Inoue, Y.(井上裕香子), Mifune, N.(三船恒裕), & Saijo, T. (2023). 
Positive reputation for altruism toward future generations regardless of the cost for current others. 
Frontiers in Psychology, 13: 895619.

Recently, altruism toward future generations (future altruism) has become a hot research topic. Although future altruism has been observed in several previous experiments, it is not yet clear when and why people are more likely to engage in future altruism. Drawing upon the empirical literature of reputation and cooperation, we predicted that future altruism brings reputational disadvantages. Accordingly, we investigated whether future altruism was evaluated positively or negatively by others in the current generation in two vignette studies (total N = 1,237). Contrary to our initial prediction, we found that future altruism was positively evaluated even when it decreased the payoff of the members of the current generation. The difference in the evaluation of future altruism, as opposed to unsustainable current-generation focused behavior, was most pronounced when people do not know how a future altruist allocates rewards among individuals in the current generation. However, the positive evaluation of future altruism did not stem from the expectation that future altruists would also be altruistic toward the current generation. These results indicated that reputational benefits (i.e., positive reputation from others in the current generation) promote future altruism.

そこで本研究では、ISDG(Kamijo et al., 2017) という将来世代への利他行動を測定する経済ゲームを用い、意思決定者を評価させる場面想定法課題をオンラインで実施した。具体的には、意思決定者が将来世代に利他的な選択をすると、評価者である参加者を含めた「現世代全体」の利益が減る状況で、将来世代に利他的な選択をした意思決定者と現世代の利益を最大化する選択をした意思決定者それぞれを参加者に評価させた。その結果、将来世代に利他的な意思決定者の方がより高く評価された。ただし、意思決定者が「現世代全体」の利益をその後どう世代内で分配したかという情報を追加すると、将来世代への意思決定が評価に及ぼす効果が小さくなった。