Self-excitation provides an alternative account of the speed-accuracy trade-off in decision making.

The Speed-Accuracy Trade-off (SAT) is one of the most well-established examples of the adaptability of human decision-making, where faster decisions can come at the expense of accuracy. The threshold-based account, which says that individuals gather less evidence when responding quickly, is widely accepted. Here we propose a fundamentally different mechanism: evidence accumulation becomes more self-excitatory when speed is emphasized. A comprehensive switchboard analysis revealed that self-excitation was the only feature consistently supported across six datasets, whereas adjustments to thresholds, drift rates, or non-decision time received little or no support. We demonstrate that this model better captures key behavioral patterns than the traditional evidence-threshold model. We also present new experimental data which shows that, consistent with a self-excitation model, early evidence is weighted more than late evidence, and that this is especially true when fast responses are encouraged. Overall, our results suggest an exciting new explanation for a long- standing behavioural phenomenon