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Science reveals the keys to detect a lie

Science reveals the keys to detect a lie

May 10, 2021

Psychology has gained popularity in the theory that, when it comes to detecting signs that the person talking to us is lying, it is good to look at the expressions on his face. That is to say, that taking into account the non-verbal language that is expressed through face gestures is necessary to know if someone is telling the truth or not.

The idea is that there are some signals, calls facial microexpressions, that appear in different points of the face and that are so discrete, automatic and involuntary that reveal aspects about the true intentions and motivations of the person .

However, a recent study calls into question this idea by pointing out that when it comes to detecting lies, the less the other person's face is seen, the better. That is stop paying attention to these visual signals can be useful when approaching the truth .


A study focused on the detection of lies

This investigation was promoted by political issues: there are proposals not to allow witnesses to wear garments associated with the Muslim religion such as the niqab, which covers the entire head and exposes only the eyes of the woman.

That is, we wanted to see to what extent the reasons for prohibiting this were reasonable and based on objective facts related to the way in which we can detect the lies. For this, a series of research teams from the University of Ontario and the University of Amsterdam coordinated their efforts to examine this issue in the laboratory.


How was the experiment performed?

The study had two types of experiments in which a series of volunteers had to say if several women who acted as witnesses told the truth in a sham trial. To make it more realistic, each of the witnesses was shown a video showing a person stealing a bag or not, so that each of them saw only one of the two versions of what could happen: or had been stolen , or not. In addition, they were told that they should testify about the behavior they had seen and that half of them had to lie about what happened.

During the interrogation at the trial, some of the witnesses wore a hijab, which covers parts of the head but leaves the face exposed; others carried the aforementioned niqab that only reveals the eyes of the wearer, and others wore clothes that did not cover the head. These trials were filmed and then shown to students from Canada, the United Kingdom and the Netherlands. They had to find out who was lying and who was telling the truth .


The results: the less you see, the better to know who is lying

The results, published in the journal Law and Human Behavior, were surprising. Curiously, the students were more adept at detecting the lies when they had to judge women with almost all their faces covered . That is, it was easier to be right about what women thought when they wore hijab and, to a lesser extent, niqab. Women who had no part of their head covered were always "discovered" to a lesser degree than others. In fact, with them it happened that they were recognized as witnesses who lied by pure luck, since the success rate did not take off significantly of 50%.

This not only went against the logic of making more accurate judgments the more information we have, but it also indicated that negative stereotypes about Muslim women did not lead to more less favorable judgments about them.

Possible explanations for this phenomenon

What do these results mean? One way to interpret them is to assume that the non-verbal cues we take into account (even if unconsciously) when judging the truth of what is heard distract us more than anything else , causing us to reach false conclusions for supporting irrelevant information.

For this reason, the barriers that cover facial expressions cause us to be forced to direct our attention to more reliable and relevant sources of information, such as the tone of voice, the frequency with which grammatical errors are made, the tremor of the voice, etc. . In fact, some of the students were directly placed in a position where they could not see the screen on which the video was seen when it was their turn to detect the possible lies of veiled women, so as not to be distracted.


The language of lying — Noah Zandan (May 2021).


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