In this blog post, we’ll examine the meaning, characteristics, and limitations of the “Birds of a Feather Hypothesis,” one of the leading theories explaining human altruistic behavior.
You’ve likely seen celebrities or athletes in the media facing criticism after being embroiled in controversies over their character. Conversely, we often encounter instances where people inspire admiration through acts of kindness performed without expecting anything in return. While we often admire celebrities—often called “charity angels”—we also sometimes wonder, “What are they hoping to gain in return?”
Evolutionary theory explains that living organisms have evolved to maximize the survival rate of their own species. Therefore, from an evolutionary perspective, all living beings should act in a way that preserves their species. However, as seen in the examples discussed earlier, we can easily observe altruistic behavior in humans. Humans sometimes survive even while engaging in behavior that is disadvantageous to their own survival. For this reason, scholars began researching why altruistic behavior—which is difficult to explain solely from an evolutionary perspective—occurs in humans.
Based on various grounds, scholars have proposed diverse hypotheses to explain human altruism, which have been subject to mutual refutation or supplementation. One of these is the “birds of a feather flock together” hypothesis. Simply put, this means “like attracts like.” Scholars who support the “birds of a feather flock together” hypothesis have noted that people who share common religious or political views tend to form relationships with one another. They explain that this tendency has aided the survival of altruistic individuals. If altruistic people tend to gather with other altruistic people, and selfish people tend to gather with other selfish people, then ultimately, altruistic people will gain greater benefits by associating with one another.
When a selfish person encounters an altruistic person, the selfish person can gain a one-sided advantage. This is because while the selfish person takes no action for others, the altruistic person helps others at their own expense. Looking at this situation alone, one might conclude that in a society where selfish and altruistic people coexist, the number of selfish people is bound to increase over time.
However, the situation changes if we assume that altruistic individuals are more likely to encounter other altruistic individuals. Altruistic individuals can enhance each other’s well-being and maintain a kind of symbiotic relationship. Conversely, even when selfish individuals encounter one another, a state of inaction persists. Through this process, selfish individuals realize they are falling behind in the competition for survival and gradually begin to choose altruistic behaviors in order to form relationships with altruistic individuals. This process is similar to shifts in market trends. It follows the same principle as when a product must be adapted to move into a new mainstream market because the growth potential of the existing market is no longer significant.
The “Birds of a Feather” hypothesis ultimately explains the spread of altruistic individuals by positing that the process of people with similar tendencies clustering together transforms selfish individuals into altruistic ones. Since the results were derived by altering only the probability of transactions occurring—while maintaining the existing transaction patterns between selfish and altruistic individuals—this hypothesis does not significantly contradict basic evolutionary theory. Furthermore, because it presents a model that explains the emergence of altruistic individuals while maintaining an evolutionary framework, it is considered a hypothesis that is relatively easy to combine with or extend to other theories.
Although the “Birds of a Feather” hypothesis can explain altruistic behavior in humans, it also has several distinct limitations. According to this hypothesis, humans ultimately form relationships with those similar to themselves and gradually converge into a single homogeneous group with similar tendencies. Therefore, if a situation arises that could disrupt an altruistic group, that group could collapse very easily. Furthermore, while the “Birds of a Feather” hypothesis may explain the survival of altruistic individuals, it does not sufficiently explain how “diversity”—a key driving force behind the development of human society—is maintained.
However, the “birds of a feather flock together” hypothesis has the advantage of being broadly combinable simply by applying the element of “transaction probability” to various other hypotheses. This characteristic can greatly aid in developing more complex theories and will ultimately bring us one step closer to a more complete theory explaining why altruistic behavior arises in humans.
