PASTIS: A program for curve and distribution analyses

Reaction time (RT) data afford different types of analyses. One type of analysis, called “curve analysis,” can be used to characterize the evolution of performance at different moments over the course of learning. By contrast, distribution analysis aims at characterizing the spread of RTs at a specific moment. Techniques to deduce free parameters are described for both types of analyses, given an a priori choice of the curve or distribution one wants to fit, along with statistical tests of significance for distribution analysis: The log likelihood technique is used if the probability density function is given; otherwise, a root-mean-square-deviation minimization technique is used. A program—PASTIS—that searches for the optimal parameters of the following curves is presented: power law, exponential, and e-based exponential. PASTIS also searches for Weibull and the ex-Gaussian distributions. Some tests of the software are presented.