I, myself letter count. I never knew how I happened to start counting letters all the time.. I've done it for awhile. I am now 17. I was doing it not too long ago and I stopped and wondered "Is this normal?", so I did research and found this forum.
What I do is count the letters in an word I hear, and if it comes out to an even number or an odd number that is divisible by something (i.e. 15 15/3 = 5) I consider it a "good" word, but when it comes out odd I actually get kind of aggrivated by it... I've never told anybody about my letter counting, so it's nice to get it off my chest.
