Why should you help a competitor? Why should you contribute to the public good if free
riders reap the benefits of your generosity? Cooperation in a competitive world is a …

Combining evolutionary models with behavioral experiments can generate powerful insights
into the evolution of human behavior. The emergence of online labor markets such as …

Although adults generally prefer helpful behaviors and those who perform them, there are
situations (in particular, when the target of an action is disliked) in which overt antisocial acts …

Economists and biologists have proposed a distinction between two mechanisms–“strong”
and “weak” reciprocity–that may explain the evolution of human sociality. Weak reciprocity …

A defining aspect of human cooperation is the use of sophisticated indirect reciprocity. We
observe others, talk about others, and act accordingly. We help those who help others, and …

A longstanding idea in the literature on human cooperation is that cooperation should be
reinforced when conditional cooperators are more likely to interact. In the context of social …

Economic experiments have shown that punishment can increase public goods game
contributions over time. However, the effectiveness of punishment is challenged by second …

Cooperation, where one individual incurs a cost to help another, is a fundamental building
block of the natural world and human society. It has been suggested that costly punishment …

Children aged 3 years and 4½ years old watched a puppet, struggling to achieve goals, who
was helped by a 2nd puppet and violently hindered by a 3rd. The children then distributed …

Many interactions in modern human societies are among strangers. Explaining cooperation
in such interactions is challenging. The two most prominent explanations critically depend …