Someone can endorse CDT and still recognize that in a situation where agents make decisions over time in response to each other’s decisions (or announcements of their strategies), unconditional defection can be bad. If you’re instead proposing that we should model this as a one-shot Prisoner’s Dilemma
Well, to be more formal and specific, under CDT, the multi-shot Prisoner’s Dilemma stillunravels from the back into defect-defect at every stage as long as certain assumptions are satisfied, such as the number of stages being finite or there being no epsilon-time discounting.[1]
Even when you deal with a potentially infinite-stage game and time-discounting, the Folk theorems make everything very complex because they tend to allow for a very wide variety of Nash equilibria (which means that coordinating on those NEs becomes difficult, such as in the battle of the sexes), and the ability to ensure the stability of a more cooperative strategy often depends on the value of the time-discounting factor and in any case requires credibly signaling that you will punish defectors through grim trigger strategies that often commit you long-term to an entirely adversarial relationship (which is quite risky to do in real life, given uncertainties and the potential need to change strategies in response to changed circumstances).
The upshot is that the game theory of these interactions is made very complicated and multi-faceted (in part due to the uncertainty all the actors face), which makes the “greedy” defect-defect profile much more likely to be the equilibrium that gets chosen.
“defecting is the dominant strategy in the stage-game and, by backward induction, always-defect is the unique subgame-perfect equilibrium strategy of the finitely repeated game.”
Well, to be more formal and specific, under CDT, the multi-shot Prisoner’s Dilemma still unravels from the back into defect-defect at every stage as long as certain assumptions are satisfied, such as the number of stages being finite or there being no epsilon-time discounting.[1]
Even when you deal with a potentially infinite-stage game and time-discounting, the Folk theorems make everything very complex because they tend to allow for a very wide variety of Nash equilibria (which means that coordinating on those NEs becomes difficult, such as in the battle of the sexes), and the ability to ensure the stability of a more cooperative strategy often depends on the value of the time-discounting factor and in any case requires credibly signaling that you will punish defectors through grim trigger strategies that often commit you long-term to an entirely adversarial relationship (which is quite risky to do in real life, given uncertainties and the potential need to change strategies in response to changed circumstances).
The upshot is that the game theory of these interactions is made very complicated and multi-faceted (in part due to the uncertainty all the actors face), which makes the “greedy” defect-defect profile much more likely to be the equilibrium that gets chosen.
“defecting is the dominant strategy in the stage-game and, by backward induction, always-defect is the unique subgame-perfect equilibrium strategy of the finitely repeated game.”