When was the last time you lied? Even if you consider yourself honest, you’ve probably told a fib from time to time. Sure, it’s not like you’re telling egregious lies that could harm people, but the reality is we all lie when we need to.

A study by psychologist Robert Feldman from the University of Massachusetts in 2022 shows 60% of people lie at least once during a 10-minute conversation, and most people average two to three lies. Why do we lie? It’s understandable why we would do it to protect ourselves in a situation that could cause us harm, but we do it all the time for all types of reasons.

When most of us lie, we feel terrible about it. It plays on our conscience if it’s a serious lie, and we feel guilty about our transgression. Some people don’t have this problem. Sociopaths, psychopaths, and pathological liars are comfortable lying all the time. So, what’s the difference in psyches between these individuals and normal people?

The primary difference is how we respond to telling lies. Besides the guilt lying causes to the average person, it also creates a physiological response when we tell fibs. This post unpacks why we lie and the reaction it creates in our bodies when we do.

Why Do People Lie? What are the Reasons for Lying?

There are several reasons why we decide to tell lies. It’s impossible to list all of them because the reasons vary widely, depending on the individual and the situation. We curated this list of the primary motivators for telling lies. It applies to adults, children, men, and women.


Avoiding Reprimand

People will tell lies to avoid being reprimanded by others. Another notable example is the teen caught sneaking into the house after their curfew. They claim they lost track of time and had no idea they were late. In reality, they know exactly how late it is and that they would be in trouble if they got caught.

Avoiding punishment is one of the top reasons why people tell lies. For instance, you arrive late to work because you didn’t get out of bed in time, and you tell your boss you found your car with a flat tire when you got to the driveway to go to work.

With serious lies, there’s a threat of punishment, causing you to commit the transgression. The teenager is trying to avoid a grounding, and the employee is trying to avoid a warning. It’s usually in serious lies where people give away their guilt with their body languages, such as a drop in their voice or a change in the micro-expressions on their faces. Typically, they’re unaware of these changes.

The threat of punishment creates an emotional overload, creating involuntary changes in behavior that a trained eye can identify. When told flawlessly, everyday white lies are challenging to detect.


Concealing Benefit or Reward

In most instances of telling serious lies, the person does so to conceal a benefit or reward from breaking expectations or rules. For example, a traffic officer pulls you over in the morning for speeding on the way to work. You tell him your phone went dead and your alarm didn’t go off, and that’s why you’re in a rush. In the meantime, you were speeding because that is how you like to drive most of the time.

Or you could tell your wide you were working late at the office when you were really at the motel with your side-piece. In both examples, you don’t pay any price for your actions if the other person decides to believe your lie. The subjects of these examples also determine the cost vs. reward when telling a lie well before making it. It’s an intentional deception designed to conceal their behavior.



People will lie to protect themselves from harm. For instance, the schoolboy plays a prank on someone, and when questioned about their involvement in it, they try to pin it on someone else to avoid the bully beating them.

Or there could be a child home alone at the house. A stranger arrives at the door, asking them if they can come inside to check the electrical meter. The kid, suspicious of the stranger, tells them to wait outside while they go upstairs to get their father, who’s taking a nap. They close the door, lock it, and call the police.

We also tell lies to win approval from other people. If you decide to boast about things you never achieved, like making money off Bitcoin when, in reality, you lost, it would be a good example of lying to preserve your reputation and prevent you from looking foolish to your peers.

There’s also the occurrence where you tell more serious lies to cover severe problems and offenses. For instance, the trader lies about their losses to their investors to avoid drawdowns on his hedge fund. He knowingly commits financial fraud because he’s confident he can make money back for his clients.


Protecting Others from Harm

People may also tell lies for more noble reasons, like protecting other people they care about from harm. For instance, your boss tells a colleague they were late to work, they deny it saying they were on time, and you back them up because you don’t want to see them get reprimanded by the boss.

