2–6 years old. There are types of dysfluencies that are normal developmental processes and others that are more abnormal and atypical. Stuttering Stuttering is the most common dysfluency disorder. it is an interruption in the flow of speaking characterized by repetitions, sound prolongations, and blocks that change the rhythm of sleep. A disturbance in the normal fluency and time patterning of speech that is inappropriate for the age of the person. Stuttering typically has its origins in childhood. Most who stutter will begin to do so around 2.5 years of age. Approximately 95% of children who stutter will start to do so before the age of 5. Stuttering symptoms may include dysfluencies such as hesitations, word fillers, nonword fillers, silent pauses, and interjections. All very similar to developmental dysfluency symptoms. Less typical stuttering will include sound/syllable repetitions, prolongations, and blocks. Stuttering can also occur with other speech and sound disorders, and intellectual language disabilities. Stuttering can greatly interfere with school, work or social interactions. Children who stutter may also experience fear or anxiety about social settings or public speaking. Speech patterns and behaviors that might signal that a child is potentially going to develop a stuttering disorder can include within-word or part0word repetitions prolonged sounds, avoiding speaking situations, looking frustrated or upset and tense appearance in neck muscles. If stuttering is familial there is likely a genetic mutation that causes the disorder. Unlike the aforementioned typical dysfluencies, stuttering can be a result of genetics. Mutations on the GNPTAB, GNPTG, and NAGPA have been found to disrupt the signal that directs enzymes to target locations in the brain and cause stuttering in vocal and linguistic processes. Cluttering Cluttering (Tachyphemia) is a fluency disorder that can co-occur with stuttering but may also occur individually. When someone is experiencing cluttering disorder their conversation segments may be perceived as too fast, too irregular or both. Other symptoms may include stuttering, language or phonological errors, and attention deficits. It may result from disorganized speech planning or being unsure of what to say. Both cluttering and stuttering are forms of fluency disorders that develop beyond the key years of about ages 2–6. During these ages, dysfluency is mainly just considered to be developmental dysfluency. Cluttering, unlike stuttering, can be distinguished by little to no physical structure, little to no secondary behaviors, decreased awareness of speech problems and the aforementioned typical dysfluencies such as revisions and interjections.