Participants will have several 1-hour training sessions. During these sessions, they will sit facing a computer screen at a distance of about 32 inches (80 centimeters) from their eyes. Six permanent position markers will be displayed. A keyboard with six spatially compatible response keys will be within reach of their right hand. Participants will respond as quickly and as accurately as possible to the appearance of a stimulus (e.g., white circle) below one of the markers by pressing the spatially corresponding key. About a second later, the next stimulus will be displayed below one of the other markers, and so on. Reaction times and accuracy will be recorded. After 3 to 10 minutes of practice (one block), there will be a rest period during which the computer will display information about the subject's accuracy of movements and reaction time. Then, a new block will start. There will be about 6 to 20 practice blocks per training session. The number of training session will vary between 3 and 6 depending on accuracy and reaction time during the task.