Humans choose representatives who enforce cooperation in social dilemmas through extortion

Social dilemmas force players to balance between personal and collective gain. In many dilemmas, such as elected governments negotiating climate-change mitigation measures, the decisions are made not by individual players but by their representatives. However, the behaviour of representatives in social dilemmas has not been investigated experimentally. Here inspired by the negotiations for greenhouse-gas emissions reductions, we experimentally study a collective-risk social dilemma that involves representatives deciding on behalf of their fellow group members. Representatives can be re-elected or voted out after each consecutive collective-risk game. Selfish players are preferentially elected and are hence found most frequently in the ‘representatives' treatment. Across all treatments, we identify the selfish players as extortioners. As predicted by our mathematical model, their steadfast strategies enforce cooperation from fair players who finally compensate almost completely the deficit caused by the extortionate co-players. Everybody gains, but the extortionate representatives and their groups gain the most.

Players are consistent in their strategy over consecutive games also in the 18-players 6 3. Instructions for the three treatments (a) 6-players treatment: Welcome to this experiment in which you can earn money! At the start of the experiment, 40 euros will be credited to your account as your personal endowment. In the course of the game you can decide whether money from your endowment will be invested or not. At the end of the game the savings in your account will be paid cash to you. All your decisions are anonymous. To ensure this, the computer assigns a pseudonym to you, visible at the bottom left of the screen. These pseudonyms are names of moons in our solar system (Ananke, Telesto, Despina, Japetus, Kallisto or Metis). For the experiment to be successful you are not allowed to talk to the other participants or make yourself noticeable to them in any way..
You must confirm all information obtained during the course of the game by clicking NEXT.
After reading this text completely, please confirm by clicking NEXT.
In the course of this experiment you will play exactly 10 climate rounds.
In each of these rounds you can invest in an attempt to protect climate and to avoid dangerous climate change. One of the consequences of dangerous climate change will be serious economic loss, which is simulated in this game.
In each round of the game all six players will be asked simultaneously:

"How much do you want to invest in climate protection?"
(possible answers: €0, €2 or €4) When every player has made his decision all six choices are displayed simultaneously on all six laptops. Afterwards all contributions will be credited to an account for climate protection.
Of the money that has eventually been invested in climate protection, we will place an advertisement in your local newspaper. This advert will give general information about 7 simple methods for climate protection -methods that everybody can implement without much effort to protect our climate and to assist in avoiding dangerous climate change. The more money we collect the larger and more conspicuous the advertisement will be. If this promotion is successful, sponsors for international advertising campaigns could be eventually mobilized.
After reading this text completely, please confirm by clicking NEXT.

Professor Jochem Marotzke, Director of the Max-Planck-Institute for
Meteorology in Hamburg will provide expertise about the state of the climate for the advertising copy. He will also give some recommendations on how to abate CO 2emissions and how the climate can be protected: For example, energy can be saved by decreasing ambient room temperature or by the use of public transportation instead of private cars. Furthermore, the increased use of renewable energy sources contributes to greenhouse gas abatement.
After reading this text completely, please confirm by clicking NEXT

Continued: climate round
After each round the decisions of all players are displayed

Example:
Four players have decided to invest into climate protection. Two of them paid €2 and two of them paid €4. In total 12 euros were paid for climate protection and thus credited to the climate 8 account.
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The end of the game
At the end of the game (after exactly 10 rounds) the computer compares the climate account with the threshold amount of €120. This threshold amount has to be reached to avoid dangerous climate change. It is reached if every player pays on average €2 per round for climate protection. In this case €12 per round would be paid into the climate account. If this amount has been assembled in the climate account, each player will obtain whatever is left over in his account. The money will be paid out in cash anonymously under your pseudonym. If the threshold amount has not been assembled in the climate account dangerous climate change occurs with a probability of 90 % (thus in 9 out of 10 cases) followed by serious economic losses. This is the probability of losing the money in your account and no group member receives a payment.
There is a probability of 10% (thus in 1 out of 10 cases) that you will keep the money in your account. The payment will be paid out in cash anonymously under your pseudonym. The computer decides randomly by "throwing a virtual dice" with this probability.
After reading this text completely, please confirm by clicking NEXT.

