The presenter was careful to add the disclaimer that it might not be true for everyone. Genetics can have something to do with it, but the stigma some parents put on their stuttering children can and probably definitely does have a detrimental effect on them. My stepfather was a total arsehole to me and would get angry at me when I'd stutter after therapy thinking it would work just like that. My daugher had a stutter, a really severe one, for a week. I made sure nobody, I mean absolutely nobody said anthing about it. I was absolutely terrified for her, but because nobody said anything, it went away just like that. She was distraught to the point of tears, being a 3-4 year old not being able to speak despite being chirpy until then. I think there's something to be said for "ignoring" the problem at the beginning of the affliction. The sample size is 2, I know.