... You call yourself names when you get something wrong, then aplogize
... You ask yourself questions you already know the answer to
... You run around your bedroom looking for your shirt when you're wearing it.
... You think that the actions of cartoon characters make sense
... You start making sound-effects to fit certain situations (my favourite one is "meep")
... You find yourself cussing in a dead language (such as Latin or Ancient Greek)
... Your nightmares feature the Maths homework you were set the night before, even though you've already done it
(The list goes on and on and on and on......)