. Author manuscript; available in PMC: 2016 Dec 1.

Published in final edited form as: J Exp Psychol Hum Percept Perform. 2015 Aug 31;41(6):1515–1523. doi: 10.1037/a0039653

Table 3.

Parameters of the Diffusion Model

Condition	a	T_er	η	s_z	p₀	s_t	z	v₁₀	v₂₀	v₄₀	v_c^*	χ²
Experiment 1

eye	0.071	0.254	0.258	0.058	.010	0.065	0.038	0.189	0.428	0.641	0.038	120
touch	0.067	0.386	0.211	0.054	.003	0.147	0.031	0.147	0.412	0.755	−0.012	108
key	0.085	0.327	0.237	0.069	.005	0.110	0.040	0.108	0.469	0.761	−0.009	124

Experiment 2

eye fix	0.061	0.251	0.180	0.049	.001	0.047	0.032	0.217	0.437	0.712	0.009	99
eye 0	0.074	0.278	0.187	0.061	.036	0.115	0.038	0.022	0.139	0.343	−0.037	113
eye 500	0.061	0.250	0.232	0.052	.001	0.046	0.030	0.143	0.370	0.511	−0.053	91
touch fix	0.072	0.391	0.309	0.047	.001	0.115	0.034	0.240	0.495	1.114	0.011	64
touch 0	0.074	0.442	0.345	0.062	.001	0.106	0.039	0.083	0.262	0.578	0.050	74
touch 500	0.071	0.412	0.285	0.058	.002	0.103	0.035	0.085	0.447	0.794	−0.032	62

The accumulation of evidence can have some biases (i.e., all drifts can be lower or higher by a constant), this is represented in the model by the parameter v_c; In all behavioral studies there is a proportion of responses that can be considered contaminants (e.g., the subject pressing a key without seeing the stimulus, this is represented in the mode by the parameter p₀)