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Human Lie Detector

Knowing how different emotions manifest physically is both interesting and useful. But let’s face it; what we want the most is to know when we are being lied to, and we can get closer to that goal by putting these skills into practice. Realistically, it would take years of practice and practical application to be completely accurate, but in most situations outside of law enforcement, any improvement made in these skills will help.

1. How to Spot a Liar

Within a ten-minute conversation, a person could tell up to three harmless “white” lies. Many of us tell as many as two hundred lies in one day. Strangely enough, the lying statistics seem to go up during the Christmas season, possibly out of good intentions. Christmas is a time most people want to feel good; the increase in lying could arise from a desire to make people feel better or spare them from bad feelings.

The first step to being a human lie detector is to know how a liar operates. Without a polygraph machine to detect blood pressure, other techniques must be used. Body language is, of course, one of the best ways to spot a liar without using a machine. But there have been studies that show some other ways to detect when someone is lying. Possibly some of the most reliable ways to accomplish this are to determine how well the person can manage detailed information and to determine if they seem to be overthinking. Overthinking has been found to be a very good indicator of a dishonest person.

Liars tend to have better verbal functioning or working memory. Your working memory is what holds both previously stored and new information. A liar uses this memory to facilitate various pieces of information as they attempt to remain aware of what the person being lied to already knows. In one study, some children were left in a room to play a trivia game. The final answers to the questions were printed on the backs of the cards. What they didn’t know is that their actions (whether they cheated or not) were being recorded. The ones with a lower capacity for verbal working memory gave correct answers to the questions meant to entrap them. They had cheated, of course, but had been unable to recognize that the nature of the questioning was leading them into an unwitting confession. The children with more proficient verbal working memory were sneakier and could more easily avoid the traps.

Overthinking is another good indication that a person is lying. In another study participants were told to listen to someone tell a story of a vacation experience. Of the participants were able to ascertain that some people seemed to be thinking too hard about their stories, therefore indicating dishonesty.

Lying will cause significant stress in most people. Some people’s noses will change color (either very red or pale) when they lie. This reaction has often been called the “Pinocchio Effect.” Coughing is also a red flag. If someone starts coughing suddenly during a conversation, they could be lying.

On occasion, a person’s voice will change pitch. The stress causes their voices to increase in pitch and get higher when they fib.

Stuttering and language changes can reveal a liar. If they suddenly have a hard time getting words out (as when stuttering), they hesitate too much, or start using stronger language, chances are they are lying.

2. How to Detect a Lie

Now that we know how to spot a liar, the next step is learning the correct process for beginning to investigate deeper. Noticing the outward signs of a liar won’t get you the answers you need, but neither will an open confrontation. One of the downsides of detecting lies without the help of law enforcement and their modern technology is you have to be patient. Get to know the person better, establish a baseline for social norms, learn what the right questions are and when to ask them.

Determine pacifiers

Obviously, a big part of knowing when someone is lying is to be able to recognize when they are uneasy. Honest people are calm and collected while liars are understandably stressed out. When we are stressed or upset, we sometimes develop ways to pacify ourselves. Some pacifiers could include stroking the hair, fiddling with jewelry or a piece of clothing, placing the hands over the eyes, even rubbing the neck or pursing the lips. Getting to know a person’s specific pacifiers will help you determine how comfortable or uncomfortable they are around certain situations or topics. If you know someone hates sharks and he rubs his palm on his pants every time the topic comes up it is reasonable to assume that gesture is a pacifier for him and not an indication of lying.

Establish physical and auditory baselines


The physical baseline involves a general knowledge of body language and facial cues. Baselines are a part of the lie detecting process in law enforcement when a polygraph is used, and it is still an important step even without it. As we have learned, one of the signs of unease is rubbing the back of the head. You already know that a person rubs his neck to calm himself down and having that knowledge before questioning someone could save time when trying to find the truth. If you know how they typically respond to certain stressors or questions, it will make any deviation from the norm that much more noticeable. Granted, of course, that you already know or have observed a person for some time. So how does that help with new acquaintances? The answer is to pay attention. People are usually naturally shy or nervous when meeting someone for the first time. Pay attention to their reactions when meeting them for the first time and observe them throughout the course of the conversation. It is important to remember that not all signs of unease or nervousness indicate a person is lying. It will require further investigation before coming to a hard conclusion.

