Research Shows Simple Method to Spot Lies

Ask a suspect to complete an additional activity while being questioned, and you're more likely to be able to determine whether they are telling the truth or not, according to research, which has demonstrated an easy approach to help detectives sort out liars.

Previous research has demonstrated that lying and being dishonest can tax the brain, requiring far more mental effort than just stating the truth. The researchers theorize that by giving a person a second activity to complete while lying, they find it harder for them to generate the cognitive effort required to make up stories, making their lies less polished and more obvious.

"Over the past 15 years, we have demonstrated that it is possible to uncover lies by outwitting liars. By making liars split their attention between crafting a statement and a supporting task, we showed that this is possible, according to study author Professor Aldert Vrij of the University of Portsmouth's Department of Psychology.

Our research has demonstrated that as long as liars are given adequate time to consider their next move, both the truth and a lie can sound credible. Truths can sound more convincing than lies when one has less time to think. In our experiment, lies sounded less credible than truths, especially when the interviewees also had to complete a secondary task and were informed that this task was crucial.

The information comes from a study conducted by psychologists at the University of Portsmouth in the UK and published in the International Journal of Psychology & Behaviour Analysis.

164 participants were recruited by the team to participate in an experience that began with questions on their levels of support or opposition for different hot-button issues in the press, like COVID passports, immigration, Brexit, and Boris Johnson.

Following that, the participants were assigned at random to assume the roles of truth-tellers or liars. When asked about three of the issues, those who were telling the truth simply expressed their true opinions, whereas those who were lying made up their responses.

After that, the researchers had to determine who was telling the truth and who was lying. The participants were offered the chance to win $1,000 as an incentive if they were successful in persuading the researchers of their viewpoint. During the interview, two-thirds of the participants were asked to recall and memorize an automobile registration number. The fact that this assignment was very crucial was also disclosed to half of this group.

Overall, the findings demonstrated that people believed lies to be less credible and less understandable than truthful accounts, particularly when those who told lies were given the lesser-important secondary assignment.

"The results pattern suggests that the introduction of secondary tasks in an interview could facilitate lie detection, but such tasks need to be introduced carefully," said Professor Vrij.

A secondary task appears to only be effective if liars don't ignore it. This can be accomplished by either emphasizing the importance of the secondary task to interviewees, as was done in this experiment, or by introducing a secondary job that cannot be skipped (such as holding an object in the air, grabbing it, or operating a car simulator). These requirements must be met for secondary tasks to be helpful in lie detection.

Participants were asked if they would tell the truth or lie regarding various societal issues. During the interview, two-thirds of the participants were asked to recall and memorize an automobile registration number.

This secondary task was elevated in importance for one-third of the participants (secondary task and reward). The pre-registered hypothesis we investigated was that the secondary task and incentive condition would show the most pronounced differences between truth-tellers and liars, followed by the control condition (no secondary task) and the secondary task without an incentive condition.

The number of words said the number of reasons presented, and the plausibility, immediacy, directness, and clarity of the statement were the dependent variables.

It appears that for a secondary task to be successful, the primary objective must not be neglected by liars. This can be accomplished in two ways: either interviewees are informed that the secondary task is crucial (as we did in the current experiment), or a secondary task is presented that interviewees are unable to ignore (such as holding an object in the air, grasping it, or operating a driving simulator). Secondary tasks that do not meet these requirements are not likely to make it easier to discern the difference between the truth and lies.