The experiment will start now
After reading this text completely, please confirm by clicking NEXT. After reading this text completely, please confirm by clicking NEXT.
In the course of this experiment you will play exactly 10 climate rounds.
In each of these rounds you can invest in an attempt to protect climate and to avoid dangerous climate change. One of the consequences of dangerous climate change will be serious economic loss, which is simulated in this game. In each round of the game all 18 players will be asked simultaneously:

"How much do you want to invest in climate protection?"
(Possible answers: 0, 2 or 4 euros) When each player has made his decision all 18 choices are displayed simultaneously on all 18 laptops. Afterwards all contributions will be credited to an account for climate protection.
Of the money that has eventually been invested in climate protection, we will place an advertisement in your local newspaper. This advert will give general information about simple methods for climate protection -methods that everybody can implement without much effort to protect our climate and to assist in avoiding dangerous climate change. The more money we collect the larger and more conspicuous the advertisement will be. If this promotion is successful, sponsors for international advertising campaigns could be eventually mobilized.
After reading this text completely, please confirm by clicking NEXT

Professor Jochem Marotzke, Director of the Max-Planck-Institute for
Meteorology in Hamburg will provide expertise about the state of the climate for the advertisement. He will also give some recommendations on how to abate CO 2 -10 emissions and how the climate can be protected: For example, energy can be saved by decreasing ambient room temperature or by the use of public transportation instead of private cars. Furthermore, the increased use of renewable energy sources contributes to greenhouse gas abatement.
After reading this text completely, please confirm by clicking NEXT

Continued: climate round
After each round the decisions of all players are displayed.

Example with 6 players instead of 18 players for a better overview:
Four players have decided to invest into climate protection. Two of them paid €2 and two of them paid €4.

Yes No No Yes Yes Yes
Change in the player's account -2,00 0,00 0,00 -4,00 -2,00 -4,00 In total 12 euros were paid for climate protection and thus credited to the climate account. In the real game all 18 players and their decisions are displayed.
After reading this text completely, please confirm by clicking NEXT

The end of the game
At the end of each game (after exactly 10 rounds) the computer compares the climate account with the threshold amount of €360. This threshold amount has to be reached to avoid dangerous climate change. It is reached if each player pays on average €6 per round (this means €2 per member of the group of 3) for climate protection. In this case €36 per round would be paid into the climate account. If this amount has been assembled in the climate account, each player will obtain whatever is left over in his account. The money will be paid out in cash anonymously under your pseudonym.
If the threshold amount has not been assembled in the climate account dangerous climate change occurs with a probability of 90 % (thus in 9 out of 10 cases) followed by serious economic losses. This is the probability of losing the money in your account and no group member receives a payment.
There is a probability of 10% (thus in 1 out of 10 cases) that you will keep the money in your account. The payment will be paid out in cash anonymously under your pseudonym. The computer decides randomly by "throwing a virtual dice" with this probability.
After reading this text completely, please confirm by clicking NEXT

The experiment will start now
After reading this text completely, please confirm by clicking NEXT (c) 6 representatives treatment:

