Five-year-olds understand fair as equal in a mini-ultimatum game.

In studies of children's resource distribution, it is almost always the case that "fair" means an equal amount for all. In the mini-ultimatum game, players are confronted with situations in which fair does not always mean equal, and so the recipient of an offer needs to take into account the alternatives the proposer had available to her or him. Because of its forced-choice design, the mini-ultimatum game measures sensitivity to unfair intentions in addition to unfair outcomes. In the current study, we gave a mini-ultimatum game to 5-year-old children, allowing us to determine the nature of fairness sensitivity at a period after false belief awareness is typically passed and before formal schooling begins. The only situation in which responders rejected offers was when the proposer could have made an equal offer. But unlike adults, they did not employ more sophisticated notions of fairness that take into account the choices facing the proposer. Proposers, in their turn, were also not adult-like in that they had a very poor understanding that responders would reject unequal offers when an equal one was available. Thus, preschool children seem to understand "fair=equal" in this task, but not much more, and they are not yet skillful at anticipating what others will find fair beyond 50/50 splits.