Anxiety may have an effect on stuttering. The right side of the body is controlled by the left side of the brain and vice versa. In the right-handed person the left side of the brain is dominant over the right, and as a result the right hand is given preference over the left. In those who are left-handed the right side of the brain is dominant over the left. It is believed that stuttering often develops when the dominance of the leading side of the brain is incomplete, or when a potentially left-handed child is trained to function as a right-hander. We see then that stuttering results when the messages from the brain to the organ of speech are indecisive. This indecision may be further increased by the presence of anxiety. This is shown very clearly by the fact that many quite normal people show a hesitancy in their speaking or even a mild stutter when confronted with the task of speaking in some formal situation which produces anxiety.
On the other hand, some people stutter without showing or feeling much tension or anxiety at all. As a general rule these people who stutter in the absence of anxiety do not gain much help in their speech difficulty by practising relaxing mental exercises. However, the majority of stutterers experience considerable tension when they are speaking, and with them the reduction of the general level of anxiety by relaxing mental exercises is a great help toward establishing a pattern of easy normal speech.