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.

Altruistic punishment - the punishment of norm violators at one's own cost without material benefit - is frequently observed in experimental economics, field studies and in people's everyday life. The existence of this ostensibly irrational behavior is often linked to other-regarding preferences...

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 a haystack-type representation of a heterogeneous population that is evolving according to a payoff structure of a prisoner's dilemma game, migration is modeled as a process of swapping individuals between heterogeneous groups of constant size after a random allocation fills the haystacks,...

We study the coevolution of cooperation, preferences and cooperative signals in an environment where individuals engage in a signaling-extended prisoner's dilemma. We identify a new type of evolutionary equilibrium - a transitional equilibrium - which is constituted and stabilized by the dynamic...

We propose a simple model for why we have more trust in people who cooperate without calculating the associated costs. Intuitively, by not looking at the payoffs, people indicate that they will not be swayed by high temptations to defect, which makes them more attractive as interaction partners....