Got mauled by a dog when I was 3. Panic and fear locked my voice away so the brain formed a new neutral path for speech generation. It might have saved me then, but now I'm probably stuck with it forever. William Parry has a convincing explanation for this phenomenon, as MRI scans show that when stuttering, PWS generate speech in regions close to our reptilian brain instead of the prefrontal cortex, where all people, including us, do when speaking fluently. Problem is that because this alternative speech generation path resides in the "deeper" areas of the brain, it is more reactive and gets defaulted to as soon as we get stressed, scared or excited, because the fight or fight mechanism actively shuts down all the higher brain functions. That's why for example, many violence victims report that they can't even talk or scream, they lack the speech generation function in the emergency mode altogether. We however, either genetically or through trauma, have that ability, and because of social anxiety aquired from bad experiences we actively reinforce those neural paths every day. It's a negative feedback loop that is really hard to get out from.