Stuttering affects nearly 3 million people of all ages in the United States. As children begin to develop their language skills, up to 10% will experience a stutter for some period of their life.
The majority of children who stutter, approximately 75%, will outgrow their stutter eventually over several months or years. For the remaining children, stuttering can persist into adulthood if left untreated, potentially turning into a lifelong communication disorder.
But what exactly are the causes of stuttering? Let's look at the risk factors and why stuttering occurs.
What is stuttering?
We all misspeak from time to time or have natural sound repetitions. Occasional stutters (also called disfluencies) are not considered clinical stuttering. Clinical stuttering is when a person consistently produces disfluencies, or interrupted speech. A person who stutters has trouble producing sounds and words smoothly, or fluently.
What does stuttering sound like?
Let’s review the different types of stuttering.
Repetitions: Repetitions are a type of disfluency where a word, syllable, or sound is repeated more than three times. Example: “I w-w-w-w-w-w-want to go to the store.”
Prolongations: Prolongations are a type of disfluency where a sound is prolonged or held for an abnormally long period of time. Example: “I fffffffffffffffffound a penny.”
Blocks: The last kind of disfluency or stutter is called a block. When a block occurs, no sound is made in the mouth or throat. The parts of the mouth are stuck in one position and unable to continue to move for a period of time. Example: “I w------------------ant to go to the park.”
Now that we have covered the basic types of disfluencies, let’s discuss some of the most common causes of stuttering.
What causes a stutter?
Genetics and family history
Research has demonstrated that there is likely some kind of genetic relation to stuttering. Case histories have shown that many people who stutter also have family members who stutter. However, the National Stuttering Association has also stated that there does not seem to be a link between the severity of stuttering in family members.
In other words, a person may be more likely to stutter if they have family members who stutter. Yet each family member may experience different levels of severity.
Motor planning and brain function
There is reason to believe that those who stutter have differences in speech-motor control, such as coordination and timing. Abnormalities in these areas can result in stuttering.
According to the National Stuttering Association, brain imaging studies have also shown that those who stutter have more right brain activity than left brain activity. Language is processed and planned in the left hemisphere. Less activity in the left brain may negatively impact a person’s speech fluency.
There is research to suggest there could be a connection between language processing/word retrieval and stuttering. People who do not stutter have shown better abilities in receptive language as well as word retrieval. Those who stutter have shown more problems tied to word finding. An increase in response times can increase chances of stuttering due to stalling of speech, and possibly even perceived pressure to speak faster.
It's not uncommon for those who stutter to have a tough time speaking in an environment that's tense or emotional. Likewise, some people may find that they stutter more often around people of certain personalities.
Because of heightened emotion or anxiety, breathing can sometimes become more shallow or inconsistent. The vocal tract and articulators may also exhibit more tension because of this. We review more about breathing in the next section.
What physically happens during stuttering?
Now that we've covered some of the root causes of stuttering, let’s explore what physically happens in a stuttering event, and how this negatively impacts speech fluency.
Speech begins with breath. We inhale and we exhale. As we breath out, our vocal folds come together and vibrate when we use our voice. The air we breathe out and the vocal folds work together to produce adequate sound. That sound is then shaped in the oral cavity to produce different types of sounds. For example, when we pronounce the /d/ sound, the tongue comes up and taps behind the teeth. When pronouncing /r/, the tongue tenses and moves backward in the mouth.
If there is tension in any area of the mouth or throat, this can cause stuttering.
If a person is stuttering on the /d/ sound, and repeating it over and over, then there is likely tension in the tongue muscles.
If a person is trying to say the /f/ sound and it's coming out as a prolongation (example: “ffffffff”), then there could be tension in the lips or jaw contributing to the stutter.
Breathing exercises to help with stuttering
It's important to note that there could also be a lack of breath support involved. If we do not have enough air (breath) to speak on, it can feel like we're trying to squeeze out every sound. This can cause tension.
Appropriate breathing for speech is called diaphragmatic breathing. It's also referred to as belly breathing. This is because when we take diaphragmatic breaths, the diaphragm moves downward. This allows our lungs to expand as we breathe in, then moves back in place as we breathe out.
You can try this yourself. Before you take your first breath, place your hand on your belly. You should be able to feel your belly move out, then back in. If your hand moves in this pattern, you will know that you're breathing correctly!
When using this type of breathing during speech, make sure to control your breath. This means that you should be able to speak during one exhalation without feeling like you're running out of air. This takes practice for those who struggle in this area. However, once it is learned, it will do a lot to help the smoothness of your speech!
How to manage a stutter and speak more smoothly
There are many resources available for additional education about stuttering, along with techniques you can practice at home or with a speech therapist to improve fluency. To start, we've compiled an in-depth resource guide that answers some of the most foundational questions about stuttering. We also offer a series of helpful videos from licensed speech therapists about stuttering in both children and adults.