According to [this research](https://www.stuttering.co.nz/news/is-stuttering-genetic/): “children who stutter often have a family history of stuttering however the relationship between genetics and stuttering is far from clear. About 70% of those who stutter have a family history of stuttering, so a family history isn’t necessary for stuttering to develop. There are even cases of identical twins, who share the same genetic material, where one twin stutters and the other doesn’t.” Some PWS have a genetic predisposition and some don't. Speaking is a learned behavior, so it's not something we are born with. PWS develop stuttering by anticipating and justifying compulsion, and other primary and secondary behaviors.