This section of the article provides detailed experimental procedures and methods used in the study of costly punishment across human societies. The authors standardized the experimental protocols to ensure uniformity across different sites, including setting the stake at one day's wage (or $100 in the U.S.) and administering the game in the local language. Participants were individually instructed using fixed scripts, examples, and pre-play test questions to ensure understanding. The game was administered in a secure environment, with participants informed of the optional nature of participation and the importance of confidentiality. The experimental setup included the Dictator Game (DG), Ultimatum Game (UG), and Third Party Punishment Game (3PPG). The authors collected economic and demographic data, focusing on income, wealth, and household size, and used regression analyses to examine the predictive capacity of these variables on individuals' willingness to punish. The results showed that a substantial portion of variation in punishment behavior could not be explained by economic and demographic differences, suggesting that cultural and social factors play a significant role. The study also explored the relationship between punishment, fairness, and altruism, finding positive correlations between punishment willingness and altruistic behavior in anonymous interactions.This section of the article provides detailed experimental procedures and methods used in the study of costly punishment across human societies. The authors standardized the experimental protocols to ensure uniformity across different sites, including setting the stake at one day's wage (or $100 in the U.S.) and administering the game in the local language. Participants were individually instructed using fixed scripts, examples, and pre-play test questions to ensure understanding. The game was administered in a secure environment, with participants informed of the optional nature of participation and the importance of confidentiality. The experimental setup included the Dictator Game (DG), Ultimatum Game (UG), and Third Party Punishment Game (3PPG). The authors collected economic and demographic data, focusing on income, wealth, and household size, and used regression analyses to examine the predictive capacity of these variables on individuals' willingness to punish. The results showed that a substantial portion of variation in punishment behavior could not be explained by economic and demographic differences, suggesting that cultural and social factors play a significant role. The study also explored the relationship between punishment, fairness, and altruism, finding positive correlations between punishment willingness and altruistic behavior in anonymous interactions.