The Prisoners’ Dilemma

ImageAs the ever-wonderful xkcd comic above indicates, the Prisoners’ Dilemma is something that has passed into social and cultural circles, and is now well-known in popular psychology. The original “Prisoners’ Dilemma” was framed by Flood and Dresher in 1950. It is a canonical example of game theory that shows how sometimes, despite apparent mutual advantage, individuals refuse to cooperate with one another.

It was later formalised in terms of prison inmates by Alfred Tucker thus: “Two members of a criminal gang are arrested and imprisoned. Each prisoner is in solitary confinement with no means of speaking to or exchanging messages with the other. The police admit they don’t have enough evidence to convict the pair on the principal charge. They plan to sentence both to a year in prison on a lesser charge. Simultaneously, the police offer each prisoner a Faustian bargain. If he testifies against his partner, he will go free while the partner will get three years in prison on the main charge. Oh, yes, there is a catch: If both prisoners testify against each other, both will be sentenced to two years in jail.” As you see, the dilemma of the title lies in the fact that each prisoner has a choice between only two options, but cannot make the best decision without knowing what the other one will do.

In this hypothetical situation, if both prisoners said nothing, both would receive only 1 year. However, when both inevitably betray the other (for fear that the other prisoner will opt for freedom) they both end up serving a year longer than was necessary.


For Innovative Learning Week, the School of Maths is bringing the Prisoners’ Dilemma back to its roots in game theory. Anyone can attend, but a background and familiarity with Java is a necessary requirement.

Attending this event means you will have the chance to design a computer program to play out the classic Game Theory Prisoners’ Dilemma scenario and see your program fight it out in the grand finale! There will be a lecture to introduce the maths behind the competition, which will be followed by a lab session where you can get started designing your program.

This fantastic event is happening on Monday February 18, 11am – 1pm. There is no booking required, simply turn up at JCMB 5215.

For more information on Innovative Learning Week and the events open to all students, check out the central calendar of events.


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