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. Author manuscript; available in PMC: 2009 Jun 8.
Published in final edited form as: Psychol Rev. 2009 Jan;116(1):59–83. doi: 10.1037/a0014086

Figure 3.

Figure 3

The top panel shows accumulators for six confidence categories with the amount of evidence accumulated in each at some point in time. The decision criteria for each accumulator are also shown. The equation shows the change in evidence as a function of time, where v is the drift rate, k is the decay rate, x(t) is the position of the accumulator at time t, dt is the size of the time steps, and σ is the within-trial noise. The middle panel shows how six match values map into the amounts of evidence, that is, how they map into drift rates for the diffusion decision process. The black area determines the drift rate for the highest confidence old category. The bottom panel shows how narrow versus wide separations of confidence criteria (the black areas on the left and right distributions) can lead to large versus small drift rates. For the confidence categories, “−−−” is high-confidence new, “+++” is high-confidence old, and the other symbols represent lower confidence responses.