Why Could I Without Trying??

its like i can slack off for 3 days and on the 4th when im actually doing some work i understand right away, my friends study so hard and i do nothing but watch tv and play computer but i always end up with the highest score on tests/quizes and midterms, even when i say somthing is hard cuz it really is for me i always end up with good grades, why do i do so good in school even when i dont try even as half as hard as my friends, is there a name for this??