Prisoner’s dilemmas are interesting because cooperation is socially optimal but not sustained by a Nash equilibrium. Cooperation is fragile. It’s a little “doom and gloom.” Are social species destined to be individualistic selfish assholes?

Under certain conditions, a repeated prisoner’s dilemma becomes a stag hunt. Stag hunts are interesting because cooperation is, in fact, sustained by a Nash equilibrium. But it’s not for free: there’s also a suboptimal Nash equilibrium that could be hard to get out of.

But the moral is that there’s incentive to not be an asshole if there’s a high probability of future encounters.