Abstract Cognitive states such as action intentions leave a fingerprint on human behavior by shaping body movements. Movement trajectories thus provide a unique and elegant tool to uncover such hidden cognitive states, and we will sketch how the method of studying continuous trajectories of computer-mouse movements has evolved over the last decade. We will discuss two spotlights to show how the method can be fruitfully employed in different areas of psychological research. The first spotlight comes from the domain of human action control, and demonstrates how basic action intentions – anticipations of to-be-produced consequences of own body movements – are mirrored in trajectory deflections. The second spotlight features the assessment of cognitive conflict during rule violation behavior in clinically relevant samples. These examples underline the promise of employing hand- and mouse-tracking in both basic and applied research. Contact Roland Pfister, University of Würzburg, roland.pfister@psychologie.uni-wuerzburg.de Robert Wirth, University of Würzburg, robert.wirth@uni-wuerzburg.de