Lie detector, truth serum, studying body language - science has long struggled to find a foolproof way to expose liars. In particular, to identify criminals during interrogations. Frankly speaking, so far there is no significant success on this path. All of the above methods do not work properly.

However, as the publication IFL Science, scientists have still come up with an indirect way to determine the lie accurately enough. Helping them to do this were the findings of previous studies, which showed that dishonesty and deception can strain the brain and require it to expend much more cognitive energy than telling the truth. Therefore, the researchers believe that it is possible to identify a liar by giving them a second task to perform at the same time they are answering questions. Trying to distribute brainpower between the two activities is likely to make the lie less nuanced, which means it will be easier to detect.

"Over the past 15 years, we have shown that lies can be detected by outsmarting liars. We have demonstrated that this can be achieved by getting liars to divide their attention between the wording of a statement and a secondary task," said Alder Wray, a professor in the Department of Psychology at the University of Portsmouth (UK), who authored the study. The work was published in the International Journal of Psychology and Behavior Analysis.

His group determined that truth and lies can sound equally believable if liars are given a good opportunity to think about what they are going to say. If they are deprived of that opportunity, however, it becomes much more difficult to come up with lies. "The lies in our experiment sounded less plausible than the truth, especially when the interviewees also had to perform a secondary task and were told that this task was important," explained Wray.

Researchers conducted the study among 164 people. They were first asked about their level of support or distrust on a variety of controversial topics in the news, from COVID passports and immigration to Brexit and Boris Johnson. Participants were then randomly assigned to the roles of truth tellers or liars. The former were asked to report their thoughts and feelings honestly, while the latter were asked to lie to the researchers.

The scientists had to guess who was telling them the truth and who was misleading. To incentivize the participants, they were told that they had a chance to win a cash prize if they could convince the scientists of their position. Two-thirds of the participants were asked to recall and give the license plate number of their car during the interview, among other things. Half of this group was also told that this task was particularly important.

The results of the experiment showed that the stories of liars were perceived as less believable and less clear than those of truth-tellers. This impression was especially reinforced when those who told untruths were given a secondary task and told that it was important.

"The pattern of results suggests that introducing secondary tasks in interviews can facilitate lie detection, but such tasks need to be introduced cautiously," Prof. Wray explained. According to him, the secondary task was only effective when liars took it seriously, not as a trivial matter.

To get the interviewee to take such a task seriously, they need to be persuaded that it is important, as was the case in the scientists' experiment, or introduce a secondary task that should not be neglected. Such a task could be grabbing an object, holding an object in the air, or driving a car simulator. If the side task does not meet these criteria, it is unlikely to help lie detection.

Earlier OBOZREVATEL told, what gestures can indicate that a person is lying.

Subscribe to OBOZREVATEL channels in Telegram and Viber to keep up to date.