6. Study design The investigators will ask participants to discriminate the motion direction of a random dot kinetogram (type 1 task). They will use a mouse to indicate whether the dots were mostly moving rightward or leftward, by clicking on the side they think corresponds to a correct answer (red and blue circles, see Figure 1). The mouse trajectory corresponding to the type 1 task will be recorded and analyzed. Motion variance will be adapted for each subject before the experiment using a 1up/2down staircase, so to reach an average performance of 71%. An auditory feedback will be played if participants answer in more than 6s. On each trial, participants will then indicate on a visual analog scale the confidence in their response (type 2 task). The scale will range from 0% ("Certain my response is right") to 100% ("Certain my response is wrong"). The initial position of the cursor will always correspond to 50% confidence ("Uncertain of my response)". The experiment will consist in 10 blocks of 30 trials and last about 1h.