Comparison of the spatial and non-spatial treatments.

<p>(a) The fraction of players that have chosen to cooperate is decreasing over time, but remains substantial throughout the experiment <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047718#pone.0047718-Traulsen1" target="_blank">[35]</a>. The error bars are the standard deviations of a binomial distribution, , where is the number of samples and is the fraction of cooperation. (b) The distribution of cooperative acts per player. We do not observe unconditional cooperation, and very little unconditional defection (5 out of 240 players in the spatial treatment and 6 out of 160 players in the non spatial treatment). (c) The distributions of cumulative payoffs are peaked with median of 15.4 € for the spatial and 15.0 € for the non spatial treatment. The standard deviation is 2.3 € in both cases. (d) Correlation between the frequency of cooperation on the x-axis and the cumulative payoff on the y-axis. Each point is one player.