2016 年 14 巻 2 号 p. 149-154
Human well-being or happiness is affected by various elements. Well-being is not only determined by the degree to which individuals can meet their basic physical needs, but also how individuals behave. An example is the effect of altruistic behaviors, which are defined as putting others' needs before one's own. Why do altruistic behaviors contribute to a greater sense of well-being in agents? Based on the theoretical account of the role of altruistic behaviors in biological adaptation, it was hypothesized in this study that enhancement of biological fitness underlies subjective well-being. It is important to note that, in theory, the adaptive role of altruistic behaviors differs depending on the recipients. Kin selection and reciprocity underlie altruistic behaviors toward family members and others, respectively. In particular, altruistic behaviors toward non-family members are predicted to increase the fitness of the agents through reciprocal interactions with others; however, altruistic behaviors toward family members may not necessarily have the same effect on agents. To test the possibility that altruistic behaviors might affect well-being differently depending on the recipient, a survey was conducted using self-report scales on subjective well-being and daily altruistic acts toward family members, friends, and strangers. As a control variable or moderator, subjective socioeconomic status was also measured. As predicted, the results indicated that altruistic behaviors toward non-family members positively affected subjective well-being, but those toward family members did not. This effect was particularly prominent among individuals with a relatively lower subjective socioeconomic status. These findings indicate that a lifestyle based on direct and indirect reciprocal interactions results in increased well-being. Accordingly, the present study suggests that subjective well-being and biological adaptation are intimately connected.