The Prisoner’s Dilemma and How It Affects Your Life

The Prisoner’s Dilemma is a very famous game in Game Theory. It has been much written and spoken about. Due to its mathematical nature many academic studies use it to understand side effects in people’s behavior today.

The game has many versions. In the original version two suspects, Mr. A and Mr. B are arrested by the police. The police have insufficient evidence for a conviction, so the prisoners are separated and offered the same deal.

  • If one testifies for the prosecution against the other (defects) and the latter remains silent (cooperates), the defector goes free and the silent accomplice receives the full 20-year sentence.

  • If both remain silent, both prisoners are sentenced to only one year in jail for a minor charge (such as careless driving)

  • If each betrays the other, each receives a fifteen-year sentence (25% deduction in appreciation for your cooperation)

Each prisoner must choose to betray the other or to remain silent. Each one is assured that the other would not know about the betrayal before the end of the investigation.

How should the prisoners act?

Ostensibly, there is no dilemma. Each player must choose to remain silent and thus ensure the minimum sentence of one year. They may reap even one-third off for good behavior and Hop! They’re out. To understand the dilemma try to understand what was happening in the head of one of the prisoners, let’s say Mr. A.

When he thinks to himself what to choose he is trying to predict what Mr. B will choose


“If Mr. B will keep quiet it is better for me to talk – so I’ll be free. If Mr. B will talk, of course it’s better for me to talk and I will not get the maximum punishment.”

It seems that whatever choice Mr. B makes, Mr. A will talk. This game is of course symmetric, so the same applies to what Mr. B would think and choose.

Now, the game that seems quite simple becomes complicated and surprising. Both choose to speak (defect) and both end up in prison for many years.

The truth is that this result is completely expected. The nature of people is not altruistic and when someone is deciding on his best interests he will usually allow himself preference over his partner. (Of course there are exceptions such as parents and children, good friends, etc.) Mr. A and Mr. B naturally thought of their personal welfare which made them decide to speak and sit in jail for years.

Experts attribute the results to the fact that in both scenarios we lack knowledge of what the other chooses. Of course, if they could speak with each other they would agree to keep quiet and spend the one year imprisonment as mutual appreciation for the other’s cooperation. But when one does not know what the other chooses, he can only guess and we have already seen the result.

This game, like many others, may lighten many situations in our real time lives.
For example, if you ask a favor of your colleague, you have a reasonably good chance that he would be happy to help you. It is sometimes surprising what people would do for each other. Stay later at work or help a friend with their homework (even though you have already finished). Indeed, the world is beautiful.

However, when I try to cross a busy intersection, I am always astounded that people are not willing to slow down even for a moment to allow me to cross. The irony is that they might be exactly the same people who helped you at work, stay another hour and sacrificed leisure or rest to help you overcome the obstacle. Now, they will not even slow down and let you pass.


So what is happening here?
How can we explain the difference in human
behavior in the different situations?

Game Theory explains The Prisoner’s Dilemma in this way:


When the game is repeated, it is likely that people will cooperate with each other. However, if you play just once, people tend to do what is best for themselves.

Colleagues work together, and it’s likely that if you do a favor for someone he will be happy to return the favor. One good turn deserves another, right? After all, you see each other almost every day, your friend knows you and your good will is important to him.

However, crossing the intersection is a “one time game”. Since it is highly unlikely you’ll ever meet the driver that did or did not let you cross the intersection, the expected result is that he will pass you by, or as in The Prisoner’s Dilemma – defect.

People cooperate (most of the time) where the game has more than one round. Indeed, when people cooperate, the world seems to be a better place.

Enjoy.