This article explains the limitations of various hypotheses proposed to explain altruistic behavior, focusing particularly on the like-attracts-like hypothesis.
Altruistic behavior refers to actions that provide help to others even when it entails personal loss. Common sense makes it difficult to understand why someone would voluntarily undertake something that results in loss. So why does this altruistic behavior occur? Scholars have conducted extensive research to explain this behavior and have proposed various hypotheses. Among them, the Like-Attracts-Like Hypothesis is a particularly compelling one. Let’s explore this hypothesis. First, we will consider what hypotheses existed before the emergence of the Birds of a Feather hypothesis and what their limitations were. Then, we will examine how the Birds of a Feather hypothesis, which emerged to overcome those limitations, explains them instead.
The kin selection hypothesis, which initially gained significant support, explains that altruistic behavior arises when individuals share genes with their kin, leading them to help and protect those related to them. Indeed, family members helping each other has been a common practice throughout history and across cultures. It is not common for family members to stand by idly when a relative faces hardship. For example, if a younger sibling incurs significant debt due to business failure, one might help them even knowing it could be detrimental. The kin selection hypothesis effectively explains such altruistic behavior within blood relations. However, it has limitations in explaining relationships beyond blood ties. Furthermore, in modern society, we interact and live alongside diverse individuals beyond our blood relatives. The kin selection hypothesis alone is insufficient to explain these varied human relationships.
The reciprocal altruism hypothesis addresses this gap. It posits that altruistic behavior arises because interactions between people are repeated. This is a hypothesis applicable to more general relationships beyond kinship. It is a hypothesis grounded in human rationality: if I help someone, they will likely try to help me in return; if I do not help, they will likely act similarly. In this case, the altruistic act performed for the other person becomes a concept akin to accumulating points for future reciprocation. Consequently, it has the advantage of easily explaining altruistic behavior in general relationships, even without familial bonds like those found in kinship. However, this hypothesis only applies to situations within small groups where continuous interaction occurs. In reality, altruistic behavior can be observed even within large groups where interactions are not repeated.
To address this limitation, the birds of a feather hypothesis emerged. People, whether by choice or circumstance, tend to gather with those of a similar kind. Here, “similar kind” refers not to physical traits but to mental characteristics. That is, people with similar ideas tend to gather together. Indeed, evolutionary biologist Jared Diamond has shown through research that the ideological correlation coefficient between spouses is very high. Therefore, selfish individuals tend to form groups with other selfish individuals, while altruistic individuals tend to form groups with other altruistic individuals. When altruistic individuals gather to form a group, altruistic behavior can emerge even within large-scale groups where sustained interaction is difficult. The birds of a feather hypothesis is highly useful as it provides a mechanism for altruistic behavior to persist within large-scale societies.
Since the society we belong to generally constitutes a large-scale group, the Birds of a Feather hypothesis is highly appropriate for explaining altruistic behavior. However, the hypothesis also has clear limitations. Namely, the broader the group boundary defined, the higher the likelihood that selfish and altruistic individuals will be mixed together. In such cases, distinguishing between selfish and altruistic groups becomes meaningless. Furthermore, the hypothesis dichotomizes humans into selfish and altruistic individuals, whereas in reality, most people exhibit a mixture of both traits. Therefore, if the group size in the birds of a feather hypothesis were defined more precisely and a pluralistic approach rather than a simple dichotomy were applied, it could become an excellent theory that better explains the phenomenon.
In conclusion, altruistic behavior plays a significant role in human society. Various hypotheses have been proposed to explain such behavior, and each provides useful explanations within specific contexts. However, to fully explain altruistic behavior, it is necessary to combine the strengths of multiple hypotheses while recognizing their limitations. The Like-Attracts-Like hypothesis, as part of this effort, makes an important contribution to understanding altruistic behavior even in large-scale societies. Research on altruistic behavior must continue, as it will enable a deeper understanding of the complexity and diversity of human society.
