Yohsuke Murase

ICSD 2026 - Abstract Submission The abstract submission system is now LIVE at: https://amarys-jtb.jp/ICSD2026/ Abstract submission will close on December 22, 2025 January 5, 2026, 23:59 JST (14:59 UTC).

We have extended the abstract submission deadline to January 5th, 2026!!! Enjoy your holiday season😘

sites.google.com/view/icsd202...

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.

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...

🗞️📣 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)

This is awesome! Very natural and engaging.

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

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

📢 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!

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

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 🤝

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…

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...

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.

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.

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.

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.

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... 🧵