Altruists and envious people who meet in contests are symbionts. They do better than a population of narrowly rational individuals. If there are only altruists and envious individuals, a particular mixture of altruists and envious individuals is evolutionarily stable.

In recent years a large number of experimental studies have documented the existence of strong reciprocity among humans. Strong reciprocity means that people willingly repay gifts and punish the violation of cooperation and fairness norms even in anonymous one-shot encounters with genetically...

This paper introduces two ideas, emotional state dependent utility components (ESDUCs), and evolutionary perfect Bayesian equilibrium (EPBE). Using a simple extensive form game, we illustrate the efficiency-enhancing role of a powerful ESDUC, the vengeance motive. Incorporating behavioral noise...

This paper presents a formal theory of reciprocity. Reciprocity means that people reward kind actions and punish unkind ones. The theory takes into account that people evaluate the kindness of an action not only by its consequences but also the intention underlying this action. The theory...

Children who can count on support from altruistic parents may not try hard to succeed in the labor market. Moreover, parental altruism makes withdrawal of such support non-credible. To promote work effort, parents may want to instill norms which later cause their children to experience guilt or...

Most economic models are based on the self-interest hypthesis that assumes that all people are exclusively motivated by their material self-interest. In recent years experimental economists have gathered overwhelming evidence that systematically refutes the self-interest hypothesis and suggests...

Democratic countries with substantial inequality and where people believe that success depends on connections and luck induce political support for high tax rates and generous welfare states. Traditional wisdom is that such policies harm the economy, but there is not much evidence that countries...

We develop a model that allows for public goods and status signaling through charitable contributions. This model provides a unified framework in which contributions are driven both by altruism and status signaling. We use this setup to re-examine the conventional practice of rendering a...