Commercials on the importance of training your brain are nearly a daily occurrence nowadays. A world without Sudoku has almost become unthinkable. Not only puzzles like these, but also numerous specific internet exercise-sites and try-at-home packages are devoted to this phenomenon. This merchandise is usually accompanied by slogans saying something like: "improve cognitive ability and prevent the negative outcome of the aging brain". Just as physical exercise improves the shape of your body muscles, cognitive exercise should keep your brain in optimal form.