ohh I'm a major nail biter. I've tried the nailpolish thing. It did NOT stop me. I'd just spit the nail polish out after. The bitter tasting stuff didn't work either, I was too focused on biting them.

I've noticed that when I'm busy, I don't bite my nails. When I went camping for a week, my nails were long after the trip because I was having too much fun. I find myself biting my nails in math class but leaving them during choir and piano...hmmm odd eh? I guess for me, boredom provokes me.