Subjects will complete eight experimental blocks of testing. One block consists of 20 experimental trials, with each trial lasting about 10 seconds. Five pairs of TMS stimuli are given per trial, with pulses delivered in short bursts of one second each. After each block, subjects draw a mark on a line on paper, showing how much attention they are paying, how much fatigue they are experiencing, and how well they think they are executing the tasks. Each TMS session takes up to 3.5 hours.