The researchers studied how people make decisions in bargaining situations using a game called the ultimatum game. They found that by allowing players to adjust offers and not just accept or reject them, they could better understand what drives people's choices. By analyzing this data, they were able to predict how people would behave in other similar games. The key takeaway is that rejections in these games can be explained by people's preferences for fairness and their desire for both their own and others' outcomes to be balanced.