Figure 4.

Learning 90° for initially bistable participants. Top: potential landscape, V solid, V₁(λ) dashed; bottom: phase space portrait; middle: bifurcation diagram. With increasing λ, the unstable fixed point around 90° (dashed line) shifts towards anti-phase and near λ = 2 a saddle-node bifurcation occurs, leading to an additional unstable fixed point (dashed) and an attractor (solid) close to the required phase of ψ = 90° (only the upper half of the bifurcation diagram is shown since the part for negative values of ϕ is symmetric).