Welcome to this experiment in which you can earn money!
At the start of the experiment, 40 euros will be credited to your account as your personal endowment. In the course of the game you or a group member can decide whether money from your endowment will be invested or not. At the end of the game the savings in your account will be paid cash to you. All your decisions are anonymous. To ensure this, the computer assigns a pseudonym to you, visible at the bottom left of the screen. These pseudonyms are names of moons in our solar system (Ananke, Telesto, Despina, Japetus, Kallisto etc.). For the experiment to be successful experiment you are not allowed to talk to the other participants or make yourself noticeable to them in any way. You must confirm all information 12 obtained during the course of the game by clicking NEXT.
After reading this text completely, please confirm by clicking NEXT.
For this experiment, the 18 players are assigned to six groups of 3 players each.
(see group compilation on the sheet on you desk). For the entire duration of the experiment, you belong to the same group of 3. Your group of 3 is the one in which you see your pseudonym. At the beginning one member of each group is determined randomly, acting as the representative of that group. Your representative is playing together with the other 5 representatives a game in which she has at her disposal the money in total of her group of 3 and decides alone whether and how much she invests thereafter in each round (the accounts of all 3 group members are charged equally). So it depends solely on the decisions of your representative if and how much money you get paid after the game. The rules of the game will be explained in detail on the following pages. After the game the next representative of each group of 3 is chosen actively by the 3 group members and the same game is played again by the elected 6 representatives of the groups.
Each player describes in a few sentences how she would represent the interests of her group members. Only her group members can see this information during the election. When seeing the 3 election pledges of her group simultaneously each group member can vote for one of them by clicking the respective button. The player receiving the majority of votes is elected. If no player gets more than one vote, the computer decides randomly.
Each player receives another endowment of € 40.
After the second game, the active selection of the representative is repeated, and the game is played for a third time again, again with 40 euros endowment per person.
After reading this text completely, please confirm by clicking NEXT In each of the 3 games the respective representative of the group of 3 receives as an addition to his endowment a wage of 3 euros. This wage is charged from the current endowment of the other two group members, € 1.50 each.
Now the game is explained in more detail. The 6 representatives are called players.
Please read the following rules carefully. You could be the next randomly determined representative of your group of 3! Please realize that your representative handles the total money of your group of 3 (that is €120 Euros) and not only his own.
After reading this text completely, please confirm by clicking NEXT In the course of this experiment you will play exactly 10 climate rounds.
In each of these rounds you can invest in an attempt to protect the climate and to avoid dangerous climate change. One of the consequences of dangerous climate change will be serious economic loss, which is simulated in this game. In each round of the game all 6 players will be asked simultaneously:

"How much do you want to invest in climate protection?"
(Possible answers: 0, 6 or 12 euros) Only after each player has made his decision all 6 choices are displayed simultaneously on all 18 laptops. Afterwards all contributions will be credited to an account for climate protection.
Of the money that has eventually been invested in climate protection, we will place an advertisement in your local newspaper. This advert will give general information about simple methods for climate protection -methods that everybody can implement without much effort to protect our climate and to assist in avoiding dangerous climate change. The more money we collect the larger and more conspicuous the advertisement will be. If this promotion is successful, sponsors for international advertising campaigns could be eventually mobilized.
After reading this text completely, please confirm by clicking NEXT

Professor Jochem Marotzke, Director of the Max-Planck-Institute for
Meteorology in Hamburg will provide expertise about the state of the climate for the advertisement. He will also give some recommendations on how to reduce CO 2emissions and on how the climate can be protected: For example, energy can be saved by decreasing ambient room temperature or by the use of public transportation instead of private cars. Furthermore, the increased use of 14 renewable energy sources contributes to greenhouse gas abatement.
After reading this text completely, please confirm by clicking NEXT

Continued: climate round
After each round the decisions of all players are displayed.

Example:
Here four players have decided to invest into climate protection. Two of them paid €6 and the other two paid €12.
After reading this text completely, please confirm by clicking NEXT

The end of the game
At the end of each game (after exactly 10 rounds) the computer compares the climate account with the threshold amount of €360. This threshold amount has to be reached to avoid dangerous climate change. It is reached if each player pays on average €6 per round (this means €2 per member of the group of 3) for climate protection. In this case €36 per round would be paid into the climate account. If this amount has been assembled in the climate account, each player will obtain whatever is left over in his account. The money will be paid out in cash anonymously under your pseudonym.
If the threshold amount has not been assembled in the climate account dangerous climate change occurs with a probability of 90 %

15
(thus in 9 out of 10 cases) followed by serious economic losses. This is the probability of losing the money in your account and no group member receives a payment.
There is a probability of 10% (thus in 1 out of 10 cases) that you will keep the money in your account. The payment will be paid out in cash anonymously under your pseudonym. The computer decides randomly by "throwing a virtual dice" with this probability.
After reading this text completely, please confirm by clicking NEXT

The experiment will start now
After reading this text completely, please confirm by clicking NEXT