The prisoner's dilemma, in real life

posted by Sarah Pavis Aug 08, 2013

You might have hear of the prisoner's dilemma, a classic example in game theory showing why individuals might not cooperate. But what you probably don't know is the name comes from a thought experiment. No one had ever actually tested it on real prisoners. Until now. From Max Nisen at Business Insider Australia:

Surprisingly, for the classic version of the game, prisoners were far more cooperative than expected.

Menusch Khadjavi and Andreas Lange put the famous game to the test for the first time ever, putting a group of prisoners in Lower Saxony's primary women's prison, as well as students through both simultaneous and sequential versions of the game.

The payoffs obviously weren't years off sentences, but euros for students, and the equivalent value in coffee or cigarettes for prisoners.

They expected, building off of game theory and behavioural economic research that show humans are more cooperative than the purely rational model that economists traditionally use, that there would be a fair amount of first-mover cooperation, even in the simultaneous simulation where there's no way to react to the other player's decisions.

And even in the sequential game, where you get a higher payoff for betraying a cooperative first mover, a fair amount will still reciprocate.

As for the difference between student and prisoner behaviour, you'd expect that a prison population might be more jaded and distrustful, and therefore more likely to defect.

The results went exactly the other way for the simultaneous game, only 37% of students cooperate. Inmates cooperated 56% of the time.

A great example of the prisoner's dilemma in action can be seen in this clip from the British game show, Golden Balls. If you can get past the ridiculous name of the show, this illustrates the tension between opposing parties very well:

(via @justinwolfers)