The Less You Know, You Think You Know More; Dunning and Kruger effect in Collective Decision Making


Resolving disagreements by collective decision making requires knowledge about task and others’ opinion quality. We tested dyads in a visual discrimination task to first show confidence of their individual decision and in case of disagreement announce their joint decision. Using a Bayesian approach, for each participant we compared the optimal decision rule (i.e. relative reliability of participant’s own opinion to that of his partner) to the empirically obtained (fitted) decision rule. The less sensitive observers (i.e. the ones who made poorer individual decisions) were significantly less successful in group decision making compared to their more sensitive partners. These less sensitive observers insisted on their individual decision as the group decision more often than recommended by the optimal decision rule. Our findings extent the previously found Dunning-Kruger effect to social decision making domain: the more incompetent are often less aware of their greater fallibility

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