title: Consistent strategy updating in spatial and non-spatial behavioral experiments does not promote cooperation in social networks.
abstract: The presence of costly cooperation between otherwise selfish actors is not trivial. A prominent mechanism that promotes cooperation is spatial population structure. However, recent experiments with human subjects report substantially lower level of cooperation then predicted by theoretical models. We analyze the data of such an experiment in which a total of 400 players play a Prisoner's Dilemma on a 4×4 square lattice in two treatments, either interacting via a fixed square lattice (15 independent groups) or with a population structure changing after each interaction (10 independent groups). We analyze the statistics of individual decisions and infer in which way they can be matched with the typical models of evolutionary game theorists. We find no difference in the strategy updating between the two treatments. However, the strategy updates are distinct from the most popular models which lead to the promotion of cooperation as shown by computer simulations of the strategy updating. This suggests that the promotion of cooperation by population structure is not as straightforward in humans as often envisioned in theoretical models.
authors.affiliation: Grupo Interdisciplinar de Sistemas Complejos (GISC), Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Madrid, Spain. jelenagr@gmail.com
authors.forename: Jelena
authors.initials: J
authors.lastname: Grujić
authors.forename: Torsten
authors.initials: T
authors.lastname: Röhl
authors.forename: Dirk
authors.initials: D
authors.lastname: Semmann
authors.forename: Manfred
authors.initials: M
authors.lastname: Milinski
authors.forename: Arne
authors.initials: A
authors.lastname: Traulsen
mesh_terms: D003198:Computer Simulation; D003299:Cooperative Behavior; D005716:Game Theory; D006801:Humans; D011336:Probability; D012944:Social Support