Polygraph or a lie detector is not always 100 percent reliable. As it measures and records several physiological responses – such as heart rate, blood pressure, respiration, and skin conductivity – an innocent person may sometimes end up appearing as a liar. I know you can’t always have a lie detecting machine to hand, but how can you tell if someone is lying to you – watching just their body language?

The person you’re talking to is lying to you if he/she copies your body language closely and nods along in agreement. This is the conclusion of a new study carried out by a combined team of researchers from Aarhus University in Denmark and Arizona State University, USA. So if you suspect someone is lying about something, it would be wise to keep an eye on the person throughout the conversation.

In the study, the team monitored the speech patterns and movements of 92 participants, pixel by pixels, from video recordings of conversation between the participants. They found that those who had been told to lie to their conversation person closely adapted to the movement of the person they’re talking to more often. For example, nodding just after their conversation partner had done so.

“Our theory is that the participants who lied coordinated their movements with their conversation partner without thinking about it, to please them, either because they struggled to lie or to appear more convincing,” explained Riccardo Fusaroli, lecturer in cognitive science at the Department of Communication and Culture at Aarhus University, Denmark, in a news release.

First picture shows movement change across two sequential points in time, targeting head movements (gray boxes). Middle picture shows pixels that change from frame-to-frame are converted to a white dot for visualization purposes, producing motion energy flows. Bottom picture shows the number of pixels that change from frame-to-frame, repeated over the length of the video, are converted into a time series that captures degree of movement displacement for each participant.

For the study, the team used a method known as the ‘Devil’s Advocate’ method, where they gave each participant a questionnaire where they would describe their viewpoints on a number of controversial subjects such as “the death penalty, legalization of the hash and homosexuals’ right to marriage.” They then split the participants up, and asked to complete two exercises.

First, the team made each participant have a conversation with another participant for 8 minutes on a topic that they disagreed on. Second, they asked a participant to lie to their conversation partner during a discussion on another topic such as legalisation of the hash. Eight minute after the exercises was complete; the team interviewed each of the participants in a separate room.

“The purpose of the research is to gain insight into the coordination of speech rhythms and body language in the conversations involving deception and whether it’s significantly different from coordination in more honest conversation between the same people,” said Riccardo Fusaroli.

“Our research is aimed at better understanding social coordination. We often enact small deception, either strategically or to improve and maintain our relationships, so understanding what happens in those circumstances is important to understand how we function socially,” he explained. “Insights from this kind of research is often used to inspire intervention programs for people with social impairment, e.g. people on the autism spectrum or people with facial paralysis. However, there is little work on how we interact effectively when deception and conflict are present and these are important social skills that should be addressed.”

Fusaroli is not ready to use the “Devil’s Advocate” method for now, but he says the results are an interesting development in understanding how people communicate. He also adds that it’s not always it’s wrong to lie – it can be a way to ensure consistency with others.

The study, entitled Conversing with a devil’s advocate: Interpersonal coordination in deception and disagreement has been published in the journal PLOS ONE.

Source:  Videnskab.dk via ScienceNordic