Since prison culture often emphasizes punishment and retribution for not cooperating with fellow prisoners, the fact that they often cooperate is not surprising. My guess is that if one did this with people who had just been convicted of crimes but had not yet been in prison for a long time, one would see less cooperation.

Before reading this article, and based only on its title, I predicted (on PredictionBook, with confidence 80%) that the result would be that prisoners cooperated "surprisingly" often, based both on the phrase "not what you would expect" and based on vague general things I guessed about prison culture. Thanks for the calibration exercise!

The calibration exercise aside, I don't think this is particularly relevant to PD discussions on LessWrong, which I thought were more about "true" PDs (e.g. us vs. aliens, us vs. a paperclip maximizer). The incentives in a PD between humans are not easily deducible from the setup of the experiment alone.

Link to the original article.

So if you want the other party to cooperate, should you attempt to give that party the impression it has been relatively unsuccessful, at least if that party is human?

Maybe you should give the impression that you're both relatively unsuccessful.

So if you want the other party to cooperate, should you attempt to give that party the impression it has been relatively unsuccessful, at least if that party is human?

I don't think so. It seems more likely to me that the common factor between increased defection rate and self-perceived success is more consequentialist thinking. This leads to perceived success via actual success, and to defection via thinking "defection is the dominant strategy, so I'll do that".

Tim Harford has some relevant comments:

What does that tell us – that prisoners take care of each other? Or that they fear reprisals?

Probably not reprisals: they were promised anonymity. It’s really not clear what this result tells us. We knew already that people often co-operate, contradicting the theoretical prediction. We also know, for instance, that economics students co-operate more rarely than non-economists – perhaps because they’ve been socialised to be selfish people, or perhaps because they just understand the dilemma better.

You think the prisoners just didn’t understand the nature of the dilemma?

That’s possible. The students were much better educated and most students had played laboratory games before. Maybe the prisoners co-operated because they were too confused to betray each other.

That seems speculative.

It is speculative, but consider this: the researchers also looked at a variant game in which one player has to decide whether to stay silent or confess, and then the other player decides how to respond. If you play first in this game you would be well-advised to stay silent, because people typically reward you for that. In this sequential game, it was the students, not the prisoners, who were more likely to co-operate with each other by staying silent. So the students were just as co-operative as prisoners but their choice of when to co-operate with each other made more logical sense.