The Prisoner's Dilemma is a basic part of game theory. Two prisoners are given the choice between informing on the other, or staying silent. They can't communicate with each other. The choices they make determine how many years in prison they both get.
This analogy/brain game is often used to demonstrate the ways that different people can work with or against each other in economic and social situations. Now, for the first time, scientists have done a study based on The Prisoner's Dilemma that used real prisoners. Instead of time off their sentences, they were given the choice of competing or cooperating to earn goodies like coffee and cigarettes.
And here's the surprise: Compared to college students, the prisoners actually cooperated with each other much more often.