the only reason to ever cooperate would be if you expect other players who don’t understand game theory to be more likely to cooperate with you if your reputation is greater than 0.
If there are only two kinds of players, those who slack all the time, and those who cooperate on the first round, and then only with anybody with a positive reputation—than the second group will blow the first out of the water. Saying that the winners “don’t understand game theory” sounds a bit silly.
If there is a third kind of player, which cooperates on the first round and then slacks thereafter, then the third group will blow the second out of the water. The second group only wins because no one bothered exploiting them in your example, even though anyone easily could have.
Sure, but then you can add a fourth kind of player, who hunts with those with reputation equal or higher than themselves, it probably beats all three others (though the outcome might depend on the initial mix, if there are more 2 than 4, 3 might exploit enough 2 to beat 4).
And then other strategies can beat that. There are plenty of “nice” strategies that are less foolish than “always slack”.
Good call, I was pretty sure that there weren’t any Nash equilibria other than constant slacking, but everyone using group 4′s strategy is also a Nash equilibrium, as is everyone hunting with those with reputation is exactly equal to their own. This makes group 4 considerably harder to exploit, although it is possible in most likely distributions of players if you know it well enough. As you say, group 4 is less foolish than the slackers if there are enough of them. I still think that in practice, strategies that could be part of a Nash equilibrium won’t win, because their success relies on having many identical copies of them.
If there are two kinds of players, those who throw rock, and those who throw paper, the latter will blow the former out of the the water.
You are engaging in two fallacies: you are cherry-picking conditions to favor your particular strategy, and you are evaluating the strategies at the wrong level. Strategies should be evaluated with respect to how the affect the success of the individual person employing them, not on how they affect the success of people, in general, who employ them. This fallacy is behind much of the cooperate/one-box arguments. Sure, if everyone in Group B cooperates with other members of Group B, then Group B will do better, and on a superficial level, it seems like this means “If you’re in Group B, you should cooperate with other members of Group B”, but that’s fallacious reasoning. It’s the sort of thing that lies behind identity politics. “If Americans buy American, then Americans will do better, and you’re an American, so you will benefit from buying American”. Even if we grant that buying American gives a net benefit to America (which is a rather flimsy premise to begin with), it doesn’t follow that any American has a rational reason to buy American. In your scenario, the presence of people with the “cooperate with people who have a reputation greater than 0” provides a reason to cooperate in the first round, but there is no reason whatsoever to condition cooperation on someone having a reputation greater than 0. Anyone who, in this scenario, thinks that one should cooperate with people with reputation greater than 0 does indeed not understand game theory.
You are engaging in two fallacies: you are cherry-picking conditions to favor your particular strategy, and you are evaluating the strategies at the wrong level.
No, I’m simplifying for arguments’ sake, using the example given by Alex (cooperating with any positive reputation). I discuss more complex strategies elsewhere in the thread, of course “cooperate only with people with > 0 reputation is a pretty stupid and exploitable strategy, my point is that even such a stupid strategy could beat Alex’s “always defect”.
If there are only two kinds of players, those who slack all the time, and those who cooperate on the first round, and then only with anybody with a positive reputation—than the second group will blow the first out of the water. Saying that the winners “don’t understand game theory” sounds a bit silly.
If there is a third kind of player, which cooperates on the first round and then slacks thereafter, then the third group will blow the second out of the water. The second group only wins because no one bothered exploiting them in your example, even though anyone easily could have.
Sure, but then you can add a fourth kind of player, who hunts with those with reputation equal or higher than themselves, it probably beats all three others (though the outcome might depend on the initial mix, if there are more 2 than 4, 3 might exploit enough 2 to beat 4).
And then other strategies can beat that. There are plenty of “nice” strategies that are less foolish than “always slack”.
Good call, I was pretty sure that there weren’t any Nash equilibria other than constant slacking, but everyone using group 4′s strategy is also a Nash equilibrium, as is everyone hunting with those with reputation is exactly equal to their own. This makes group 4 considerably harder to exploit, although it is possible in most likely distributions of players if you know it well enough. As you say, group 4 is less foolish than the slackers if there are enough of them. I still think that in practice, strategies that could be part of a Nash equilibrium won’t win, because their success relies on having many identical copies of them.
If there are two kinds of players, those who throw rock, and those who throw paper, the latter will blow the former out of the the water.
You are engaging in two fallacies: you are cherry-picking conditions to favor your particular strategy, and you are evaluating the strategies at the wrong level. Strategies should be evaluated with respect to how the affect the success of the individual person employing them, not on how they affect the success of people, in general, who employ them. This fallacy is behind much of the cooperate/one-box arguments. Sure, if everyone in Group B cooperates with other members of Group B, then Group B will do better, and on a superficial level, it seems like this means “If you’re in Group B, you should cooperate with other members of Group B”, but that’s fallacious reasoning. It’s the sort of thing that lies behind identity politics. “If Americans buy American, then Americans will do better, and you’re an American, so you will benefit from buying American”. Even if we grant that buying American gives a net benefit to America (which is a rather flimsy premise to begin with), it doesn’t follow that any American has a rational reason to buy American. In your scenario, the presence of people with the “cooperate with people who have a reputation greater than 0” provides a reason to cooperate in the first round, but there is no reason whatsoever to condition cooperation on someone having a reputation greater than 0. Anyone who, in this scenario, thinks that one should cooperate with people with reputation greater than 0 does indeed not understand game theory.
No, I’m simplifying for arguments’ sake, using the example given by Alex (cooperating with any positive reputation). I discuss more complex strategies elsewhere in the thread, of course “cooperate only with people with > 0 reputation is a pretty stupid and exploitable strategy, my point is that even such a stupid strategy could beat Alex’s “always defect”.