This is often happens and makes stammering incredibly frustrating.
Many people who stammer, and these can include children, are aware that some situations are easier than others.
It is often easier to talk to people who are familiar. Particularly if they are used to the stammer and accept it easily. On the other hand, strangers or people who are "important" in some way can make the person feel more anxious about stammering. This leads to greater efforts to avoid or hide it. This increase in tension will in turn increase the likelihood of the stammer occurring.
We all react with increased tension in certain situations, and the result can mean that we don't function quite as well as we would like.
