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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

This was a wonderful collaboration with Mark P. Lynch, @molinajohnj.bsky.social, Ryoichi Yamamoto, and Matthew S. Turner.    English Press Release: warwick.ac.uk/news/pressre...  Japanese Press Release: www.iis.u-tokyo.ac.jp/ja/news/5012/

warwick.ac.uk

You don’t need to be a saint to self-isolate

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

This result holds even when a moderate fraction of the population is either asymptomatic or so selfish that they would never adjust their behaviour when sick.

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

For people and policymakers it is important to know under what circumstances Indefinite Suppression is possible. We find that even individuals who care about themselves 100,000 times more than other individuals can decide to aim for Indefinite Suppression.

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

Indefinite Suppression results in far lower costs than Herd Immunity. To our surprise, both equilibria coexist across a vast range of altruism, and it becomes possible to choose Indefinite Suppression even if individuals care about themselves much more than others.

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

In the other equilibrium, individuals who are infectious spontaneously isolate themselves strongly, thereby leading to Indefinite Suppression of the disease. Because the number of infections at any given time stays low, susceptibles can largely go about their lives undisturbed.

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

One equilibrium is selfish in nature, with individuals moderately social distancing only when still susceptible to the disease. The population eventually ends up reaching Herd Immunity. This tends to be very costly.

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

Depending on how altruistic people are, i.e. how much they care for others, there are up to two Nash equilibria. In a Nash equilibrium, it makes no sense for individuals to deviate from what the rest of the population is doing.

3d plot showing the utilities of two Nash equilibria.

One equilibrium is selfish in nature, with individuals moderately social distancing only when still susceptible to the disease. The population eventually ends up reaching Herd Immunity. This tends to be very costly.

In the other equilibrium, individuals who are infectious spontaneously isolate themselves strongly, thereby leading to Indefinite Suppression of the disease. Because the number of infections at any given time stays low, susceptibles can largely go about their lives undisturbed.

Indefinite Suppression results in far lower costs than Herd Immunity. To our surprise, both equilibria coexist across a vast range of altruism, and it becomes possible to choose Indefinite Suppression even if individuals care about themselves much more than others.

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

We studied social behaviour during an epidemic as a self-organised collective phenomenon: People change their behaviour based on their preferences and the epidemic state, which is itself affected by their collective behaviour.

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Simon Schnyder @skschnyder.bsky.social · 30/03/2026

Imagine an epidemic has just appeared on the scene, say, bird flu! You are trying to decide how best to react. If you care for others, how should this affect your behaviour? We addressed this question in a recent paper @PNAS. www.pnas.org/doi/10.1073/...

pnas.org

The theory of epidemics with altruism | PNAS

Social distancing can mitigate the spread of diseases in humans and animals. Social distancing allows susceptible individuals to protect themselves...

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Reposted by Simon Schnyder

arxiv econ.TH @arxiv-econ-th.bsky.social · 08/07/2024

Simon K. Schnyder, John J. Molina, Ryoichi Yamamoto, Matthew S. Turner Nash epidemics arxiv.org/abs/2407.04366

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Reposted by Simon Schnyder

arxiv econ.TH @arxiv-econ-th.bsky.social · 08/04/2024

Simon K. Schnyder, John J. Molina, Ryoichi Yamamoto, Matthew S. Turner Rational social distancing in epidemics with uncertain vaccination timing arxiv.org/abs/2305.13618

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Reposted by Simon Schnyder

arxiv econ.TH @arxiv-econ-th.bsky.social · 08/04/2024

Simon K. Schnyder, John J. Molina, Ryoichi Yamamoto, Matthew S. Turner Rational social distancing policy during epidemics with limited healthcare capacity arxiv.org/abs/2205.00684

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Reposted by Simon Schnyder

Simone Pigolotti @simonepigolotti.bsky.social · 26/05/2025

Our paper on hyperdisordered packing is out! Chromatophore arrangement on squid skin reveals an exotic form of disordered packing, caused by the interplay of cell insertion and surface growth journals.aps.org/prx/abstract...

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Simon Schnyder @skschnyder.bsky.social · 12/03/2025

What’s neat is that we can distill rational behavior down to a simple formula: the strength of social distancing is proportional to both the perceived infection cost and prevalence. Remarkably, this gives a posteriori justification for simple heuristics developed to understand diseases like HIV.

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Simon Schnyder @skschnyder.bsky.social · 12/03/2025

Usually, such Nash equilibria can only be studied numerically, but we found an exact analytic solution for the self-organized social distancing behavior and the corresponding disease dynamics.

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Simon Schnyder @skschnyder.bsky.social · 12/03/2025

Social behavior during epidemics is a self-organized collective phenomenon: People change their behavior based on the epidemic state, which is itself affected by the behavior. Game theoretic analysis shows that such dynamics can give rise to Nash equilibria.

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Simon Schnyder @skschnyder.bsky.social · 12/03/2025

Very happy that our new paper on social distancing during epidemics has just come out in @pnas.org! With @molinajohnj.bsky.social, Ryoichi Yamamoto, and Matthew S. Turner. Understanding Nash epidemics | PNAS www.pnas.org/doi/10.1073/...

pnas.org

PNAS

Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans...

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Simon Schnyder @skschnyder.bsky.social · 04/03/2025

It’s such a pleasure to have you. We hope you’re having a great time!

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Simon Schnyder @skschnyder.bsky.social · 23/01/2025

Hey Saverio, thanks for making this. Can I still be added? Thanks!

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