| EZ2.mrt {EZ2} | R Documentation |
Given a boundary separation, a starting point, and a drift rate, this function computes the mean exit time/exit time variance of a one dimensional diffusion process under constant drift on an interval with absorbing boundaries. Used as a model of information accumulation, it is gives the mean decision time/decision time variance of responses in a speeded two-alternative forced choice (2AFC) response time task, regardless of whether the response is correct or incorrect.
EZ2.mrt(nu, z, a, s = 0.1, Ter) EZ2.vrt(nu, z, a, s = 0.1)
nu |
Drift rate. |
z |
Starting point. |
a |
Boundary separation |
s |
Scaling parameter (Ratcliff's convention is s = 0.1, the default) |
Ter |
Lag (models non-decision time of a response time) |
This model of information accumulation and decision is a simplified version of Ratcliff's diffusion model (1978). It can be used e.g., to compute the mean response times of the correct responses in a lexical decision time, given the drift rate, the bias (start point), and criterion (boundary separation).
EZ2.mrt returns the mean exit/decision time(s)
EZ2.vrt returns the exit/decision time variance(s)
The return value has the attribute "gradient" attached: the gradient with respect to each of the parameters.
Raoul Grasman
Ratcliff. Theory of Memory Retrieval. Psychological review (1978) vol. 85 (2) pp. 59-108
Grasman et al. EZ2: An extension of teh EZ-diffusion model for Response Time and Accuracy. Journal of Mathematical Psychology (2007) submitted
EZ2-package, EZ2.cmrt, EZ2.cvrt
EZ2.mrt( 0.1, 0.08, 0.12, Ter=0.25)
EZ2.vrt( 0.1, 0.08, 0.12)