Former SCL student Jelena Grujic, from Department od Mathematics, University Carlos III, Madrid, Spain, held a seminar talk entitled "Prisoner's dilemma, the experiment".

Abstract of the talk:

Although defection is evolutionarily selected in well‐mixed populations playing Prisoner's Dilemma, theoretical models show that depending on how strategies are updated, cooperation can emerge in spatially or socially structured populations. Here we report onexperiments with human subjects on a large network. The most striking result is that players do not follow a single behavioral pattern: We find a high percentage of pure or almost pure defectors and a sensibly smaller one of pure or almost pure cooperators which cannot cluster. The remaining players are more or less prone to cooperate depending on the amount of cooperators in their neighborhood. This heterogeneity of behavior leads to a low (albeit nonzero) level of cooperation. Theoretical models need to incorporate and hopefully explain this behavioral diversity.