Certain phenomena are associated with stuttering and are not associated with other communication disorders or with normal fluency. The secondary behaviors accompany the core behaviors and vary from person to person. They are learned behaviors which usually occur in a hierarchy from least noticeable to more and more conspicuous. Tension and tremor are often the first two secondary behaviors to appear. Tension appears first in the lips, tongue, and jaw, and may spread to other parts of the face, head and neck.
Excessive tension can eventually lead to tremors of muscles.
Tremors constitute involuntary muscle movements which can cause a person to feel out of control of that particular muscle or out of control of the ability to speak. Tremors can have a powerful effect on the person who stutters and lead the person to seek any possible way to avoid the tremor in the first place or to escape the tremor and the feeling of loss of control. Behaviors such as using sudden, jerky movements to interrupt the tremor, or pushing the muscles or air harder to release the blocked speech, will occur in attempt to release the tremors. Some clinicians believe that tremors hold the seeds of fear. The tremors and fear, together, lead the person who stutters into a downward spiral involving layers of covering up and avoiding.