Co-Evolution for Different Dilemmas and Time Scales

<p>Results for the fraction of successful evolutionary runs ending in 100% cooperation for different values of the time-scale ratio <i>W</i>. We study the most popular social dilemmas of cooperation: the prisoner's dilemma (PD) (<i>T ></i> 1 <i>></i> 0 <i>> S</i>), the snowdrift game (SG) (<i>T ></i> 1<i>> S ></i> 0), and the stag-hunt game (SH) (1 <i>> T ></i> 0 <i>> S</i>). For <i>W =</i> 0 (<i>N =</i> 10³, <i>z =</i> 30 and <i>β =</i> 0.005), the results fit the predictions from well-mixed populations. With increasing <i>W</i> the rate at which individuals readjust their ties increases, and so does the viability of cooperation. Above a critical value (<i>W_critical</i> ≈ 4.0, detailed in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.0020140#pcbi-0020140-g003" target="_blank">Figure 3</a>), cooperators efficiently wipe out defectors. According to [<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.0020140#pcbi-0020140-b008" target="_blank">8</a>], only when <i>b/c ></i> 30 would cooperation be favored. Co-evolution leads to full cooperation even when <i>b/c =</i> 2 (<i>T =</i> 2, <i>S =</i> −1).