Fig. 5.

Strategy evolvability.We show the utility function U of an agent as a function of his self-interest I_j and the noise level η, where $U_j\equiv I_j\frac{N_{-}}{N}+(1-I_j)E^{\ast }\left(\eta \right)=(1-\frac{3I}{2})E^{\ast }\left(\eta \right)+\frac{I}{2}$. We show results for populations with a 10% of non-naive agents (see Figs. 2A and 2B), that is, for each set of values {I_j, η}, we select the combination {b_j, s_j} whose efficiency E*(η) maximizes U. In the diagram, we also show that the specific combination {b_j, s_j} that maximizes U defines well separated regions of how different strategies can be optimal for different self-interest and noise levels. Significantly, an agent will choose to be partisan if I_j > 2/3, regardless of the value of η.