I think it could be expectation that plays a trick. ​ I do stutter (more) when with my family, but that is also because my family is the worst: the fact that I have a stammer/stutter is taboo, not something that I can talk with my family about. So, they think that I am slow, stupid or even damaged my brain with too many drugs! :o Because my stutter is hidden, but my speech is slow and hesitant. They don't realize that I speak that way because my brain is not wired for speaking. Having a stammer is neurological.