Game Theory: Winning doesn't have to jingle

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Game Theory: Winning doesn't have to jingle
Game Theory: Winning doesn't have to jingle

Winning doesn't have to jingle

The global climate can be viewed as a public good. But how can you persuade people to work selflessly to preserve it? Perhaps by not only being well informed, but also by making their good deed public: Praise from all sides can even be worth more to the noble donor than mere Mammon. The exciting field of research between altruism and egoism has long been plowed by psychologists, sociologists and game theorists. Now two German teams of scientists from very different disciplines combined their interests – the Max Planck Institute for Limnology in Plön and the Max Planck Institute for Meteorology in Hamburg – and started a classic game theory experiment. Their goal: climate protection.

In the experiment, four subjects are given an amount of ten euros; in each round, players may pay between zero euros and the entire amount into a common pool without their fellow players finding out the amount. A game master collects the money, adds the same amount and divides the amount equally among all players.

If everyone gives everything they have, they will all get double in return. On the other hand, if only a single player donates something and the others nothing, then he loses half of his stake, while his fellow players were allowed to pocket a profit without the risk of losing their own money. Therefore, nobody usually pays into the pool voluntarily: This is the only way to avoid the high risk of loss.

The Max Planck scientists modified this experiment. They informed the players that their bet would not be paid out after the game but would be doubled and invested in a newspaper ad. In it, the Max Planck Institute for Meteorology would inform the public about the state and the expected development of the global climate and give a list of simple but effective rules how everyone can reduce the emission of carbon dioxide.

The players - a total of 156 Hamburg students - were allowed to decide anonymously or by giving their pseudonyms whether and how much they wanted to donate from their personal budget to the joint ad pool. In between, there were always rounds of another game in which you get something from other players if you have a high "reputation". Each player will be asked if they want to give money to another player. In the positive case, the recipient receives double the donor's stake. Beforehand, the donor and all other players are informed whether and how much the recipient has paid in each non-anonymous climate round and in reputation rounds. In this way, his commitment to climate protection and his rewarding behavior can be rewarded. In addition, every second group of six players received scientific information about the causes and consequences of climate change.

The result surprised the scientists: All players donated money for the ad; Players informed about climate change showed the greatest willingness if they could publicly pay into the climate pool. In the rounds of two, donors gave preference to those recipients who had previously donated to the ad pool. Very little was paid into the climate pool anonymously, i.e. without any gain in reputation. It can therefore pay off to invest in climate protection - through the associated reputation gain: "Do good if others can see it too!" But scientific information also has a significant effect on the willingness to invest publicly or anonymously in climate protection.

The scientists advise politicians to pay more attention to the development of strategies that can be used to publicize investments by fellow citizens in climate protection. © Max Planck Society

The Max Planck Society (MPG) is a basic research institution funded primarily by the federal and state governments. It operates around eighty Max Planck Institutes.

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