Abnormalities in speech motor control.
- Neuroimaging studies using PET scans or functional MRI to examine adults who stutter have shown different patterns of brain activation during stuttering and even at rest. Stutterers show more activation of right hemisphere areas of the brain.
- Most non-stuttering speakers use the left side of their brains to plan and initiate speech. Actually, the part of the brain that controls speech motor planning and execution is only located in the left hemisphere – Broca’s Area. So the left hemisphere controls analytic thinking and sequencing – skills that are necessary for speech and language production.
- The right hemisphere, on the other hand, supports abstract perceptions and emotions. So people who stutter may be using the wrong hemisphere.
- Some evidence indicates that abnormalities in speech motor control, such as timing, sensory and motor coordination are also different in people who stutter.
- Stuttering tends to run in families. It appears that stuttering can result from inherited (genetic) abnormalities in the speech and language centers of the brain.
- Stuttering can sometimes result from a stroke, trauma or other brain injuries.
Notice that these causes are all physiological differences between stutterers and nonstutterers. The cause is not emotional anxiety or nervousness.
Here are some of the myths about stuttering causes that many people unfortunately still believe.
- Stuttering is caused by children’s parents – many parents blame themselves. In the 1930’s this was the belief before scientific research dispelled the myth.
- Caused by drawing attention to a child’s normal disfluencies – this was the logic of the unresearched 1930’s theory.
- Stuttering is a psychological problem
- Caused by reduced intelligence or shyness
- You can “catch” stuttering by imitating another child who stutterers.
- A traumatic event in childhood causes stuttering.