European Journal of Social Psychology Eur. J. Soc. Psychol. 32, 35±56 2002) DOI: 10.1002/ejsp.74 The dissemination of critical, unshared information in decision-making groups: the effects of pre-discussion dissent FELIX C. BRODBECK, 1 * RUDOLF KERSCHREITER, 2 ANDREAS MOJZISCH, 2 DIETER FREY, 2 AND STEFAN SCHULZ-HARDT 2 1 Aston University, UK 2 Ludwig-Maximilians-University, Munich, Germany Abstract Previous research in group decision making has found that in situations of a hidden pro®le i.e. the best choice alternative is hidden from individual members as they consider their pre-discussion information), unshared information is disproportionately neglected and sub-optimal group choices are highly likely. In an experimental study, three-person groups decided which of three candidates to select for a professorial appointment. We hypothesised that minority dissent in pre-discussion preferences improves the consideration of unshared information in groups and increases the discovery rate of hidden pro®les. As predicted, consideration of unshared information increased with minority dissent. The expectation of an improvement of group decision quality was partially supported. In diversity groups i.e. each member prefers a different alternative) consideration of unshared information and group decision quality was signi®cantly higher than in simple minority groups. Results are discussed in the light of theories of minority in¯uence. The bene®ts of using the hidden pro®le paradigm with minority and diversity groups for theory development in the area of group decision making are highlighted. Copyright # 2002 John Wiley & Sons, Ltd. INTRODUCTION Groups are often employed for decision making because it is assumed that they can bring more intellectual resources to bear on a decision problem than individuals, thereby increasing the probability that group decisions are higher in quality than individual decisions. However, the history of group research documents numerous times when group performance in decision-making is sub- optimal for reviews see, e.g. Hill, 1982; Hinsz, 1990; McGrath, 1984; Steiner, 1972). For instance, we have known for decades that majorities win right or wrong, whether it comes from research on Received 8 July 2000 Copyright # 2002 John Wiley & Sons, Ltd. Accepted 7 June 2001 *Correspondence to: Felix C. Brodbeck, Organisations Studies Group, Aston Business School, Aston University, Birmingham B4 7ET, UK. E-mail: f.c.brodbeck@aston.ac.uk