Equality bias impairs collective decision-making across cultures

Ali Mahmoodi, Dan Bang, Karsten Olsen, Yuanyuan Aimee Zhao, Zhenhao Shi, Kristina Broberg, Shervin Safavi, Shihui Han, Majid Nili Ahmadabadi, Chris Frith, Andreas Roepstorff, Geraint Rees, Bahador Bahrami

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We tend to think that everyone deserves an equal say in a debate. This seemingly innocuous assumption can be damaging when we make decisions together as part of a group. To make optimal decisions, group members should weight their differing opinions according to how competent they are relative to one another; whenever they differ in competence, an equal weighting is suboptimal. Here, we asked how people deal with individual differences in competence in the context of a collective perceptual decision-making task. We developed a metric for estimating how participants weight their partner's opinion relative to their own and compared this weighting to an optimal benchmark. Replicated across three countries (Denmark, Iran, and China), we show that participants assigned nearly equal weights to each other's opinions regardless of true differences in their competence-even when informed by explicit feedback about their competence gap or under monetary incentives to maximize collective accuracy. This equality bias, whereby people behave as if they are as good or as bad as their partner, is particularly costly for a group when a competence gap separates its members.
Original languageEnglish
Pages (from-to)3835-3840
Number of pages6
Journal Proceedings of the National Academy of Sciences of the United States of America
Issue number12
Early online date9 Mar 2015
Publication statusPublished - 24 Mar 2015

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