MouseTracker: Software for studying real-time mental processing using a computer mouse-tracking method. MouseTracker is a freely available, user-friendly software package that allows researchers to record and analyze hand movements traveling toward potential responses on the screen (via the x, y coordinates of the computer mouse). By looking at the dynamics of how participants’ hand movements settle into a response alternative—and how they may be partially pulled toward other alternatives—researchers glean valuable information about real-time cognitive processing. MouseTracker opens up a single reaction time into a continuous stream of rich cognitive output.