Social versus Moral preferences in the Ultimatum Game: A theoretical\n model and an experiment

In the Ultimatum Game (UG) one player, named "proposer", has to decide how to\nallocate a certain amount of money between herself and a "responder". If the\noffer is greater than or equal to the responder's minimum acceptable offer\n(MAO), then the money is split as proposed, otherwise, neither the proposer nor\nthe responder get anything. The UG has intrigued generations of behavioral\nscientists because people in experiments blatantly violate the equilibrium\npredictions that self-interested proposers offer the minimum available non-zero\namount, and self-interested responders accept. Why are these predictions\nviolated? Previous research has mainly focused on the role of social\npreferences. Little is known about the role of general moral preferences for\ndoing the right thing, preferences that have been shown to play a major role in\nother social interactions (e.g., Dictator Game and Prisoner's Dilemma). Here I\ndevelop a theoretical model and an experiment designed to pit social\npreferences against moral preferences. I find that, although people recognize\nthat offering half and rejecting low offers are the morally right things to do,\nmoral preferences have no causal impact on UG behavior. The experimental data\nare indeed well fit by a model according to which: (i) high UG offers are\nmotivated by inequity aversion and, to a lesser extent, self-interest; (ii)\nhigh MAOs are motivated by inequity aversion.\n