Do experts know what is happening in the brain when a person stutters?
Not really. Doctors know that the brain of adults who stutter is different from other adults, in terms of the localization of speech processing. The right side of the brain in people who stutter seems to be more active than in normal speakers. It is as if the person is trying to re-route the signals around a problem on the left side of the brain, which is the side that normal speakers use. But when the moment of stuttering happens, doctors don't know exactly what is going on in the brain that keeps speech from flowing forward.
At what age does stuttering ordinarily develop?
It almost always happens between the ages of 2 and 5-years-old, when kids are learning to talk. There is so much language and speech development going on in the brain at that time, it is almost more than they can handle. It is especially overwhelming if children are very advanced in language, or have too much to say, and want to make sentences longer and talk faster than the actual motor system can handle.
Alternately, if the child has a bit of a delay in language, some of the language processes are slower than others so there is a kind of 'disynchrony'. It shows up when the person speaks and the words don't flow very smoothly.
What causes stuttering?
In a little more than half of the kids who stutter, there is a family history of stuttering. But there are also kids who stutter who do not have a family history. There may be an inherited factor there, but that the other family members never developed the stutter.
In other cases, there is nothing inherited, but difficult birth conditions may make the brain develop a little bit differently, so it would be due to a congenital factor.
