The free-rider detection problem: How groups balance fairness and cooperation

Rules guide and restrict behavior in human society. They play a central role in coordinating social life. Yet, rules are sometimes applied categorically and sometimes more flexibly. You exceeded a speed limit? A police officer may care little about your reason—a rule is a rule. You missed the deadline for an essay but provide a compelling explanation? A teacher may give you the benefit of the doubt and extend the deadline. Why are rules sometimes applied rigidly, while in other circumstances they are applied more flexibly? Lie-Panis et al. (1) develop a compelling game-theoretic model to make sense of this, by connecting it to two other central tenets of human societies: cooperation and deception.