I don't know how to stop him, but maybe something similar to this happened when Terry was a baby because he actually likes the sound of fingernails on a chalkboard! Drives me NUTS because he does it sometimes, never thinking about how it affects me because it doesn't affect him at all. So maybe if he continues, your baby will grow up immune to the hideous fingernails on a chalkboard sound.

In case you're wondering, I can always get Terry back. He can't stand to see a hair pulled out of a head. I've got no problem pulling hairs out of my head, especially gray ones, so he starts scratching, I start pulling and we gross each other out. What a great couple, eh?