Free ranking vs. rank-choosing: New insights on the conjunction fallacy

Abstract

It has been consistently shown that when asked to rank options, people often make fallacious judgements. Furthermore, such fallacies can be sensitive to presentation mode. In the first study, we explored a novel type of ranking presentation, namely, choosing between two rank orders of options. To enable a direct comparison of fallacy rates between free ranking and the new presentation mode, we calculated the frequencies of the two presented rank orders in a free ranking condition. Our analysis shows that people choose the non-fallacious rank order significantly more when asked to choose between two rank orders as compared to freely ranking the possible options. In a second study, we explored whether an agent presenting the rankings to choose from has an effect. To alleviate social biases we used videos of social robots as the presenting agents. We show that rank orders presented by social agents significantly reduce the fallacy rates, compared to rank orders presented without an agent. We discuss the results in view of social decision making theories, wherein a ranking presentation by a social agent is comparable to a consultation with another person regarding free ranking. Our results suggest that fallacious decision making can be mitigated by a social agent presenting rankings to choose from.