Is there an R implementation of the linear ballistic accumulator model or Ratcliff's diffusion model for measuring response time and accuracy? I am looking for an implementation of the linear ballistic accumulator model or Ratcliff's diffusion model (e.g. in R, MATLAB, or Python).
Here are a few options. I have not tried them yet personally. 

As mentioned below, the rtdists package in R is able to fit both LBA and diffusion models.

Other Options

LBA

Scott Brown has a copy of Donkin et al (2009) on his web page with some code in R, Excel, and WinBUGS for fitting the LBA model:


http://www.newcl.org/publications/DonkinAverellEtAl2009BRM.pdf
http://www.newcl.org/members/chris/fitLBA.zip


There's also the glba package on CRAN by Ingmar Visser.


http://cran.r-project.org/web/packages/glba/index.html


Diffusion model

The Diffussion model is available as a matlab toolbox called (DMAT).

References


Donkin, C., Averell, L., Brown, S.D., &amp; Heathcote, A. (2009) Getting more from accuracy and response time data: Methods for fitting the Linear Ballistic Accumulator model. Behavior Research Methods, 41, 1095-1110. PDF
Vandekerckhove, J., &amp; Tuerlinckx, F. (2008). Diffusion model analysis with MATLAB: A DMAT primer. Behavior Research Methods, 40, 61-72. doi:10.3758/BRM.40.1.61 PDF