"According to a controversial new theory, our emotions have evolved as tools to manipulate others into cooperating with us." The New Scientists reports on a new study that says emotions such as anger and gratitude are less about reacting to immediate circumstances and more about negotiating commitment levels in our relationships: "You get angry not when someone hurts you, but when their actions betray a setting of their cooperation dial that is lower than you expect, and your anger is both a threat to turn down your own dial and an inducement to them to turn theirs up."