Pretty much. It's already been proven that the brains of PWS have distinct differences from the brains of PWDS. Who even knows what causes it. But there is verifiable evidence of physical differences. I'm not exactly qualified to delve as deeply into this as I'd like, but there is research out there with evidence that chemicals in the brains of stutterers are anomalous, not just in the Broca's area (where speech production originates), but also in the regions of the brain that regulate emotion and attention. Could be they're all tied together.