The cost of richness: the effect of the size and diversity of decision sets on post-decision regret

Decision making is often made difficult by the knowledge that one has to live with the outcomes of one's choices and with the regret that these might engender. Formal theories propose that regret is proportional to the difference between the outcome of the option chosen and the expected outcome of the next best alternative that one may have chosen instead. It follows that the number of alternatives available for choice does not affect post-decisional regret. In this study, however, the authors proposed that regret is related to the comparison between the alternative chosen and the union of the positive attributes of the alternatives rejected. This general proposition yielded 2 hypotheses: (a) the larger number of alternatives from which one can choose and (b) the more diverse those alternatives are, the stronger the regret that an unsatisfactory choice would cause. These hypotheses were tested and supported by 4 experiments.