Humans carry out actions either in response to environmental demands, or independently of external input in order to achieve their goals. The first type of action may be referred to as stimulus-based or reactive, the latter kind may be referred to as intention-based or voluntary. Voluntary actions are an important component of our interaction with the environment and our social lives. Yet, research on human action has only relatively recently begun to try to understand the control of voluntary actions, focusing instead on action that is performed in response to a stimulus in the environment. The proposed project will pursue this attempt to elucidate the functional and neurophysiological underpinnings of voluntary actions along several axes (e.g., neural and functional mechanisms of voluntary action control, functional differences between voluntary and stimulus-based action control, mechanisms of action-effect learning). The project will approach these issues with the help of techniques coming from psychophysics (e.g., signal detection theory) and neurophysiology (EEG, fMRI), separately, and also in combination. Its aim is to shed light on yet unexplored issues in research on voluntary action control, such as its cortical mechanisms and time course, and to provide new methods for further sophisticated investigation.