In this blog post, we’ll examine how the Repeated Reciprocity Hypothesis can explain altruistic behavior in living organisms.
In a famous scene from the hugely popular 2009 Korean film ‘Haeundae’, marine rescue worker Hyeong-sik (played by Lee Min-ki) risks his life to rescue people from a whirlpool at sea and ultimately sacrifices himself for others. In this way, people engage in altruistic behavior for others, whether they have a direct connection to them or not. Beyond such dramatic examples, we commonly see behaviors—such as donations, blood drives, and volunteer work—that incur costs but offer no clear personal benefit. These behaviors are also observed in animals. Even in animals like chimpanzees, altruistic behaviors that benefit others—such as sharing food with peers or grooming them—are frequently observed.
If self-interest were always more advantageous than altruism, there would be no reason for living beings to act altruistically. In that case, most living beings would act selfishly. However, this is not the case in reality. Living beings do not solely consider their own interests and make only choices that benefit themselves. So how does altruism persist in living beings? One theory that explains this is the “Repeated Reciprocity Hypothesis.”
What is the repeated reciprocity hypothesis? In tribal societies of the past that relied on hunting for survival, those who failed to hunt might have faced the risk of starving to death. However, they could reduce this risk by having successful hunters share their food with those who failed, and in turn, receive help when they themselves failed to hunt. Living beings cannot solve all their problems alone as they go through life. While some problems can be solved independently, there are times when failure makes it necessary to seek help from others. Conversely, there are also times when one succeeds and is able to help others. Through such altruistic and reciprocal relationships—where help is exchanged when needed—both parties can increase their benefits and reduce risks.
So what happens if someone only accepts help from others without giving anything back? Wouldn’t the altruistic individual who offers help be at a disadvantage compared to the selfish individual who only takes? According to the Reciprocity Hypothesis, individuals act according to the principle: “If the other helps me, I will help them; if the other does not help me, I will not help them.” In a group that acts under this principle, even if a selfish individual initially exploits the goodwill of others, once this situation repeats itself, the other individuals will no longer extend goodwill toward them. Ultimately, in the long run, the selfish individual becomes isolated and is unable to receive help when needed. In contrast, an individual who returns favors in kind can receive help when needed, commensurate with the favors they have extended. Furthermore, if the other party does not help them, they simply need not help the other party in return, thereby minimizing their own losses. For these reasons, a selfish strategy becomes disadvantageous, while acting altruistically toward one another becomes the more advantageous strategy for survival.
However, for the repeated reciprocity hypothesis to hold true, repeated interactions must occur. If individuals meet only once and the likelihood of meeting again is nonexistent or very low, their motivation to act altruistically decreases because even if they choose to pursue only their own interests rather than cooperate, the other party has no opportunity to retaliate.
A prime example of this repeated reciprocity hypothesis is the vampire bat. In colonies of vampire bats, it has been observed that bats that have successfully obtained food regurgitate the blood they have consumed to share it with hungry bats that have been unable to find food. If a well-fed bat A shares food with a hungry bat B, there is a higher probability that B will share food with A the next time A is unable to find food and becomes hungry. Conversely, if A refuses to help B when B is hungry, B will likewise refuse to help A when the roles are reversed. Therefore, sharing food with a hungry counterpart is the most advantageous choice for both A and B; acting selfishly by refusing to do so may increase the risk of starving later when one’s own circumstances change.
This situation applies not only to animals but also to humans. If you remember and celebrate a friend’s birthday, that friend is also likely to remember and celebrate yours. If Country A helps Country B during a war, the likelihood that Country B will help Country A should Country A later find itself at war increases. If you leave a generous tip at your favorite restaurant, you can expect better service on your next visit. Similarly, if a shop owner sells quality products at fair prices without overcharging, customers will continue to patronize the store, leading to greater long-term profits.
In summary, the Repeated Reciprocity Hypothesis explains that altruism is maintained because people cooperate based on the principle of “an eye for an eye, a tooth for a tooth.” In other words, the reason people cooperate is that they know if they free-ride, the other party will not help them in the future. This hypothesis—which posits that while people are fundamentally altruistic, they cooperate only when the other party cooperates—explains a significant portion of everyday human behavior. Furthermore, the simple principle that “altruistic behavior is rewarded and selfish behavior is punished” aligns well with the ideals of those who hope to see good rewarded and evil punished.
However, this hypothesis has the limitation that it holds true only in situations involving repeated interactions. Helping someone you are unlikely to meet again does not increase the likelihood that you will receive help in the future. It is difficult to expect direct benefits in the future from actions such as helping a stranger carry their luggage, donating to a Salvation Army kettle, or leaving a tip at a restaurant visited briefly while traveling abroad. In other words, the repeated reciprocity hypothesis alone cannot fully explain why living beings act altruistically. Therefore, it is necessary to consider other hypotheses that explain why altruistic behavior occurs even in situations where there is no repeated interaction. Although it is not a complete explanation, the repeated reciprocity hypothesis is significant for understanding altruism in living organisms because it demonstrates that altruistic behavior can ultimately be a strategy that benefits the individual as well.
