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Groups can make better decisions than individuals when members cooperatively exchange and integrate their uniquely held information and insights. However, under conformity pressures group members are biased towards exchanging commonly known information, and away from exchanging unique information, thus undermining group decision-making quality. At the neurobiological level, conformity associates with the neuropeptide oxytocin. A double-blind placebo controlled study found no evidence for oxytocin induced conformity. Compared to placebo groups, three-person groups whose members received intranasal oxytocin, focused more on unique information (i) and repeated this information more often (ii). These findings reveal oxytocin as a neurobiological driver of group decision-making processes.

Group discussion often becomes one-sided and confirmatory, with poor decisions as the unfortunate outcome. Here we examine whether intergroup competition amplifies or mitigates effects of individual versus team reward on information sharing biases and group decision quality. Individuals (N = 309) in 103 interacting groups were given private information on four decision alternatives and discussed a joint decision. Private information was distributed such that groups faced a “hidden profile” in which pushing for initial preferences and commonly held information prohibits the group from finding the best alternative. Group members were rewarded for team or individual performance, and groups faced intergroup competition or not. Whereas intergroup competition did not influence common-information bias, we find that when intergroup competition is absent, groups under individual (versus team) reward have stronger preference-consistency bias and make poorer decisions. When intergroup competition is present, however, groups under individual reward perform as good as groups under team reward. Results resonate with the possibility that intergroup competition overshadows within-group rivalry, and can promote even-handed discussions within small groups of decision-makers.