Figure 4. Results from the SBD model. (A) Ten realizations of the SBD with a 20x20 system started at S(0) = 65, which is just above the unstable equilibrium of S₂^*= 64.1 (dashed line). Three realizations go to the lower equilibrium and seven go to the upper equilibrium. (B) The effect of initial conditions and system size on the equilibrium. One thousand simulations were run at each of 100 initial conditions between S(0) = 60 and S(0) = 70 and the proportion that went to the upper equilibrium was computed. This experiment was repeated for three system sizes: (a) 10x10, (b) 20x20, and (c) 30x30. The vertical dashed line locates the unstable equilibrium S₂^*. See Donalson et al. (2003, 604KB) for details.