I have always wondered whether a particular personality type is more susceptible to becoming a person who stutters. Recently I came across the term "Highly Sensitive Person" (HSP). Apparently about 1/5 of the world population are HSPs. They may process sensory data much more deeply and thoroughly due to a biological difference in their nervous systems.
This trait is not only found among humans, but in nearly all higher animals as well as some other animals. For instance, some members of certain ape varieties act as natural 'guards' - warning the others when danger approaches - due to their inherent sensitivity to unfamiliar noises, smells and sights, and even their intuition.
But there is a downside. Not surprisingly, HSPs can suffer from anxiety, particularly social anxiety, because of their highly tuned sensory systems. It's easy to become anxiety-ridden when your "radar" picks up even the most minute risks and threats.
Though most HSPs are introverts, there are also extroverts among them, so it's not an introvert/extrovert thing. Being an HSP should not be seen as negative and something to be "treated"; research shows that being an HSP can be conducive to survival, as a sensitive person is more aware of danger and so can avoid risks better.
A contributory cause?
How does this relate to stuttering? I think it's reasonable to expect that the HSP will be more susceptible to stress and tension. Significantly, a study by Libby Oyler, done for her speech and language pathologist degree, found that while the percentage of highly sensitive people in the general population is 20%, that figure exceeds 80% for people who stutter.
I am, of course, not suggesting that sensitivity is a cause of stuttering. Not all sensitive people stutter. But it seems that it is a CONTRIBUTORY cause.
PLEASE take part in the informal poll below on whether you are an HSP who also stutters! And if you are interested in the subject, do check out the Wikipedia article on HSPs which you will find HERE. A number of books have been written on the subject - you will find links to them in the Wikipedia article.