There is the strange thing that happens to you in an examination hall. You are trying really hard to concentrate on this problem but then instead you start singing a song or that song keeps ringing in your head. It need not be necessary for you to start singing or even humming it but you would be singing it in your head. I remember for my 12th grade finals (a huge thing in India called the boards) I think i was singing mauja hi mauja ( a song from this movie jab we met). Even for my end semester exam in college I found myself humming this ridiculous hindi song darling. Has something like this ever happened to you??