Figure 2. Breakdown of total measured capacity according to the degree of the basis function as a function of the parameter ι for ESN and logistic map, and T_s for RD system.

The values of ρ (0.95 for ESN and 2.5 for logistic map) were chosen close to the edge of stability, a region in which the most useful processing often occurs ²⁷. The scale bar indicates the degree of the polynomial. Capacities for polynomials up to degree 9 were measured, but the higher degree contributions are too small to appear in the plots. Note how, when the parameters ι and T_S increase, the systems become increasingly nonlinear. Due to the fact that the hyperbolic tangent is an odd function and the input is unbiased, the capacities for the ESN essentially vanish for even degrees.