A norm knockout method on indirect reciprocity to reveal indispensable norms

Area of Science:

• Evolutionary Game Theory
• Social Dynamics
• Computational Biology

Background:

• Evolutionarily stable strategies for cooperation against free riders are known.
• The dynamics of norm alternation and the role of diverse norms in cooperation remain unclear.
• Understanding these dynamics is crucial for explaining the evolution of cooperation.

Purpose of the Study:

• To clarify the co-evolutionary dynamics of norms and cooperation in indirect reciprocity.
• To identify indispensable norms for the evolution and maintenance of cooperation.
• To investigate the role of norm diversity in establishing cooperation.

Main Methods:

• Development of a 'norm knockout method', inspired by gene knockout techniques.
• Utilizing numerical investigations to simulate norm dynamics and cooperation evolution.
• Analyzing the impact of removing specific norms on cooperative outcomes.

Main Results:

• A transition from strict to tolerant norms was observed after the elimination of defectors.
• Strict norms are essential for the initial establishment of cooperation by removing defectors.
• Eliminating specific intolerant norms prevents the emergence of cooperation.

Conclusions:

• Strict norms are indispensable for initiating cooperation by purging defectors.
• Cooperation evolves through a process where strict norms are eventually replaced by tolerant ones.
• Norm diversity, particularly the presence of intolerant norms, is critical for sustained cooperation.