview. This manages to smooth out any abrupt changes in instrumental measures during the interrogation that could later be interpreted as a lie.
Tip #4: Learn to distinguish between control questions and relevant questions
As mentioned before, the interrogation includes a series of questions that serve to mark the baseline of the test. These control questions also serve to compare the behavior of the vital signs with that of the relevant questions. Learning to discern between a control question and a relevant one is very important because we want to make sure that we react in the same way in both cases.
Tip #5: Consciously Alter Your Mood During Control Questions
This is where following the advice above is justified. If we are aware of when we are being asked a control question, we can try to alter our vital signs as we answer them. Consciously altering the respiratory rate is very easy, but we can also control the rest with a little creativity.
For example, we can think of something that causes us anxiety such as a phobia or the risk that we will not pass the lie detector test. This will make the polygraph answer during the control questions more like the relevant answers that make us nervous.
Tip #6: Always respond firmly and with conviction
The firmness with which we answer a question can help us to be even more convinced of its truth, which in turn can help us control our nerves during the interrogation. In addition, a timid answer with little conviction will only pique the curiosity of the evaluator, who may decide to guide the questions to explore further, it can make us even more nervous.
Tip #7: The test does not necessarily end when the machine is unplugged
Once the interview is over and all the polygraph sensors are disconnected, we may be tempted to relax and let our guard down. Some evaluators take advantage of this situation to attack us with more questions or to make us nervous by telling us that they know we lied during the test. This may just be the tester fishing for an easy confession, so we must remain vigilant and on our guard at all times, even after the test is over.
References
Delgado, K. (2020, July 10). Why lie detector tests can be unreliable – and how to cheat them . Inews.Co.Uk. https://inews.co.uk/news/science/lie-detector-polygraph-tests-unreliable-how-cheat-388612
EcoDiario.es. (2018, November 23). How to pass the lie detector? elEconomista.es. https://ecodiario.eleconomista.es/noticias/noticias/9528987/11/18/Como-pasar-el-detector-de-mentiras.html
HowStuffWorks.com Contributors. (2021, April 15). How Does a Lie Detector (Polygraph) Work? HowStuffWorks. https://science.howstuffworks.com/question123.htm
infosalus. (2019, May 13). How can you fool the lie detector? infosalus.com. https://www.infosalus.com/salud-investigacion/noticia-puede-enganar-detector-mentiras-20190513103944.html
Wolchover, N. (2011, September 21). How to Pass a Lie Detector Test (Whether You’re Lying or Not) . Livescience. Com. https://www.livescience.com/33512-pass-lie-detector-polygraph.html
