Pool-punishment beats peer-punishment in the evolution of cooperation

Laxenburg, Austria – 14 July 2010.

Scientists have shown that self-governing institutions that promote increased cooperation through a system of punishment can emerge spontaneously, without the need for intervention from a higher authority.

Published in today’s issue of Nature (July 14), an international team of scientists from Austria, Germany, and Canada have demonstrated how and why primitive societies may have evolved from peer-punishment to pool-punishment. In social-learning models called ‘public good games’, peer-punishers take the law into their own hands by penalizing free-riders (those people who benefit from the sanctions but don’t contribute to them), while pool-punishers invest an up-front cost into a social institution issuing sanctions on behalf of the investors.

Peer-punishment maintains cooperation, however, it also incurs a cost to the punisher, who may thus be seen as altruistic. As all players, free-riders included, benefit from the increase in cooperation due to the sanctions, whereas the costs of the sanctions are borne by just a few, punishment systems can become unstable, as punishers grow increasingly dissatisfied with this inequity.

“Sanctions are necessary in modern societies to maintain order and therefore stability,” says lead author Dr Karl Sigmund from the International Institute for Applied Systems Analysis (IIASA) and the University of Vienna.

“Our models suggest that ‘pool-punishment’, where all players are required to contribute to the cost of cooperation, such as paying taxes for a police force, is the most stable form of governance. While peer-punishment can be more efficient, as it only costs if and when someone ‘breaks the law’, it is ultimately problematic, as it is less stable against those taking a free ride on the sanctions imposed by others.”

The study demonstrates that pool-punishment is superior to peer-punishment when dealing with such free-riders. What is more, if everyone cooperates on pool-punishment, the need for peer-punishment will disappear over time. This prediction agrees well with empirical findings by Elinor Ostrom and other social scientists, and advances a specific hypothesis that can be tested experimentally.

Reference: Sigmund K., De Silva H., Traulsen A. & Hauert C. Social learning promotes institutions for governing the commons. Nature 0.1038/nature09203

Author details:
Karl Sigmund: International Institute for Applied Systems Analysis & University of Vienna, Austria.
Hannelore De Silva: Vienna University of Economics and Business, Austria.
Arne Traulsen: Max Planck Institute for Evolutionary Biology, Germany.
Christoph Hauert: University of British Columbia, Vancouver, Canada.

For more information or interviews contact:
Karl Sigmund: IIASA & University of Vienna, Austria, Tel: +43 1 4277 50612; karl.sigmund@univie.ac.at
Leane Regan: IIASA, Tel: +43 2236 807 316, Mob: +43 664 443 0368; regan@iiasa.ac.at

About IIASA:
IIASA is an international scientific institute that conducts research into the critical issues of global environmental, economic, technological, and social change that we face in the twenty-first century. Our findings provide valuable options to policy makers to shape the future of our changing world.

IIASA is independent and funded by scientific institutions in Africa, the Americas, Asia and Europe. www.iiasa.ac.at

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Last updated: 15 Jul 2010