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...

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...

Intensive studies on indirect reciprocity have explored rational assessment rules for maintaining cooperation and several have demonstrated the effects of the stern-judging rule. Uchida and Sasaki demonstrated that the stern-judging rule is not suitable for maintaining cooperative regimes in...