It’s my understanding that, in a repeated series of PD games, the best strategy in the long run is “tit-for-tat”: cooperate by default, but retaliate with defection whenever someone defects against you, and keep defecting until the original defector returns to cooperation mode. Perhaps the prisoners in this case were generalizing a cooperative default from multiple game-like encounters and treating this particular experiment as just one more of these more general interactions?
Well, to be precise, researchers found tit-for-tat was the best, given the particular set-up. There’s no strategy that is better than every other strategy in every set-up. If everyone has a set choice (either “always defect (AD)” or “always cooperate (AC)”), then the best strategy is AD. If there are enough TFT players, however, they will increase each others’ scores, and the TFT will be more successful than AD. The more iterations there are, the more advantage TFT will give. However, if all of the players are TFT or AC, then AC will be just as good as TFT. If you have an evolutionary situation between AD, AC, and TFT where complexity is punished, “all TFT” isn’t an equilibrium, because you’ll have mutations to AC, which will out-compete TFT due to lower complexity, until there are enough AC that AD becomes viable, at which point TFT will start to have an advantage again. All AD will be an equilibrium, because once you reach that point, AC will be inferior, and an incremental increase in TFT due to mutation will not be able to take hold. If you have all AC, then AD will start to proliferate. If you have AC and AD, but no TFT, then eventually AD will take over.
It’s my understanding that, in a repeated series of PD games, the best strategy in the long run is “tit-for-tat”: cooperate by default, but retaliate with defection whenever someone defects against you, and keep defecting until the original defector returns to cooperation mode. Perhaps the prisoners in this case were generalizing a cooperative default from multiple game-like encounters and treating this particular experiment as just one more of these more general interactions?
Well, to be precise, researchers found tit-for-tat was the best, given the particular set-up. There’s no strategy that is better than every other strategy in every set-up. If everyone has a set choice (either “always defect (AD)” or “always cooperate (AC)”), then the best strategy is AD. If there are enough TFT players, however, they will increase each others’ scores, and the TFT will be more successful than AD. The more iterations there are, the more advantage TFT will give. However, if all of the players are TFT or AC, then AC will be just as good as TFT. If you have an evolutionary situation between AD, AC, and TFT where complexity is punished, “all TFT” isn’t an equilibrium, because you’ll have mutations to AC, which will out-compete TFT due to lower complexity, until there are enough AC that AD becomes viable, at which point TFT will start to have an advantage again. All AD will be an equilibrium, because once you reach that point, AC will be inferior, and an incremental increase in TFT due to mutation will not be able to take hold. If you have all AC, then AD will start to proliferate. If you have AC and AD, but no TFT, then eventually AD will take over.
Thanks for that explanation. The complexity factor hadn’t occurred to me.