Impact Bias in Regret: Comparisons Between Within-Subjects and Between-Subjects Designs, Kokaishita and Kuyashi, and the Presence and Absence of Reward1,2

When people anticipate future regret, they overestimate its strength compared to experienced regret. Two experiments investigated this impact bias of regret by manipulating regret type (anticipated/experienced) in a within-subjects design. Regret was measured using the Japanese words kokaishita (後悔した) and kuyashi (悔しい), which are both translated as “regret” in English but differ in nuance in Japanese. We compared the participants' feelings of kokaishita and kuyashi when they failed at tasks in which their decisions did or did not affect the outcome. In Experiment 1 but not Experiment 2, the participants were offered an additional reward for task success. The results suggested that (a) impact bias occurs robustly when the same person both anticipates and experiences regret; (b) kokaishita is felt in response to decision failures, while kuyashi is felt for any kind of task failure; and (c) the presence of additional rewards influences the intensity of kokaishita but not that of kuyashi or impact bias.