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Reposted by Yohsuke Murase

Conference on Complex Systems @css-conference.bsky.social · 04/05/2026

Start revving up the engines for #CCS2026! 🚀 Join us Oct 9–16 in Binghamton, NY & online for "Complex Systems for the Changing World."🗺️ Remember to submit by May 15th!📅 Here is our extraordinary keynote lineup spanning networks, life, mind, matter, diseases & society. 🧵👇

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

9/ In short: reputation-based cooperation is sensitive not only to how much information is missing, but to what kind of information is missing. Paper here: www.nature.com/articles/s41...

nature.com

Incomplete reputation information and punishment in indirect reciprocity - Scientific Reports

Scientific Reports - Incomplete reputation information and punishment in indirect reciprocity

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

8/ The broader message is that “imperfect information” is not one thing. Whether punishment helps or hurts depends on what kind of information is missing: unobserved actions, unknown reputations, assessment errors, implementation errors, or perception errors.

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

7/ We then introduced costly punishment as a third possible action, alongside cooperation and defection. In the reputation fading model, norms with punishment can sustain cooperation across a broader parameter range without reducing efficiency.

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

6/ Reputation fading is different. When reputations are sometimes unknown, it becomes harder to identify free-riders, and cooperation requires a higher benefit-to-cost ratio to remain evolutionarily stable.

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

5/ These two cases sound similar, but they lead to qualitatively different outcomes. Under incomplete observation, the condition for cooperation does not change: less frequent reputation updates are exactly offset by stronger reputational incentives.

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

4/ We compared two forms of information limitation. First, incomplete observation: actions are observed only with some probability. Second, reputation fading: a recipient’s reputation is sometimes unavailable and treated as “Unknown.”

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

3/ But reputation systems depend on information. In large or anonymous societies, we may not observe every action, and we may not always know someone’s reputation. How does cooperation survive under such incomplete information?

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

2/ The paper studies indirect reciprocity: cooperation supported by reputation. Instead of helping someone because they helped you directly, individuals help others because they have a good reputation.

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Yohsuke Murase @yohm.bsky.social · 26/04/2026

Our new paper is out! We study how cooperation based on reputation survives when reputation information is incomplete. A key result: “not observing actions” and “not knowing reputations” have very different effects, and costly punishment can help in the latter case. www.nature.com/articles/s41...

nature.com

Incomplete reputation information and punishment in indirect reciprocity - Scientific Reports

Scientific Reports - Incomplete reputation information and punishment in indirect reciprocity

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Reposted by Yohsuke Murase

ICSD2026 @icsd2026.bsky.social · 19/11/2025

Abstract submission for #ICSD2026 is now OPEN!! Submit by December 22, 2025, 23:59 JST (14:59 UTC). Please visit our website for more details: sites.google.com/view/icsd202... *Registration and hotel reservations will be open in February 2026.

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Reposted by Yohsuke Murase

Nikoleta Glynatsi @nikoletaglyn.bsky.social · 03/11/2025

🗞️📣 New paper "Exact conditions for evolutionary stability in indirect reciprocity under noise" with @chilbe.bsky.social & @yohm.bsky.social How can cooperation persist in large groups of unrelated individuals? Reputation 🗣️ But which social norms make this stable, even when mistakes happen? 🧵(1/6)

journals.plos.org

Exact conditions for evolutionary stability in indirect reciprocity under noise

Author summary Understanding how cooperation can evolve and be sustained is a central question in evolutionary biology and social science. One prominent explanation is indirect reciprocity, where indi...

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Yohsuke Murase @yohm.bsky.social · 22/09/2025

This is awesome! Very natural and engaging.

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Yohsuke Murase @yohm.bsky.social · 12/09/2025

The call is closed. We appreciate a lot of applications. Thank you!

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Yohsuke Murase @yohm.bsky.social · 21/05/2025

📢 We’re hiring! RIKEN iTHEMS has launched a new Mathematical Social Science Team, and we’re looking for researchers to join us. If you're into cooperation, norms, or networks, check out the call! 🔗 www.riken.jp/en/careers/r... Feel free to DM me if you have questions!

riken.jp

Seeking a few Research Scientists or Postdoctoral Researchers at Mathematical Social Science Team (W25015)

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Yohsuke Murase @yohm.bsky.social · 13/03/2025

I updated the rb_call library, which allows you to call Ruby methods from Python code. It now works with the latest version of Python. github.com/yohm/rb_call

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Reposted by Yohsuke Murase

Nikoleta Glynatsi @nikoletaglyn.bsky.social · 21/01/2025

A great summary of our recent articles, now live here 👇 The work was conducted at the MPI for Evolutionary Biology🧑🏻‍🔬 Check it out to learn more about game theory and cooperation 🤝

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Yohsuke Murase @yohm.bsky.social · 21/01/2025

This suggests punishment plays a bigger role in indirect reciprocity than previously thought, especially in noisy environments where deception is common. Please check out our paper for more details. sciencedirect.com/science/arti...

sciencedirect.com

Costly punishment sustains indirect reciprocity under low defection detectability

Cooperation is fundamental to human societies, and indirect reciprocity, where individuals cooperate to build a positive reputation for future benefit…

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Yohsuke Murase @yohm.bsky.social · 21/01/2025

Free riders naturally try to hide defection, making detection harder. Our analysis shows that in such cases, punishment is the most efficient evolutionarily stable strategy (ESS) to maintain cooperation.

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Yohsuke Murase @yohm.bsky.social · 21/01/2025

Our study challenges this by showing that costly punishment can be highly effective when detecting free riders is difficult. If defectors can disguise their actions, punishment becomes the best strategy to sustain cooperation.

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Yohsuke Murase @yohm.bsky.social · 21/01/2025

When reputation assessment is prone to errors, punishment can suppress free riders. But the earlier studies argued that frequent punishment lowers overall payoffs, making it less effective than ALLD. Its usefulness was thought to be very limited.

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Yohsuke Murase @yohm.bsky.social · 21/01/2025

For instance, Ohtsuki et al. (Nature, 2009) found punishment ineffective in indirect reciprocity. When reputations are accurately assessed, simply refusing to cooperate deters free riders—costly punishment isn't needed.

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Yohsuke Murase @yohm.bsky.social · 21/01/2025

Does costly punishment—paying a cost to reduce an opponent's payoff—help sustain cooperation in indirect reciprocity? Punishment is often seen as a powerful tool, but its effectiveness here is debated. Our new study explores this: sciencedirect.com/science/arti... 🧵

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