Unlike Pinocchio, liars do not usually give signals that they are lying, and some have succeeded in deceiving lie detectors, until the FBI established the Department of Criminal Psychology in the 1970s.

Some of the tricks of this "security apparatus" to detect lies appeared in the new "Netflix" series, "Mind hunter". Behavioral and psychological research followed, which helped reveal the accused from the first interrogation session.


Professors from the Department of Psychology at the University of Portsmouth relied on the hypothesis that a liar consumes more cognitive energy than telling the truth, in a 15-year experiment, to uncover ways to expose lies during interrogations, and published their results in the "International Journal of Psychology and Behavioral Analysis" last month.

The results of the experiment showed the possibility of detecting lies by distracting the liar and asking him to perform a secondary task in addition to completing his narration.

The researchers asked participants assigned to lie to be persuasive, and lured them with valuable prizes.

During the interview, they were offered to read 7 numbers written on a piece of paper, then memorize and retrieve them, or else the prize would be lost, and they would have to write down their opinions after the interview.

The stories of the liars seemed less logical as soon as they tried to memorize the numbers, and the researchers set the condition for the success of the experiment in convincing the liar of the need to perform the secondary task (distraction factor), or by distracting him with a task that cannot be refused, such as: driving a car, carrying something, eating food or washing dishes.

The first lie detector trick is to ask the suspect to provide detailed statements about his or her activities (Shutterstock)

muscle spasms

The Journal of Nonverbal Behavior published the results of a study conducted by graduate students in the Department of Communication at the University of Buffalo, and supervised by a research scientist at the US Transportation Security Administration in 2011.

The researchers divided the participants into two groups, one lying and the other telling the truth, and examined whether the participants could prevent their facial expressions, such as raising and furrowing their eyebrows or smiling, even after the researchers asked them to stop them.

The participants in the truth group showed a superior ability to control their facial expressions, while most of the participants in the “liars” group reported that they succeeded in controlling their expressions, but they did not succeed in this completely, and incomprehensible and rapid muscle spasms appeared on the forehead and lips, and confirmed Researchers find that the upper part of the face is more difficult to control, and its spasms are a common sign of deception.

inappropriate expressions

The first comprehensive study of the secrets of the human face came after Michael White killed his pregnant wife, deceived the police and the general public, and claimed she had disappeared for weeks, in which he remained crying in front of the lenses of photographers.

The team of the Forensic Psychology Laboratory at Dalhousie University analyzed the features of the grieving husband's face, and found expressions of anger and disgust on his face at the time he sought help to search for his wife.

The team repeated the experiment on more than 60 videos of such crimes from Canada, the United States, Britain and Australia, and then applied their hypothesis to a number of study participants, and some inappropriate expressions appeared, such as smiling in front of disgusting pictures or blinking in front of a picture of a crying child.

The researchers noted that most inconsistent emotions usually appear either in the upper part or the lower part of the face only, and the researchers pointed out that the person should be asked about the reason for the feeling on his face.

The researchers note that most inconsistent emotions usually appear either at the top or bottom of the face only (Shutterstock)

open questions

The "Association for Psychological Sciences" stated that researchers from Columbia University suggested some verbal methods for detecting lies, backed by experiments between criminals and investigators.

The first lie detector trick is to ask the suspect to provide detailed statements about his or her activities through open-ended questions, such as "What did you do yesterday between 4 and 5 p.m.?"

This encourages the suspect's manner of speaking, allowing discrepancies between the answer and the available evidence to be identified.

The liar is expected to find the task difficult, will often give fewer details about the time and location, speak slowly, and make linguistic errors amid a lot of hesitation.

But the most powerful ploy indisputably was to impose a burden on him by asking him to recall the events in reverse, and that ploy proved effective in courtrooms and police interrogations.

unexpected questions

Liars expect questions that aim to verify their statements, and will prepare fabricated details to support their lies, and those prepared lies are more difficult to distinguish from the truth than lies of the moment, so unexpected questions may help to expose the professional liar.

And in 2009, a team at the University of Portsmouth uncovered an experiment in which they interviewed one-on-one liars and true story tellers about lunch at a specific restaurant.

The researchers asked typical opening questions that the liars expected, followed by questions they did not expect about food items, how they got to the address and floor of the restaurant, and a description of the place.

Experience confirmed that asking unexpected questions causes confusion to the liar and immediately shows his inability to devise an appropriate story in 80% of cases.

The researchers confirmed that more questions push the liar to weave more fake answers to prove his truth (Shutterstock)

Ask more questions

When the liar feels threatened by possible exposure, the liar donates new lies to support the original, creating layers of deception that prevent others from accessing the information he seeks to hide;

So researchers at the Center for Social Sciences in Berlin suggested straining the liar by asking more questions.

The researchers tested the limits of people's lies by placing them in situations that involve varying degrees of control and accountability, and referred to these limits as the "psychological cost of lying," which the liar incurs in trying to hide his lie.

The experience confirmed that more questions push the liar to weave more fake answers to prove his sincerity, but you will see him fall before you into a well of unconnected lies when you do not reward the "psychological cost" of lying.