The auditory baseline entails paying attention to things like what their normal speaking patterns are and the types of words they use in a relaxed environment as opposed to a stressful environment. Take note of things like speech patterns, natural and unnatural voice inflection, and even how often they use filler words such as “ah” and “um.”

Utilize a relaxed environment

If you have accurately determined an individual’s pacifying rituals, make sure they are comfortable speaking with you before asking potentially incriminating questions. You want to know that they are comfortable so you can notice the changes in their behavior. A comfortable person will tend to lean in during the conversation, their arms will not be crossed, and they will have a generally relaxed air about them. If the pacifiers emerge, there is a good chance that, for whatever reason, they are very uncomfortable with the conversation and they could be lying.

Questioning Tips

It’s not always enough to know the visible signs of a lie. It is important to know what questions to ask and how to ask them. Ask non-judgmental questions. If someone feels like they are being accused or attacked, they will most likely get defensive, even if they are not guilty. Be calm and detached and give no indication that you suspect them specifically of anything. Be specific. Make sure the questions are appropriate to the context of the situation and are not vague. Be aware of red flags at any point during the conversation. Some of these red flags are changes in body language, voice inflection, etc. If the red flags are present, they are either just really uneasy with what you are talking about, or they are lying.

The logical next step is to dig deeper. However, take the time to consider carefully if the situation is important enough to lead to the inevitable drama that arises from catching someone in a lie. This is the turning point of the conversation: They show signs of discomfort and, if they are actually lying, they will probably have figured out where the questions are leading. If you decide to stay on that course, then start changing your style of questioning. Ask open-ended questions to force the person to give more details and speak longer. This will then give you more observation time. Then go ahead and dig deeper if you are still unsure. If the story has a timeline, does not give them the opportunity to start at the beginning. Falsehoods are often memorized in chronological order. Remove that, and it will be much more difficult for them to stay consistent.

If you really need to, try asking a completely unexpected question. Their trail of thought will be completely thrown off, and they will probably forget key pieces to their practiced false story. If this happens, there is actually a good chance that pieces of the truth will slip in to fill the gaps they are missing in their lives.

Additional signs of deception

Another helpful sign to look out for is consistency with the verbal and non-verbal events of the situation. If a child has been kidnapped his mother would be quite distraught and hound the police to find the child. Any reaction less than hysterical, such as detachment or coldness would lead one to believe that there is something suspicious going on.

Consistency in head movement is also something to watch out for when questioning someone. If a person nods or shakes his head while speaking, he is probably telling the truth. If the head movement occurs after he answers the question, it is most likely a lie. A liar will sometimes say yes while unconsciously shaking his head, which is an obvious sign of a lie.

The lack of movement could also be a useful indicator. It is very unusual for a person to be motionless for an extended amount of time. However, instinctive behavior of humans and animals alike is to become motionless during times of distress. Liars will purposely keep their bodies motionless to avoid getting caught or being found out.

Lack of articulation when speaking could mean someone is lying. When our brains don’t have to focus so rigidly on what we are saying our subconscious throws in gestures and inflections in our words to help get the point across. When we have to think too hard about what we are saying, most of those gestures will diminish or disappear entirely.

Fun Facts

Different cultures have their own methods of detecting lies which they have used for centuries. If someone was suspected of a crime in ancient China, they would put dry rice in his mouth during the questioning process. If the rice was still relatively dry when the questioning was over, he was considered guilty based on the theory that a side effect of nervousness is a dry mouth.

In Africa, the presumed guilty party would be questioned while holding an egg between his hands. If the egg broke at any point during interrogation, it was seen as evidence of tension, and he would be proclaimed guilty.