Fig. 9

In the ERG-ERG control (a), we observe the blue branching (τ_A=0.02), with half the trials diffusing fully and the rest barely diffusing, evidenced by the thicker blue line near the middle. Because τ_B is 0.14, the red line is much lower. In (b), a greater proportion of both contagions diffuse fully. Since the RRG layer diffuses faster all things equal, setting τ_B>τ_A means the two contagions diffuse at a similar rate, indicating synergy inhances diffusion when their rates are similar. In (c), since PLG contagions already diffuse slower than ERG’s, the ERG contagion penetrates similarly as the control, while the PLG barely diffuses. Here, α=3.0