Groups are consistently more accurate in telling truths from lies than individuals are, a new study finds.

Four experiments were designed, by University of Chicago Booth School of Business professor Nicholas Epley and Chicago Booth doctoral student Nadav Klein, in which groups consistently distinguished truth from lies more accurately, demonstrating that the group advantage in lie detection comes through the process of group discussion, not the product of a ‘wisdom of crowds’ effect.

In other words, groups were not simply maximizing the small amounts of accuracy contained among individual members, but were instead creating a different type of accuracy entirely.

“We find a consistent group advantage for detecting small ‘white’ lies as well as intentional, high-stakes lies told for personal gain,” says Epley. “This group advantage seems to come through the process of group discussion rather than statistical aggregation of individual opinions."

Truth vs. Lie Detection

According to the study, the modest accuracy rate of people who can detect deception is driven mostly by the tendency to detect truths, rather than lies. This has led other researchers to develop costly training programs that target individual lie detectors to increase accuracy.

Epley and Klein test a different strategy: asking individuals to detect lies as a group.

“Existing research demonstrates that increasing incentives for accuracy among lie detectors does not increase accuracy, but that increasing incentives for effective deception among lie tellers make lies easier to detect. Therefore, we did not manipulate lie detectors’ incentives to detect truth versus lies accurately, but instead asked participants to detect truths v. lies in low-stakes and high-stakes contexts for the lie tellers,” Epley says.

In the first two experiments, subjects watched videos of different statements from different speakers and guessed whether each statement was a truth or a lie, either individually or in three-person groups. The only difference between the two experiments was that in the second, researchers used different statements and also nearly doubled the sample size.

In both, results were replicated: groups were more accurate than individuals (61.7 percent and 60.3 percent group accuracy in Experiments 1 and 2, respectively, compared to 53.55 percent and 53.56 percent individual accuracy).

Simple Synergistic Approach

The third experiment tested whether the group advantage in lie detection applied to high-stakes and intentional lies. Groups were again more accurate, with 53.2 percent over 48.7 percent in individual accuracy.

The fourth experiment focused on two underlying reasons groups could better identify deception than individuals: first, group discussion could identify the most accurate person within a group which increases accuracy through a sorting mechanism; and secondly, group discussion could elicit observations about the target that provide information needed to make an accurate assessment.

“Interventions to improve lie detection typically focus on improving individual judgment, which is costly and generally ineffective,” Epley says. “Our findings suggest a cheap and simple synergistic approach of enabling group discussion before rendering a judgment."


Nadav Klein and Nicholas Epley Group discussion improves lie detection PNAS May 26, 2015 doi: 10.1073/pnas.1504048112

Photo: fictures/flickr

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