Research on the formal properties of democratic aggregation mechanisms has a long tradition in political science. Recent theoretical developments, however, show that in the discussion of normative contents of democratic decisions, the actual shape of preferences deserves just as much attention. However, our knowledge about the concrete motivations of individual behavior in democratic decisions is incomplete. Using laboratory experiments, this article examines the existence of social preferences in majority decisions. Contrary to earlier experiments of committee decision making, we develop a design that controls for the conditions of communication and the level of information between subjects. This allows us to comparatively test the predictive power of several theories. We find strong evidence that self-interest and fairness motivate human behavior in majority decisions.