Christoph Kenntemich

• Norms and their enforcement are the life’s blood of large-scale cooperation. Different cultures have landed at different sets of norms that structure their social togetherness, often shaped by cultural evolution within a set of geographical features. With the internet emerging as an increasingly influential medium of communication, a deep understanding of how norms emerge in online forums is increasingly important. This thesis investigates norm-enforcement in online forums, specifically focusing on 1) inter-culturally consistent parallels between offline- and online norm-enforcement patterns, 2) differences in explicit norms as a causal mechanism behind these parallels, and 3) behavioral consequences of online norm-enforcement. I find systematic differences in online norm-enforcement, that correlate with norms on offline norm-enforcement, with countries that are higher in social ostracism showing less active punishment on Reddit (i.e., negative comments and downvoting) and countries that are higher in verbal confrontation showing more negative comments, but less downvoting, as well as less top-down censorship through moderators. Furthermore, I find that the semantic content of the subreddits’ codes of conduct also vary systematically, according to cultural norms on social ostracism and verbal confrontation. Furthermore, in a set of experimental studies, I find a causal impact of codes of conduct on norm-enforcement behavior, underlining the explicit codes of conduct as a likely causal path of intercultural differences in norm-enforcement behavior in online forums. Lastly, I investigate the behavioral consequences of one norm-enforcement behavior – social ostracism. Across different online forums, users show increased attention seeking following contributions that receive less positive attention. Implications of the set of projects, as well as their innovative methodology, are discussed and potential future research is outlined.