A New Method of Lie Detection Exposes Liars by Distraction

Science -- July 5, 2022: According to a new technique for lying detection, people who are forced to multitask while being interrogated are more likely to lie.

University of Portsmouth is the source.
Summary:
It is commonly known that telling the truth during an interview requires less mental effort than lying. According to a recent study, detectives who took advantage of this discovery by having a suspect complete an additional, unrelated job while being questioned were more likely to identify liars. The extra brain power needed to concentrate on a secondary task (other than lying) was particularly challenging for lie tellers.
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According to a new technique for lying detection, people who are forced to multitask while being interrogated tend to utter lies more readily.

It is commonly known that telling the truth during an interview requires less mental effort than lying. According to a recent research from the University of Portsmouth, detectives who took advantage of this discovery by having a suspect complete a second, unrelated job while being questioned were more likely to catch liars in the act. For lie tellers, it was particularly difficult to focus on a secondary task (other than lying) since it required more mental energy.

This experiment's secondary task required participants to recall a seven-digit vehicle registration number. Only when lie tellers were made aware of the significance of the secondary assignment did it prove to be effective.

The experiment's creator, Professor Aldert Vrij of the University of Portsmouth's Department of Psychology, said: "The pattern of results suggests that the introduction of secondary tasks in an interview could facilitate lie detection but such tasks need to be introduced carefully. It seems that a secondary task will only be effective if lie tellers do not neglect it. This can be achieved by either telling interviewees that the secondary task is important, as demonstrated in this experiment, or by introducing a secondary task that cannot be neglected (such as gripping an object, holding an object into the air, or driving a car simulator). Secondary tasks that do not fulfil these criteria are unlikely to facilitate lie detection."

Prior to the experiment, the 164 participants were questioned about their levels of support or opposition for several societal issues that were currently making headlines. They were then asked about the three subjects that they felt most strongly about and randomly assigned to a truth or lying condition. During the interviews, truth tellers were told to express their genuine viewpoints, while liars were told to conceal their true beliefs.

Those doing the secondary task were given a seven-digit car registration number and instructed to recall it back to the interviewer. Half of them received additional instructions that if they could not remember the car registration number during the interview, they may be asked to write down their opinions after the interview.

The results revealed that lie tellers' stories sounded less plausible and less clear than truth tellers' stories, particularly when lie tellers were given the secondary task and told that it was important.

Professor Vrij said: "The pattern of results suggests that the introduction of secondary tasks in an interview could facilitate lie detection but such tasks need to be introduced carefully. It seems that a secondary task will only be effective if lie tellers do not neglect it. This can be achieved by either telling interviewees that the secondary task is important, as demonstrated in this experiment, or by introducing a secondary task that cannot be neglected (such as gripping an object, holding an object into the air, or driving a car simulator). Secondary tasks that do not fulfil these criteria are unlikely to facilitate lie detection."

In the International Journal of Psychology and Behaviour Analysis, the study was published.

Story Origin:

University of Portsmouth materials were provided. There may be length and style edits to the content.

Journal citation

Ronald P. Fisher, Haneen Deeb, Sharon Leal, and Aldert Vrij. A secondary task's effects on true and false opinion statements. The year 2022 issue of the International Journal of Psychology & Behavior Analysis DOI: 10.15344/2455-3867/2022/185
Reference this Page:
Portsmouth University MLA APA Chicago. A new technique for lie detection demonstrates that people forced to multitask while being interrogated are more likely to speak the truth. ScienceDaily. www.sciencedaily.com/releases/2022/05/220510151446.htm ScienceDaily, 10 May 2022.