The ultimatum game is one of the most famous experiments in economics. It involves two players, one of them receives a sum of money which he has to share with a second player. The first player, the “proposer”, can decide how much he offers the second player, called “responder”, who can either accept or reject the offer. If the responder rejects, neither of the players receives any money. Mathematically, the first intuition is to offer the opponent the smallest amount possible. However, during the game players routinely reject even high offers if they deem the split unfair. In this video, WERNER GÜTH explains how he came to develop the ultimatum game and how modifications of the game produce different outcomes.