It’s not certain whether these types of lies are noble and acceptable to make. Society is sort of on the fence about the severity of these fibs. These lies may cover up something innocent, like your brother getting home past his curfew and you backing him up with the parents saying he got home on time.

Or they could be as severe as police officers covering up evidence of the use of excessive force in an arrest. In this case, the act of lying to cover up other people’s offenses is seen as heroic, and you can trust the other person not to “rat” on you.


Privacy Issues

People will lie to maintain their privacy. For instance, a girl challenges her friend because she thinks she is speaking to her boyfriend on the phone and suspects him of cheating on her. Her girlfriend replies, saying she was talking to someone else, and her friend should chill out, despite being on the phone with her boyfriend.


To Avoiding Being Embarrassed

People will lie to avoid embarrassment. They may lie to cover up serious shame or minor infractions. For instance, your friend asks what you watched on TV last night. You tell him you were watching Rick & Morty, so you appear normal when in reality, you were watching Gilmore Girls. Or you could claim you’re a vegan to your friends to look cool, despite enjoying a trip to Mcdonald’s for a Quarter Pounder with Cheese twice a week.


Out of Politeness

Some people may deceive others out of being polite. For instance, your girlfriend asks you if you like her dress, and you tell her it looks good on her, despite thinking it’s atrocious. These are minor “white” lies similar to bluffing about your cards in poker.


For the Thrill

Some people will lie just for the entertainment factor and psychological thrill of doing so. Many kids will lie to their parents to see if they can get away with it. They get a kick out of purposefully manipulating people. It’s somewhat sociopathic behavior, and people using this strategy are at risk of becoming pathological liars.


How Lying Makes Changes in the Brain


Friedrich Nietzsche believed lying is a part of life and a common and recurring phenomenon in people. Considering this statement, the psychological impact of lying, and its effect on us when we’re on the receiving end, we don’t like dishonest behavior in others, despite its normalization and frequency in society and relationships.

Most honest people don’t enjoy lying. If they find themselves doing it out of necessity, they’ll usually feel guilty, which weighs on their conscience. Lying generates mental stress, internal discomfort, and dissonance.

Fortunately, science has more of a grasp on the physical impact of telling lies than in the days of Friedrich Nietzsche. A study published in Scientific American shows that people get more accustomed to the internal struggle they feel telling lies as they tell more lies in life. The plasticity of the brain and its neural networks allows it to adapt to our behavior, including dishonesty.

Nature Neuroscience reported on a study on the part of the brain responsible for dealing with emotional responses, known as the amygdala. As we lie more frequently, the reaction in the amygdala shows up less. We can conclude from this that our guilty feelings weaken the more we lie.

This process accelerates if we tell a lie and get away with it. Other research also indicates most people don’t like thinking of themselves as liars. As a result, we’re likely to try and justify to ourselves, or others, our reasons for lying and that we did so with good intentions.

When we lie, the brain creates feelings of overwhelm. Research on the health effects of pathological lying shows it may be detrimental to physical and mental health. Arthur Markman, Ph.D., has research showing that our adrenal system manufactures the hormone cortisol the moment a lie leaves our lips.

As a result, a few seconds later, your brain goes into overdrive as it tries to remember the lie and decern it from the truth. It’s like trying to study for a test. As a result of these mental processes, our decision-making process becomes challenging, and we may even project feeling as discomfort as anger.


Physiological Changes with Lying – Understanding the Stress Response

After we experience the initial mental reactions in the brain from telling a lie, we start worrying about being caught out. To compensate for this feeling, we’ll attempt to make up for it but treating the other person with greater kindness or compassion than normal.

Or we take the opposite approach and get angry with them as we convince ourselves that we had to lie in that situation because it was the only choice. Around 48 hours after telling a lie, we might feel guilty about our lying behavior and avoid running into the person we lied to.

If you continue to feel guilty about the lie, you’ll experience disruptions to your sleeping pattern. This stress has adverse effects on your health. The feelings of guilt left unchecked can increase blood pressure, headaches, lower back pain, and reduced white blood cell count.

