I have done all of these things and still stutter...I've worked jobs where I've had to communicate with multiple people during the day. I worked fast food and to deal with 100+ customers and had to take orders using a headset, sometimes 30,40, 50 per shift. I now work in a call center (which I hate, not because of my stutter, but because of other reasons..) taking 30-40 calls per day. My whole entire job is speaking. My major at school was modern languages, in which I had to take language courses that involved a LOT of speaking, partner work, presentations in front of the class, and even recording ourselves speaking the language for assignments. I took Japanese classes and a Mandarin class in which I had to record myself speaking for assignments. I even entered a Japanese speech contest twice. I even did online tutoring teaching Japanese people English through video chat. I have gone abroad and talked to many people in a foreign language. I have talked to strangers, had to be an impromptu interpreter. I'm definitely not the most outgoing person out there but there's no way I haven't challenged myself with my speech. And I still stutter!! Explain this please? I have no problem talking on the phone, ordering food, talking to strangers etc. Granted, my fluency level is high, but I still stutter. So if your theory is true, then why do I still stutter?