What causes people with tourette syndrome to shout out?

Tics: Patients with tourette have uncontrolled motor movements. When this involves the diaphram and chest it can cause barking, grunting, and expression of words. Often other motor behaviors are also occurring with head, face, throat, and neck involvement. This can be very disruptive and embarrassing. However, many learn to control and manage this even without the need for medication.

Neurologic vocal tic: The answers above are precise and to the point. Many times, the tics slow down with age, but are quite troublesome in school age. The students and teachers need in-service education to understand tourette's and minimize classroom stress on the patient which may exacerbate the tics.