In this experiment stimuli consist of eight unit-digit numbers (1,2,3,4,6,7,8,9). The numbers appear at the center of browser window and participants should indicate whether the presented number is odd (1,3,7,9) or even (2,4,6,8), by pressing left or right arrow key with the left or right index finger. After response, the next number appears automatically. The whole experiment contains two blocks, resulting in 160 trials in total. Each block begins with detailed instruction and short practice. Participants are asked to respond as quickly as possible but to be careful to avoid errors. The experiment will take approximately 15 minutes.