Stag Hunts: fascinating and useful game theory model for collective action problems


Yesterday, I wrote about some Johns Hopkins students who overcame a game theory problem and got an A for the whole class. I called it a non-iterated Prisoner's Dilemma, but as Tim Harford points out, it's more of a Stag Hunt, a game theory category that I hadn't been aware of, and which has fascinating implications for lots of domains, including Internet peering:

In the stag hunt, two hunters must each decide whether to hunt the stag together or hunt rabbits alone. Half a stag is better than a brace of rabbits, but the stag will only be brought down with a combined effort. Rabbits, on the other hand, can be hunted by an individual without any trouble.

There are two rational outcomes to the stag hunt: either both hunters hunt the stag as a team, or each hunts rabbits by himself. Each would prefer to co-operate in hunting the stag, but if the other player’s motives or actions are uncertain, the rabbit hunt is a risk-free alternative.

Right on queue

(Image: [ C ] Lucas Cranach - Stag Hunt of the Elector John Frederick, a Creative Commons Attribution (2.0) image from centralasian's photostream)