[SEQ RERUN] The Truly Iterated Prisoner's Dilemma

MinibearRex

Today's post, The Truly Iterated Prisoner's Dilemma was originally published on 04 September 2008. A summary (taken from the LW wiki):

According to classic game theory, if you know how many iterations there are going to be in the iterated prisoner's dilemma, then you shouldn't use tit for tat. Does this really seem right?

Discuss the post here (rather than in the comments to the original post).

This post is part of the Rerunning the Sequences series, where we'll be going through Eliezer Yudkowsky's old posts in order so that people who are interested can (re-)read and discuss them. The previous post was The True Prisoner's Dilemma, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.

Sequence reruns are a community-driven effort. You can participate by re-reading the sequence post, discussing it here, posting the next day's sequence reruns post, or summarizing forthcoming articles on the wiki. Go here for more details, or to have meta discussions about the Rerunning the Sequences series.

Today's post, The Truly Iterated Prisoner's Dilemma was originally published on 04 September 2008. A summary (taken from the LW wiki):

According to classic game theory, if you know how many iterations there are going to be in the iterated prisoner's dilemma, then you shouldn't use tit for tat. Does this really seem right?

If I know this is your strategy, I don't have to be a perfect rationalist to know that I can defect on the first round.

I don't understand what you mean. Do you mean that if you know Clippy plays TFT-nD, you would defect the first round? Because that would be a very irrational thing to do; sacrificing slightly less than 100 million lives in the process.

0Mass_Driver14y

Are there strategies that, if publicly announced, will let a more sophisticated player defect on the first round and get away with it? Sure. There are also slightly better strategies that can be publicly announced without allowing for useful first-round defection. Either way, though, the gains from even shaky cooperation in a 100-round game are on the order of 70 or 80 million lives -- letting those gains slip by because you're worried about losing 1 million lives on the first round is a mistake. There's a tendency to worry about losing face, or, as Andreas puts it, not being defeated. But with real stakes on the table, you should only worry about maximizing points. Your pride isn't worth millions of lives.