Fig. 1.

Illustration of the model. A network is defined by the location of springs (in red), connecting the adjacent nodes of a distorted triangular lattice. A network has higher fitness if its response field $|\delta \text{R}{(\sigma )}^r⟩$ (black arrows) to an imposed stimulus $|\delta {\text{R}}^{\mathcal{E}}⟩$ (purple arrows) reproduces a target displacement $|\delta {\text{R}}^{\mathcal{T}}⟩$ (cyan arrows) at a distant site, consisting here of four nodes. The match between the response field and the target displacement (A) is poor for a random configuration ($T_e=\mathrm{\infty }$) and (B) is almost perfect for a system that has evolved by moving springs at $T_e=0.01$. $L=12$ and $z=5.0$.