well it depends from person 2 person how much memory we use, i think memory also depends on the environmental factors of a person e.g a person more happy ,more rich, will obviously be relaxed then a person who is economicaly weak and always think about problems round him ,so as a result the guy with relax environment will obviously have good memory as compared to the other one.......... and also it depends on u ,how much u wana use u r brrrrrrain..