Short abstract (98 words). Reasoning is generally seen as a means to improve knowledge and make better decisions. However, much evidence shows that reasoning often leads to epistemic distortions and poor decisions. This suggests that the function of reasoning should be rethought. Our hypothesis is that the function of reasoning is argumentative. It is to devise and evaluate arguments intended to persuade. Reasoning so conceived is adaptive given humans’ exceptional dependence on communication and vulnerability to misinformation. A wide range of (...) evidence in the psychology of reasoning and decision making can be reinterpreted and better explained in the light of this hypothesis. (shrink)

Often, when several norms are present and may be in conflict, individuals will display a self-serving bias, privileging the norm that best serves their interests. Xiao and Bicchieri (J Econ Psychol 31(3):456–470, 2010) tested the effects of inequality on reciprocating behavior in trust games and showed that—when inequality increases—reciprocity loses its appeal. They hypothesized that self-serving biases in choosing to privilege a particular social norm occur when the choice of that norm is publicly justifiable as reasonable, even if not optimal (...) for one of the parties. In line with the literature on motivated reasoning, this justification should find some degree of support among third parties. The results of our experimental survey of third parties support the hypothesis that biases are not always unilateral selfish assessments. Instead, they occur when the choice to favor a particular norm is supported by a shared sense that it is a reasonable and justifiable choice. (shrink)