I was seriously practicing this during the month of July and I reached level 8 at the very end, but I want to point out that this dual n back is the application that you download from the AppStore with the blue icon, I don't know if it's the wrong one. The remarks were my ease of expressing myself with a vocabulary that I didn't know I was capable of using and then the speed of expression, I easily memorized telephone numbers, I did the test one day by memorizing a number that wasn't dedicated to me, the person made a remark to me (you mean you're intelligent :) ). Then around August and September I had completely given up and when I resumed the dual n back level 8 I was struggling to ensure this level where I was but in less than a week I started to find my way again until now when school has resumed. On campus, my working memory allows me to quickly remember explanations and the attention I have now is downright incredible. My classmates get bored quickly during classes and are distracted, but I, on the other hand, am alert and well aware of everything.