The Stag Hunt
The Trust Game’s quieter sibling, from Rousseau. A stag feeds you both for days — but only if you hunt it together. A hare feeds one, and can be caught alone, safely, every time. The problem here is not temptation. It is assurance: will she be there, and does she think you will?
Before you play
Fen is rational and watchful: she hunts the stag only when she is at least 75 per cent sure you will too, because only then is a three-in-four chance at the feast (4) worth a hare in the hand (3). She starts at 50 per cent — a stranger. Sixteen mornings; make of them what you can.
Rousseau told it in 1755, in his Discourse on Inequality: hunters out after a deer, each knowing he must keep his post, until a hare runs within reach of one of them, who goes after it without scruple, and the deer is lost. Here the hare tempts no one. It is merely safe, and the question is whether a stranger will keep her post.
What just happened
Notice the arithmetic of her heart: a morning you showed up moved her a little; one no-show cut her confidence nearly in half. Trust is built in deposits and lost in withdrawals, and the exchange rate is brutal — which you already knew, from being a person.
Both ways of spending a winter are stable. Hunting together, neither of you gains by switching; hunting hares, neither gains by switching alone. Game theorists call the feast payoff-dominant and the hares risk-dominant: the better place to be, and the safer one. Assurance is what carries two strangers from the second to the first.
The prisoner’s dilemma gets the headlines, but most human–machine coordination is a stag hunt: both sides prefer the cooperative outcome and hesitate only because they cannot be sure of each other. The remedy is not punishment but assurance — track records, credible signals, showing up in the snow. That is the working half of bilateral alignment.
More play on the Playground · the sibling game: The Trust Game