A significant amount of mental energy goes into sustaining a lie. Some people who feel really guilty about the transgression may develop anxiety from it or fall into depression. The effects extend into creating poor digestion, producing symptoms of cramping, nausea, diarrhea, and vomiting.

Researchers at Notre Dame looked into the physiological effects of lying pathologically. The tests involved 110 volunteers, with half told to refrain from lying and the other half receiving no instructions. By the end of 10 weeks, the group that told fewer lies said their mental health improved by over 50% on average.


The Impact of Stress on the Body and Behavior

Some people feel uncomfortable about being forced into a situation where they must lie. Initially, this might seem inconceivable to many, but it occurs more frequently than you imagine. For instance, people might decide to lie if they cheat on their partner or hide parts of their past from other people.

Lying is also common in school and work environments where kids experiencing bullying may refuse to speak about it at home, insisting that everything is okay at school. Or people might say they love their work when they dread getting out of bed in the morning at the thought of going into the office.

If they keep this behavior up[ for short periods, they typically won’t experience any mental distress. However, if they have to keep up the charade for weeks or months, they’ll likely start to experience the symptoms of psychological and physical stress on the mind and body.

The brain interprets this stress as an attack on the body, creating internal contradictions and mental tension. As a result, the brain signals the body to create the stress response, resulting in the problems we discussed earlier, like insomnia, muscle discomfort, and digestive issues.


How Does a Polygraph Initiate the Stress Response?

People who undergo a polygraph test typically find the experience rather harrowing and stressful. Even if they haven’t done anything wrong, their mind races, considering every digression they’ve ever made. These felling bubble to the surface of the mind, creating the stress response known as the “fight-or-flight” mode.

Fight-or-flight is a response to the sympathetic nervous system signaling the adrenal glands to flood the body with the hormone cortisol. Initially, our ancestors evolved this response to help them in a primal state when predators chased them. There is no such threat today, but we’ll experience it through other means.

For instance, you’ve heard the story about a mother lifting a car to rescue her baby or people jumping out of three-story windows and surviving in the event of a fire. Or maybe you wake up late one night to hear someone attempting to break into your house, and your senses heighten, your heart starts beating fast, and you start shaking in fear.

These are all examples of the fight-or-flight response in action. When cortisol gets going, it’s impossible to stop these physical reactions from occurring. So, when you’re strapped up and sitting in a chair taking a polygraph test, your mind is already entering fight-or-flight mode. It’s a stressful situation because you don’t know what to expect.

The fear of the unknown gets the cortisol flowing, and all it takes is the examiner to ask a question where you have to lie, and you’ll feel a shock run through your body and mind. Your blood pressure rises, your pulse rate and respiration increase, and your skin start to sweat.

While the polygraph examiner can’t pick up your mental state, they can easily identify these changes in your physiology. The sensitive apparatus they use and the software program that interprets the signals from this equipment can tell if you’re being “deceptive.”


Wrapping Up – Can You Control the Stress Response and Beat the Polygraph?

The power of the sympathetic nervous system, the fight-or-flight response, and cortisol flooding your bloodstream is a hard combination of factors to control. Many assume they can control their emotions and lie their way through a polygraph with no issues.

However, it’s a very different story when they find themselves in the chair in the examination room. It requires tremendous willpower and mental discipline to control this response in a stressful situation, and most people can’t pull it off.

The examiner also records the entire session, and they’ll review the footage later after completing the test. They’ll look at your physical response when answering the questions. The examiner has extensive training and experience in identifying body language, and they can identify the changes in your body and face when you lie.

They compare this footage to the data recorded by the software and use it to determine if you’re being deceptive or telling the truth. While some people may find they can beat the machine, they’ll have a tough time undermining a trained professional with thousands of hours of experience assessing deception.

That said, polygraphs are not infallible, and there are plenty of stories of people beating them. However, you’ll need complete control over your emotions. Most people will crumble under the stress response and fail the test if their guilty and lying.


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