Participants will learn and practice a Go/No-Go reaction time task (Garavan, Hester, Murphy, Fassbender, & Kelly, 2006) that measures inhibitory and excitatory aspects of behavioral control. During the task subjects are presented with an alternating series of Xs and Ys in the center of the screen and must press a button every time they see a Go trial (the letter 'Y' or the letter 'X') while inhibiting a response when they are presented with a No-Go trial (any interruption of the X Y alternating stream, e.g., X Y Y).