If there is any link it is probably between stuttering and *perception* of intelligence. There are lots of time when I know I will get stuck on something so I wont say it then a few seconds later think "wow, good thing I didnt say that, it would have been a stupid thing to say" yet if I *know* that the point is important or good then I will power through the block and get the statement out there. I also have developed a large vocabulary due to all the synonyms I have to know to avoid using word I can feel im about to get stuck on. thus my stutter (and probably most stutterer's) raises my ratio of good points to stupid points and causes me to use a wider variety of words, both thing that make people seem smart.