Dual N-Back - Scientifically proven memory workout

 

Every session consists of 40 turns. Each turn a square will light up in a 3x3 grid and a letter will be read out loud. Your job is to remember both the letter and the position of the square - and then indicate when the current square or letter is the same as it was N turns ago. As you get better, the number of turns N you have to remember is increased.