Reaching Consensus in Polarized Moral Debates.

The group polarization phenomenon is a widespread human bias with no apparent geographical or cultural boundaries [1]. Although the conditions that breed extremism have been extensively studied [2-5], comparably little research has examined how to depolarize attitudes in people who already embrace extreme beliefs. Previous studies have shown that deliberating groups may shift toward more moderate opinions [6], but why deliberation is sometimes effective although other times it fails at eliciting consensus remains largely unknown. To investigate this, we performed a large-scale behavioral experiment with live crowds from two countries. Participants (N = 3,288 in study 1 and N = 582 in study 2) were presented with a set of moral scenarios and asked to judge the acceptability of a controversial action. Then they organized in groups of three and discussed their opinions to see whether they agreed on common values of acceptability. We found that groups succeeding at reaching consensus frequently had extreme participants with low confidence and a participant with a moderate view but high confidence. Quantitative analyses showed that these "confident grays" exerted the greatest weight on group judgements and suggest that consensus was driven by a mediation process [7, 8]. Overall, these findings shed light on the elements that allow human groups to resolve moral disagreement.