The primary goal of this chapter is to collect and analyze reaction time data using MATLAB®. Reaction time measures to probe the mind have been the backbone of experimental psychology at least since the time of Donders (1868). The basic premise underlying the use of reaction times in cognitive psychology is the assumption that cognitive operations take a certain and measurable amount of time. In addition, it is assumed that additional mental processes add (more or less) linearly. If this is the case, increased reaction times reflect additional mental processes. Let us assume for the time being that this is a reasonable framework. Then, it is highly useful to have a program that allows you to quickly collect reaction time data.