--- res: bibo_abstract: - 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.@eng bibo_authorlist: - foaf_Person: foaf_givenName: Manfred foaf_name: Milinski, Manfred foaf_surname: Milinski - foaf_Person: foaf_givenName: Christian foaf_name: Hilbe, Christian foaf_surname: Hilbe foaf_workInfoHomepage: http://www.librecat.org/personId=2FDF8F3C-F248-11E8-B48F-1D18A9856A87 orcid: 0000-0001-5116-955X - foaf_Person: foaf_givenName: Dirk foaf_name: Semmann, Dirk foaf_surname: Semmann - foaf_Person: foaf_givenName: Ralf foaf_name: Sommerfeld, Ralf foaf_surname: Sommerfeld - foaf_Person: foaf_givenName: Jochem foaf_name: Marotzke, Jochem foaf_surname: Marotzke bibo_doi: 10.1038/ncomms10915 bibo_volume: 7 dct_date: 2016^xs_gYear dct_language: eng dct_publisher: Nature Publishing Group@ dct_title: Humans choose representatives who enforce cooperation in social dilemmas through extortion@ ...