Why do individuals engage in personally costly, partisan activities that benefit others? If individuals act according to rational self-interest, then partisan activity occurs only when the benefits of that activity exceed its costs. However, laboratory experiments suggest that many people are...

Participants in laboratory games are often willing to alter others' incomes at a cost to themselves and this behaviour has the effect of promoting cooperation. What motivates this action is unclear: punishment and reward aimed at promoting cooperation cannot be distinguished from attempts to...

We conducted an experiment to describe precisely how social learners use information about the distribution of behaviors in a relevant social group. Players chose between two technologies repeatedly. Payoffs were random, but one technology was better in the sense that its expected payoff was...

Small-scale human societies range from foraging bands with a strong egalitarian ethos to more economically stratified agrarian and pastoral societies. We explain this variation in inequality using a dynamic model in which a population's long-run steady-state level of inequality depends on the...