从利益到本能:损人不利己、幸灾乐祸与助人为乐的统一解释

Spite, schadenfreude, and altruism are three seemingly contradictory human behaviors: the first harms others without benefiting the self, the second takes pleasure in others' misfortune, and the third sacrifices the self for others. Existing theories explain them separately using spite, social comparison, reciprocal altruism, and empathy, but they lack a unified underlying mechanism. This paper proposes an alternative framework: these three behaviors share the same underlying logic—the behavior itself directly brings mood reward, independent of material returns. This mechanism originated as a byproduct of causally instrumental self-interested behavior. Over a long cultural evolution, the causal chain was forgotten through civilizational consolidation, and the behavior itself became the end. This paper demonstrates the logical coherence of this framework and discusses its testable predictions. 损人不利己、幸灾乐祸与助人为乐是三种看似矛盾的人类行为:前者损害他人且无益于己,中者以他人不幸为乐,后者则牺牲自己成全他人。现有理论分别用“恶意”“社会比较”“互惠利他”和“共情”来解释它们,但缺乏一个统一的底层机制。本文提出一个替代框架:这三种行为共享同一底层逻辑——行为本身直接带来“心情收益”,无需依赖物质回报。这一机制最初是“有因果的利己行为”的副产品,经过漫长的文化演化,因果链条被“文明固化”所遗忘,行为本身成为目的。本文论证这一框架的逻辑自洽性,并讨论其可检验的预测。