Ultimatum game

What it means

The ultimatum game is a two-player economic game in which a proposer offers a division of a fixed sum and a responder either accepts it, in which case both are paid as proposed, or rejects it, in which case both receive nothing. Standard rational-choice theory makes a clear prediction: a self-interested responder should accept any positive offer because something beats nothing, so the proposer should offer the smallest possible amount. Real behavior flatly contradicts this: responders routinely reject offers they regard as unfair — typically anything much below about a quarter to a third of the pot — choosing to forgo money in order to punish a greedy proposer, and proposers, anticipating this, usually offer substantial, often near-equal, shares. The willingness to pay a personal cost to punish unfairness is the central finding, evidence of strong fairness preferences and 'altruistic punishment' that pure self-interest cannot explain. Offers and rejection thresholds vary somewhat across cultures, linking the game to anthropological work on fairness norms. It matters because it is a clean experimental demonstration that fairness and the desire to punish exploitation are real economic forces shaping bargaining, wage-setting, and cooperation.