Many scholars turn to emotions to understand irrational behavior. We do the opposite: we turn to rationality and game theory to understand people’s emotions. We discuss a striking theory of emotions that began with the game theory of credible threats and promises, then was enriched by...

Research shows that many animal species have morphological and cognitive adaptations for fighting with others to gain resources, but it remains unclear how humans make fighting decisions. Non-human animals often adaptively calibrate fighting behavior to ecological variables such as resource...

Societies have long struggled with contradictions between the ideals of philanthropy and the real motives of philanthropists. Cultural artifacts such as traditional Jewish legal codes and the legend of Saint Nicholas of Myra show that societies especially revere philanthropists who give...

Group conflicts often break out in which individuals have to choose who to support. Having more supporters tends to increase one's chances of success in conflict, so everyone would prefer to have more supporters. But support is scarce, and sometimes conflicts can arise between two people who...

We investigate in an economic experiment how people choose sides in disputes. In an eight-player side-taking game, two disputants at a time fight over an indivisible resource and other group members choose sides. The player with more supporters wins the resource, which is worth real money....

Immanuel Kant, Adam Smith, Charles Darwin, George Williams, and Stephen J. Gould, among others, have pointed out that observing that a certain behavior causes a certain effect does not itself license the inference that the effect was the result of intent or design to bring about that effect....

We propose that moral condemnation functions to guide bystanders to choose the same side as other bystanders in disputes. Humans interact in dense social networks, and this poses a problem for bystanders when conflicts arise: which side, if any, to support. Choosing sides is a difficult...