Both in the field and in the lab, participants frequently cooperate, despite the fact that the situation can be modelled as a simultaneous, symmetric prisoner’s dilemma. This experiment manipulates the payoff in case both players defect, and explains the degree of cooperation by a combination...

Both in the field and in the lab, participants frequently cooperate, despite the fact that the situation can be modelled as a simultaneous, symmetric prisoner's dilemma. This experiment manipulates the payoff in case both players defect, and explains the degree of cooperation by a combination of...

If two players of a simultaneous symmetric one-shot prisoner's dilemma hold standard prefer-ences, the fact that choosing the cooperative move imposes harm on a passive outsider is imma-terial. Yet if participants hold social preferences, one might think that they are reticent to impose harm on...

Theoretical and empirical studies have generally weighed the effect of peer punishment and pool punishment for sanctioning free riders separately. However, these sanctioning mechanisms often pose a puzzling tradeoff between efficiency and stability in detecting and punishing free riders. Here,...

Social dilemmas are among the most puzzling issues in the biological and social sciences. Extensive theoretical efforts have been made in various realms such as economics, biology, mathematics, and even physics to figure out solution mechanisms to the dilemma in recent decades. Although...

Despite the accumulation of research on indirect reciprocity over the past 30 years and the publication of over 100,000 related papers, there are still many issues to be addressed. Here, we look back on the research that has been done on indirect reciprocity and identify the issues that have...

The strategy method is often used in public goods games to measure an individual's willingness to cooperate depending on the level of cooperation by their groupmates (conditional cooperation). However, while the strategy method is informative, it risks conflating confusion with a desire for fair...

The black box method was developed as an "asocial control" to allow for payoff-based learning while eliminating social responses in repeated public goods games. Players are told they must decide how many virtual coins they want to input into a virtual black box that will provide uncertain...

Indirect reciprocity is one of the major mechanisms driving the evolution of cooperation in human societies. There are two types of indirect reciprocity: upstream and downstream reciprocity. Cooperation in downstream reciprocity follows the pattern ‘You helped someone, and I will help you’,...

Paying it forward" is a behavior in which people help someone else because they were helped in the past. Although experimental evidence exists that indicates that real human beings often "pay-it-forward" even in the face of free-rider risks, the theoretical basis for the evolution of this...