Table 1.

Free parameters for each accumulator model

Parameter	pDDM	cbDDM	usDDM	hpfDDM	Definition
σ	○	○	○	○	Diffusion noise
η	○	○	○		Sensory noise
τ				○	Leak time constant
μ	○	○	○	○	Sensory bias
z0	○	○	○	○	Mean decision bias
z	○	○	○	○	Decision bias range
λ∞			○		Maximum urgency signal
τA			○		Urgency signal time constant
a	△	△	△	△	Decision bound
τa		△			Decision bound time constant
Total no. of parameters	5	5	7	5	Unbounded models
	6	7	8	6	Bounded models

○, Parameters in both unbounded and bounded models; △, parameters in only the bounded models.