When you type faster than usual, it forces you to start looking at the words that are coming up ahead. This helps you figure out where to position your fingers in advance. For instance, if you notice that the next four letters can be typed with your left hand, you can prepare your right hand's finger for the fifth letter before you reach it. Research on highly skilled typists has shown that their speed is closely tied to how far they look ahead at upcoming letters while they type. By seeing and thinking about the letters that are coming next, they are able to type faster and make fewer mistakes.