A kin-selection model of fairness in heterogeneous populations

Area of Science:

• Evolutionary biology
• Behavioral economics
• Game theory

Background:

• Pro-social preferences for fairness are observed in humans and primates.
• Strong reciprocity is a leading theory for fairness, but overlooks individual differences in heterogeneous populations.

Purpose of the Study:

• To explore the evolution of fairness in heterogeneous populations using kin selection theory.
• To analyze the Ultimatum Game with status-determined roles and non-random pairing.

Main Methods:

• Developed a kin-selection model for the Ultimatum Game.
• Incorporated status-determined roles and non-random player pairing.
• Analyzed conditional and unconditional fairness strategies.

Main Results:

• Fairness can be altruistic or spiteful when behavior is conditioned on game role.
• Altruistic fairness benefits high-value members within a genetic lineage.
• Spiteful fairness disadvantages competitors of an actor's relatives.
• Unconditional fairness can be altruistic (benefiting lineage) or selfish (improving individual standing).

Conclusions:

• Kin selection provides a framework for understanding fairness beyond strong reciprocity.
• Fairness can evolve through various motivations, including altruism and spite, within kin groups.
• The study expands kin-selection explanations for fairness to include motivations beyond spite.