The prisoner’s dilemma is one of the most famous illustrations of why people might act the way they do. The prisoner’s dilemma is actually a part of game theory, a field in mathematics that looks at various outcomes from situations that require strategy. However, the prisoner’s dilemma goes far beyond simply being a mathematical notion. It raises important questions about morality, psychology, and philosophy, and can even be observed in the real world.

In 1950, RAND Corporation hired mathematicians Merrill Flood and Melvin Dresher as part of their ongoing investigation into game theory and how it could be applied to global nuclear strategy. Based on the puzzles that Flood and Dresher created, Princeton professor Albert W. Tucker tweaked their work to make it more accessible to the masses, thus creating what is now known as the prisoner’s dilemma.

Two prisoners, prisoner A and prisoner B, are taken into custody. The police do not have a sufficient amount of evidence, so the decide to put A and B in separate rooms. The police officers tell each prisoner that if he turns in the other person and the other person remains silent, he will be able to go free while the prisoner who remained silent will face jail time. If both A and B confess, they will both have to face some jail time (though a shorter sentence than the one faced by the person who did not speak). If both prisoner A and B remain silent, they will both face an even shorter prison sentence.

For example:

According to this diagram, if prisoner A and prisoner B both confess, they will each have to serve six years. If prisoner A remains quiet while prisoner B confesses (which implicates prisoner A in the process), prisoner A has to serve ten years while prisoner B can go home. Likewise, if prisoner A confesses but prisoner B remains quiet, then prisoner A can go home while prisoner B faces ten years in prison. Lastly, if both remain quiet, they will each face two years. Another way we can view this is:

C represents a player cooperating (in this case, remaining silent) and D represents a player defecting (confessing). R stands for the reward that the players would receive if both decided to cooperate; P represents the punishment both players would receive for defecting; T is the temptation that a player would have for defecting alone; and lastly, S represents the “sucker” payoff that the player would have for cooperating alone.

The dilemma in the prisoner’s dilemma is this: Prisoner A and prisoner B are better off confessing; however, the outcome from having them both confess is much worse than it would have been if both had remained silent.

Prisoner’s dilemma is a perfect illustration of the conflict that arises between group rationality and individual rationality. If a group of people act rationally, they will actually do far worse than if a group of people acted irrationally. In the prisoner’s dilemma, it is assumed that all players are rational and know that the other player involved is rational. The rational thought would be to defect. But by choosing to protect themselves and acting in their own interest, the prisoners will actually be worse off.

Now, let’s add another option to the game. Players now have the option to defect, cooperate, or neither (N). We now see that defecting is no longer the dominant choice, and that the players will actually fare better by choosing to cooperate if the other player chooses neither.

The structure of prisoner’s dilemma can appear in grander settings, such as big groups or even societies. It is here that we see how morality comes into effect. Perhaps the best example to showcase a multiplayer prisoner’s dilemma is a situation known as the “tragedy of the commons.”

In the tragedy of the commons, a group of neighboring farmers all prefer that their cows not graze on their own individual properties (which are not very suitable), but on the commons. However, if the commons reaches a certain threshold, the land will become unsuitable for grazing. By acting rationally (in their own self-interest) and trying to reap the benefits of the land, the farmers will deplete the land and create a negative impact for everyone. Like prisoner’s dilemma, an individual rational strategy creates irrational outcomes that affect the group.

So what do the prisoner’s dilemma and tragedy of the commons tell us about morality? Essentially, these examples prove that pursuing one’s own self-interest and gratification will actually turn out to be self-defeating in the long run.

A classic example of the prisoner’s dilemma in the real world is currently a major issue in today’s fishing industry. Currently, industrial fishermen are catching fish at an extremely fast rate. While this might seem like it is good for current profits, the rate at which these fish are being caught is faster than the amount of time needed for the fish to reproduce. As a result, the fishermen now have a depleted supply of fish to choose from, thus creating a hardship for all fishermen.

In order to ensure the livelihood of the industry in the long term, fishermen should cooperate with one another and forgo high profits in the immediate future (thus, going against their own self-interest).