article published yes Christian Hilbe author 2FDF8F3C-F248-11E8-B48F-1D18A9856A870000-0001-5116-955X Laura Schmid author 38B437DE-F248-11E8-B48F-1D18A9856A870000-0002-6978-7329 Josef Tkadlec author 3F24CCC8-F248-11E8-B48F-1D18A9856A870000-0002-1097-9684 Krishnendu Chatterjee author 2E5DCA20-F248-11E8-B48F-1D18A9856A870000-0002-4561-241X Martin Nowak author KrCh department Quantitative Graph Games: Theory and Applications project Modern Graph Algorithmic Techniques in Formal Verification project Rigorous Systems Engineering project International IST Postdoc Fellowship Programme project Indirect reciprocity explores how humans act when their reputation is at stake, and which social norms they use to assess the actions of others. A crucial question in indirect reciprocity is which social norms can maintain stable cooperation in a society. Past research has highlighted eight such norms, called “leading-eight” strategies. This past research, however, is based on the assumption that all relevant information about other population members is publicly available and that everyone agrees on who is good or bad. Instead, here we explore the reputation dynamics when information is private and noisy. We show that under these conditions, most leading-eight strategies fail to evolve. Those leading-eight strategies that do evolve are unable to sustain full cooperation.Indirect reciprocity is a mechanism for cooperation based on shared moral systems and individual reputations. It assumes that members of a community routinely observe and assess each other and that they use this information to decide who is good or bad, and who deserves cooperation. When information is transmitted publicly, such that all community members agree on each other’s reputation, previous research has highlighted eight crucial moral systems. These “leading-eight” strategies can maintain cooperation and resist invasion by defectors. However, in real populations individuals often hold their own private views of others. Once two individuals disagree about their opinion of some third party, they may also see its subsequent actions in a different light. Their opinions may further diverge over time. Herein, we explore indirect reciprocity when information transmission is private and noisy. We find that in the presence of perception errors, most leading-eight strategies cease to be stable. Even if a leading-eight strategy evolves, cooperation rates may drop considerably when errors are common. Our research highlights the role of reliable information and synchronized reputations to maintain stable moral systems. National Academy of Sciences2018 eng 30429320 00045135100006310.1073/pnas.1810565115 1154812241-12246 https://research-explorer.ista.ac.at/record/10293 https://ist.ac.at/en/news/no-cooperation-without-open-communication/ C. Hilbe, L. Schmid, J. Tkadlec, K. Chatterjee, and M. Nowak, “Indirect reciprocity with private, noisy, and incomplete information,” <i>PNAS</i>, vol. 115, no. 48. National Academy of Sciences, pp. 12241–12246, 2018. Hilbe, Christian, et al. “Indirect Reciprocity with Private, Noisy, and Incomplete Information.” <i>PNAS</i>, vol. 115, no. 48, National Academy of Sciences, 2018, pp. 12241–46, doi:<a href="https://doi.org/10.1073/pnas.1810565115">10.1073/pnas.1810565115</a>. Hilbe, Christian, Laura Schmid, Josef Tkadlec, Krishnendu Chatterjee, and Martin Nowak. “Indirect Reciprocity with Private, Noisy, and Incomplete Information.” <i>PNAS</i>. National Academy of Sciences, 2018. <a href="https://doi.org/10.1073/pnas.1810565115">https://doi.org/10.1073/pnas.1810565115</a>. Hilbe C, Schmid L, Tkadlec J, Chatterjee K, Nowak M. 2018. Indirect reciprocity with private, noisy, and incomplete information. PNAS. 115(48), 12241–12246. Hilbe, C., Schmid, L., Tkadlec, J., Chatterjee, K., &#38; Nowak, M. (2018). Indirect reciprocity with private, noisy, and incomplete information. <i>PNAS</i>. National Academy of Sciences. <a href="https://doi.org/10.1073/pnas.1810565115">https://doi.org/10.1073/pnas.1810565115</a> Hilbe C, Schmid L, Tkadlec J, Chatterjee K, Nowak M. Indirect reciprocity with private, noisy, and incomplete information. <i>PNAS</i>. 2018;115(48):12241-12246. doi:<a href="https://doi.org/10.1073/pnas.1810565115">10.1073/pnas.1810565115</a> C. Hilbe, L. Schmid, J. Tkadlec, K. Chatterjee, M. Nowak, PNAS 115 (2018) 12241–12246. 22018-12-11T11:44:05Z2026-08-10T22:30:49Z