Upstream reciprocity refers to a person who has received help helping a third person instead of the person who helped him/her. It is observed widely but lacks a theory explaining its mechanism. Theory suggests that upstream reciprocity cannot maintain stable cooperation. Here we examine the possibility that the strength of a belief in a just world, which is a cognitive bias, drives upstream reciprocity. We test the effects on upstream reciprocity of a belief in a just world by conducting an upstream reciprocity game based on a trust game. The results demonstrate that upstream reciprocity is explained by a belief in immanent justice, a subconcept of a belief in a just world. These results shed light on a mechanism that explains why upstream reciprocity is observed in the real world.

Repeated help-seeking from the same helper produces gradually stronger hesitation. Therefore, switching helpers in one’s social network could be an effective strategy. We conducted an online experiment to examine whether people feel less stressed if they switch helpers in a repeated help-seeking situation. After reading a vignette about a stressful situation (depression or unemployment), participants judged the level of stress and chose a helper in their social network. Participants then received feedback that the situation had not improved even after help had been given and repeated the choice five times. The results showed that participants perceived lower stress in both depression and unemployment situations if they sought help from a greater number of helpers after controlling for social network size and diversity of helpers. The effectiveness of switching helpers and its mechanisms are discussed.

The items left by the deceased are often referred to as inherited items, of which those of particular importance are sometimes called mementos. In this study, to examine our predictions that some of the meaning bereaved families find in mementos are related to their continuing bonds with the deceased, we asked 250 adult men and women who had experienced the deaths of people important to them to cooperate in a questionnaire. It was shown that a memento mainly contains four meanings: 1) substance/functionality, 2) emotional/relationship-oriented, 3) respect for the will, and 4) symbolic of loss. Of these, 2) emotional/relationship-oriented and 3) respect for the will are positively related to the continuing bonds. These suggest that the meaning a bereaved family finds in a memento may be a rough indication of the progress of mourning.