FIG. 6.

Illustration of the dual diffusion model and the parameters of the model. There are 2 accumulators with decision criteria c_a and c_b, accumulation rates v_a and v_b (v_a + v_b = v_sum), starting points x_a and x_b (a random number x is selected from a uniform distribution with range s_x and lower limit zero, and x_a = x + x_I and x_b = s_x − x + x_I, where x_I is a minimum baseline starting point), and decay rate (− βx). The equation for the update of evidence in accumulator i (dx_i) at the bottom of the page has time steps of size h, set to 1 ms in the fits of the model to the behavioral data. Variability in processing within a trial (Gaussian noise) is normally distributed with SD σ= 1. Across trials, the nondecision components are uniformly distributed with mean T_er and range s_t.