In this blog post, we’ll examine why human altruistic behavior occurs based on the repetition-reciprocity hypothesis and explore its significance and limitations.
How can human altruism be explained?
Before studying humans from the perspective of evolutionary biology, there is one important assumption: that humans are inherently selfish. It is believed that humans live to pursue their own interests and have developed and evolved in that direction. Viewing the world from this perspective, acts of kindness—such as helping others—are hard to find, and even if they do exist, they are difficult to understand. However, in reality, it is not hard to find examples of people putting their kindness into action—such as those who jump onto subway tracks to save a life or those who continue to donate regularly despite their own financial struggles. So, how can human altruism be explained? One explanation comes from the repeated reciprocity hypothesis in game theory, which helps us understand why humans engage in altruistic behavior.
What does the Repeated Reciprocity Hypothesis mean?
First, let’s examine what the Repeated Reciprocity Hypothesis is. Simply put, the Repeated Reciprocity Hypothesis is a game theory concept based on the principle of “an eye for an eye, a tooth for a tooth.” This hypothesis contains two key elements: reciprocity and repetition. The first is conditional cooperation, which corresponds to reciprocity. The second is repetition, which refers to the fact that actions continue over a long period between two people. Because of the concept of conditional cooperation, the Repeated Reciprocity Hypothesis incorporates the principle of “an eye for an eye, a tooth for a tooth.” So, what does conditional cooperation mean? In game theory, conditional cooperation refers to the principle of reciprocity, where one begins the game in good faith and then responds to the opponent’s goodwill with goodwill and to their ill will with ill will. Since this explanation alone may be somewhat difficult to understand, let’s examine the repetition-reciprocity hypothesis through the following example.
There are two students, A and B, at Snu Elementary School. One day, A forgot to bring the scissors needed for art class. So A asked B, “Can I borrow your scissors?” B gladly accepted A’s request and lent him the scissors. The next day, B forgot to bring castanets for music class. So, B asked A to lend them some, and A, thinking, “Since B lent me the scissors yesterday, I should lend them to B too,” lent B the castanets. Viewed from the perspective of the Reciprocity Hypothesis, this situation can be described as an instance of “returning a favor with a favor.” Now, let’s look at the opposite case, where malice is met with malice.
This time, there are two students, C and D. One day, C lost his eraser and asked D to lend him one. However, D refused to lend him an eraser, which hurt C’s feelings. The next day, D ran out of pencil leads and asked C to lend him some. However, C refused, saying, “Since you didn’t lend me an eraser yesterday, I won’t lend you pencil leads today either.” This case is an example of “responding to ill will with ill will” as described in the repetition-reciprocity hypothesis.
As this example shows, conditional cooperation embodies the principle of “an eye for an eye, a tooth for a tooth.” Now, let’s examine the concept of repetition—the idea that the behavior must be sustained over time—through another example.
There are two soccer teams: Team E and Team F. The two teams built a friendship by playing soccer matches every week, and every other week, one team would prepare drinks to share with the other after the game. From the perspective of either Team E or Team F, one might think, “It’s a small sacrifice for our team to provide the drinks this week, but since the other team will provide them next week, we’re happy to do it this week.” It is precisely because of the assumption that they will continue playing soccer together in the future that this act of kindness—providing drinks—holds true.
Now, let’s assume that Team E entered a tournament. Team E faced Team G in the round of 16 and played a full 90-minute match. In this case, Team E does not extend the favor of buying drinks for Team G as well. The reason is that even if they bought drinks for Team G, there is almost no chance they would meet again later to have that favor returned. As these two examples show, the Repeated Reciprocity Hypothesis suggests that without a recurring relationship, it is difficult for such favors to occur.
The Insurance Principle and Limitations of the Repetition-Reciprocity Hypothesis
So far, we have examined reciprocity and repetition, the core elements of the repetition-reciprocity hypothesis. Now, let’s take it a step further and examine the insurance principle inherent in the repetition-reciprocity hypothesis through an example.
H and I are college students majoring in materials engineering. Since the two will attend the same university for more than four years, the principle of repetition holds true; let’s also assume that they adhere to the principle of reciprocity—that is, “an eye for an eye, a tooth for a tooth.” First, H excels at chemistry and rarely struggles to understand the material in chemistry classes, but is very weak in physics. On the other hand, I is good at physics but weak in chemistry. One day, H asked I to explain the mechanics section of physics, and I explained it thoroughly. The next day, I asked H to explain the section on atoms in chemistry, and H thought, “Since I taught me physics yesterday, I should teach him chemistry today,” and explained it to him.
In this way, H and I continuously make up for each other’s weaknesses through mutual goodwill. In the process, H will likely come to think, “If I want to continue learning physics—which I find difficult—from I, I’ll have to teach I about chemistry in return.” In other words, the reason H does I a favor is to gain a benefit for himself later on by receiving help from I when he needs it. Thus, the basic principle of insurance can also be seen as applicable to the repetition-reciprocity hypothesis.
What are the significance and limitations of the Repeated Reciprocity Hypothesis?
The Repeated Reciprocity Hypothesis explains the fundamental reason behind altruistic behavior as ultimately being an action taken for one’s own benefit. As we saw in the examples of conditional cooperation and the insurance principle, people do favors for others in the present because they anticipate the possibility that they themselves may need help in the future. In this regard, the repeated reciprocity hypothesis holds significant importance in that it provides a logical explanation for the question, “Why do humans engage in altruistic behavior?”—a question that is difficult to explain from the perspective of evolutionary biology.
However, while many studies recognize repeated reciprocity as a key theory for explaining human cooperation, it cannot account for all altruistic behavior on its own. This theory requires the premise that actions must be repeated consistently and also assumes that people actually adhere to the principle of conditional cooperation. Therefore, there are forms of altruistic behavior—such as acts of kindness in one-time interactions or anonymous donations—that are difficult to fully explain using the repeated reciprocity hypothesis alone. Such behaviors can be understood more broadly when considered alongside other theories, such as indirect reciprocity, reputation effects, group selection, and kin selection. Ultimately, while the repeated reciprocity hypothesis is a very important theory for explaining human altruism, a more comprehensive understanding of human altruistic behavior can be achieved by examining it in conjunction with other theories.
