Polygraph tests- so-called "lie detectors"--are typically based on detecting autonomic reactions and are considered unreliable (see "The polygraph in doubt"). That's why psychologists have been cataloging clues to deception--such as facial expressions, body language and linguistics--to help hook the dishonest.
Sometimes people lie in order to gain access to people and opportunities that improve their situation in life. For example, someone might lie on their resume and say that they have worked in publishing for 10 years when they have really only worked in the field for five.
Research indicates pathological lying can occur because of low self-esteem and a false sense of self. People who lie pathologically may want others to view them positively, making things up to make them look better. Their desire to create a false sense of self could indicate that they are unhappy with themselves.
Look for flared nostrils, lip biting, rapid blinking or sweating. These changes in facial activity signify an increase in brain activity as a lie begins. Some people will get a slight flush to their face when they are lying, so look for blushed cheeks as anxiety may set in.
Many NLP practitioners claim that a person's eye-movements can reveal a useful insight into whether they are lying or telling the truth. According to this notion, looking up to the right is indicative of lying whereas looking up to their left suggests that they are telling the truth.
Lying leads to psychological arousal, which in turn creates physiological arousal. The polygraph measures physiological responses that correspond to this arousal: galvanic skin response, respiration, heart rate, and relative blood pressure.
Personality disorders and pathological lying
Pathological lying or lying compulsively can also be a symptom of antisocial personality disorder or narcissistic personality disorder. People with these personality disorders may lie to gain sympathy or social status, or to preserve a false sense of self.
Signs of Lying
Repeating questions before answering them. Speaking in sentence fragments. Failing to provide specific details when a story is challenged. Grooming behaviors such as playing with hair or pressing fingers to lips.
People who lie repeatedly often have a desire to be in control. When the truth of a situation doesn't agree with such control, they produce a lie that does conform to the narrative they desire. Such people may also worry they won't be respected if the truth can leave them looking poorly.
The three most commonly referred to are lies of commission, lies of omission, and lies of influence, aka character lies.
They alter our reality, reframing it through the agenda of the person who doesn't want the truth to come out. Being lied to makes you feel insecure – your version of the truth is discredited. It also makes you feel unimportant – the person lying to you didn't value you enough to tell the truth.
This behavior can be part of a personality disorder such as antisocial, narcissistic, and histrionic. Other conditions, such as borderline personality disorder, may also lead to frequent lies, but these aren't considered pathological.
The narcissistic liar
This type of person never admits to making a mistake, even when the mistake could be a growth opportunity for your PR team. He or she is often a "people person" seeking attention when things go right, bragging or exaggerating accomplishments, while being quick to place blame and criticize others.
While pathological lying isn't a defining feature of anxiety as it is with other disorders, such as NPD, anxiety and compulsive lying can sometimes go hand in hand. People with anxiety disorders may lie to protect themselves from anxiety triggers or to handle things like a fear of rejection.
People who are more manipulative (as measured by a Machiavellianism scale and a measure of Social Adroitness) lie more often than people who are less manipulative. Manipulative people tend to care about themselves, so you might also think that liars are generally people who do not care about other people.
Lying, like other signs and symptoms of the condition, tends to occur because the person with BPD is unable to regulate their feelings and impulses. It's an act borne out of pain and fear. Often, people with BPD even believe their own lies.
Many people with BPD act impulsively, have intense emotions, and experience dissociation and paranoia when most distressed. This emotional volatility can cause relationship turmoil. Also, the inability to self-soothe can lead to impulsive, reckless behavior. People with BPD are often on edge.
Fear microexpressions: Microexpressions are brief, involuntary facial expressions that give away a person's true emotions. Liars are often afraid of being caught, so they may express fear through small movements, like raising their eyebrows or wrinkling their forehead.
All this deciding and self-control implies that lying is managed by the prefrontal cortex—the region at the front of the brain responsible for executive control, which includes such processes as planning and regulating emotions and behavior.
Becoming angry and defensive
If they feel that someone closes in on their lies and raises questions, liars tend to get angry and defensive. Even if no one is outright accusing them, they have an overblown reaction due to their fear of being caught.