I don't know what it is, but somehow being in front of a laptop reduces my cognitive ability significantly :/. I actually take notes on a tablet just so that my notes are all in one place but I kind of wonder if I should go back to paper. It's not even the distraction possibilities I think, though that does happen. I can have some task to do, open up my laptop to do it, and then instantly forget what it was I wanted to do, then go on HN/reddit for a while and then realize I was supposed to be doing something...