I recently attended a discussion of the prisoner’s dilemma, and someone brought up the fact that when you play this on a two-dimensional lattice, you can get situations where tit-for-tatters defend herds of cooperators against defectors. However, when you introduce a small frequency of long-range interactions, this defence breaks down, and defectors start feeding off the cooperators until they have displaced them entirely. In the medium term, you’re left with a world of defectors and tit-for-tatters, who for all intents and purposes act exactly like defectors (because we’re now well into the game and all tfts have played their first rounds against defectors) until tft starts doing well again in the few places where they can play together; since tit for tat is never first to defect, tfts can cooperate and gain in frequency locally.
The exact result obviously depend on the parameters of the game, but just as epidemiologists like to ponder the consequences of long-haul flights, so do those who’ve studied the prisoner’s dilemma.
The reason I am blogging this is because it tangentially relates to something else that happened to me this week. In Yahoo email, I was confronted with the “not spam” button on a legitimate email. I reasoned that if I pressed the button, it would cause similar messages to appear in other people’s inboxes in the current or future (as opposed to their spam boxes). So while I would have paid the cost of pressing a button, everybody else would get a benefit (except myself, because due to Yahoo’s stupid interface, I still had to move the email back into my inbox in a second, manual step). So I’m punished twice for my good deed. It didn’t seem a good bargain, so I just moved the email to my inbox without telling Yahoo that it was not spam. Yahoo should know anyway that I wouldn’t move proper spam to my inbox (maybe if the contents really caused me fits of laughter, I might do it…) But why should I rub other people’s backs on the web, when they have no way of knowing I did it, and probably wouldn’t feel inclined to thank me anyway?! My conclusion is that providers have to make sure that the morally right way is always the easiest way to perform an operation (preferably, the only way), but you may have different thoughts on this. Let’s hear them!