title: Equality bias impairs collective decision-making across cultures.
abstract: 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.
authors.affiliation: Control and Intelligent Processing Centre of Excellence, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, 14395-515 Tehran, Iran; School of Cognitive Science, Institute for Research in Fundamental Sciences, 19395-5746 Tehran, Iran;
authors.forename: Ali
authors.initials: A
authors.lastname: Mahmoodi
authors.affiliation: Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, United Kingdom; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, United Kingdom; The Interacting Minds Centre, Aarhus University, 8000 Aarhus, Denmark;
authors.forename: Dan
authors.initials: D
authors.lastname: Bang
authors.affiliation: The Interacting Minds Centre, Aarhus University, 8000 Aarhus, Denmark; Centre of Functionally Integrative Neuroscience, Aarhus University Hospital, 8000 Aarhus C, Denmark;
authors.forename: Karsten
authors.initials: K
authors.lastname: Olsen
authors.affiliation: Department of Psychology, Peking University, Beijing 100871, China;
authors.forename: Yuanyuan Aimee
authors.initials: YA
authors.lastname: Zhao
authors.affiliation: Annenberg Public Policy Center, University of Pennsylvania, Philadelphia, PA 19104-3806;
authors.forename: Zhenhao
authors.initials: Z
authors.lastname: Shi
authors.affiliation: Centre of Functionally Integrative Neuroscience, Aarhus University Hospital, 8000 Aarhus C, Denmark;
authors.forename: Kristina
authors.initials: K
authors.lastname: Broberg
authors.affiliation: School of Cognitive Science, Institute for Research in Fundamental Sciences, 19395-5746 Tehran, Iran; Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72012 Tubingen, Germany;
authors.forename: Shervin
authors.initials: S
authors.lastname: Safavi
authors.affiliation: Department of Psychology, Peking University, Beijing 100871, China;
authors.forename: Shihui
authors.initials: S
authors.lastname: Han
authors.affiliation: Control and Intelligent Processing Centre of Excellence, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, 14395-515 Tehran, Iran; School of Cognitive Science, Institute for Research in Fundamental Sciences, 19395-5746 Tehran, Iran;
authors.forename: Majid
authors.initials: M
authors.lastname: Nili Ahmadabadi
authors.affiliation: The Interacting Minds Centre, Aarhus University, 8000 Aarhus, Denmark; Centre of Functionally Integrative Neuroscience, Aarhus University Hospital, 8000 Aarhus C, Denmark; Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N 3BG, United Kingdom; and.
authors.forename: Chris D
authors.initials: CD
authors.lastname: Frith
authors.affiliation: The Interacting Minds Centre, Aarhus University, 8000 Aarhus, Denmark; Centre of Functionally Integrative Neuroscience, Aarhus University Hospital, 8000 Aarhus C, Denmark;
authors.forename: Andreas
authors.initials: A
authors.lastname: Roepstorff
authors.affiliation: Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N 3BG, United Kingdom; and Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, United Kingdom.
authors.forename: Geraint
authors.initials: G
authors.lastname: Rees
authors.affiliation: The Interacting Minds Centre, Aarhus University, 8000 Aarhus, Denmark; Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, United Kingdom bbahrami@ucl.ac.uk.
authors.forename: Bahador
authors.initials: B
authors.lastname: Bahrami
mesh_terms: D000328:Adult; D002681:China; D003071:Cognition; D003142:Communication; D003198:Computer Simulation; D003299:Cooperative Behavior; D003466:Cultural Characteristics; D003657:Decision Making; D003718:Denmark; D006801:Humans; D007398:Interpersonal Relations; D007492:Iran; D008297:Male; D011287:Prejudice; D015203:Reproducibility of Results; D012919:Social Behavior
keywords: bias; equality; joint decision-making; social cognition