It is clear that lying in an interview consumes more cognitive energy than telling the truth. Now, a [new study] from the University of Portsmouth( https://pure.port.ac.uk/ws/portalfiles/portal/51361890/The_Effects_of_a_Secondary_Task.pdf ) It is found that investigators are more likely to expose swindlers by taking advantage of this knowledge by requiring suspects to perform additional and secondary tasks when questioned** The extra mental effort required to concentrate on a secondary task (other than lying) is particularly challenging for liars.
In this experiment, the secondary task used was to recall a seven digit car registration number. Secondary tasks are found to be effective only when the liar is guided to believe that it is important.
Professor aldert Vrij of the Department of psychology at the University of Portsmouth, who designed the experiment, said: "over the past 15 years, we have proved that lies can be found by defeating liars. We have proved that this can be achieved by forcing liars to share attention between making statements and a secondary task."
"Our research shows that as long as the liar is given a good chance to think about what to say, the truth and the lie sound equally credible. When there are fewer opportunities to think, the truth often sounds more credible than the lie. In our experiment, the lie doesn't sound as credible as the truth, especially when the respondent has to perform a secondary task and is told that the task is important."
The 164 participants in the experiment were first asked to give their support or opposition to various social topics in the news. Then, they were randomly assigned to the condition of truth or lie and interviewed on the three topics they felt most strongly. People who tell the truth are asked to report their true opinions, while people who lie are asked to lie about their opinions in the interview.
The person doing the secondary task was given a seven digit car registration number and asked to recall it to the interviewer. Half of them were given additional instructions, and if they could not remember the car registration number during the interview, they might be asked to write down their comments after the interview.
Participants have the opportunity to prepare for the interview and are told that it is important to be as convincing as possible in the interview - which is encouraged by participating in a lottery.
The results showed that the liar's story sounded less believable and clear than that of the truthful, especially when the liar was given a secondary task and told it was important.
Professor Vrij said: "the result model shows that the introduction of secondary tasks in the interview can promote lie detection, but the introduction of such tasks needs to be cautious. It seems that the secondary task will be effective only if the liar does not ignore it. To do this, either tell the respondents that the secondary task is important, as shown in this experiment, or introduce a secondary task that cannot be ignored (such as grasping an object, lifting an object into the air, or driving a car simulator). Secondary tasks that do not meet these criteria are unlikely to promote lie detection. "
The study was published in the International Journal of psychology and behavioral analysis.