Speaking from the experience. You do pick up a stutter. When I was very young, my brother had a stutter. I used to tease him all the time. Whenever he called me broo-oo-th---er, I replied y--y--e--ee-s wht--tt-up? After a month or so, he literally stopped stuttering and guess what. I started to stutter since then. This happened when I was in Grade-1. I am now 24 years old. I still stutter. Life lesson learned. Never make fun of anyone because karma is really a bitch.