Evidence accumulation: trajectory to decision boundary, RT distributions, speed-accuracy tradeoff
—
mean RT (ms)
—
accuracy %
—
error RT (ms)
0
trials
Accumulator
0.50
0.80
1.20
0.00
dx = v·dt + σ·dW. Decision at ±a. Correct = upper boundary (positive drift). Speed-accuracy tradeoff via threshold.
Timing
200
1.0
5
T_er = non-decision time (encoding+motor). Total RT = decision time + T_er. Shown in distribution plot.
RT Distribution
Correct trials: blue bars. Error trials: red bars (upward). RT distribution is right-skewed (Wald distribution). Speed-accuracy tradeoff: low threshold → fast+inaccurate, high threshold → slow+accurate.