What Causes Stammering? Understanding the Brain and Speech Development
We’re going to get a little bit scientific in this blog post but don’t worry, you don’t need any background knowledge! Understanding how the brain develops can help explain the possible causes of stammering and why children’s speech can change over time.
Stammering (also called stuttering) in children is neurodevelopmental in nature. That might sound complicated, but it simply refers to how the brain develops and how different brain systems communicate with one another. Understanding a little about the brain can help explain why stammering in children can be so variable throughout childhood.
How the Brain Works When We Speak
Speaking is one of the most complex things humans do. It requires multiple areas of the brain to work together very quickly and efficiently. These areas are responsible for:
Planning what we want to say
Finding the right words and then the right sounds
Coordinating breathing, voice and mouth movements
Monitoring what we hear and adjusting speech in real time
The brain is made up of:
Grey matter – the areas that do the “work”, such as speech planning, language and motor control
White matter – the pathways that connect these areas together
For speech to feel easy, these areas need to communicate smoothly. Research shows that when comparing the brains of people who do and don’t stammer, there are small differences in how these connections are organised. This doesn’t mean anything is “wrong” with the brain. It simply means it is wired slightly differently.
This is why promises of a miracle “cure” for stammering can be so frustrating. Childhood stammering reflects how the brain is wired. Just as people differ in coordination, musical ability or processing speed, brains also differ in how efficiently they manage speech.
As children learn to talk and develop, the pathways in their brain strengthen. This is why many children naturally stop stammering. As these connections become more efficient, talking can feel easier and stammering may reduce. For some children, these connections do not strengthen in the same way over time. This is simply how their brain is wired, and their stammer may continue into adulthood.
We also know that the more children practise talking, the more these connections strengthen and the easier talking can feel, regardless of whether the stammer fully resolves or not. Children’s brains are especially malleable.
Brain Development and Childhood Stammering
Children’s brains are still under construction. Speech- and language-related brain areas develop over a longer period of time than many other skills.
Research shows that:
Grey matter in speech-related regions continues to mature into late childhood
It peaks around age 10 in girls and around age 12 or later in boys
After childhood, grey matter volume gradually reduces as the brain becomes more efficient
White matter connections continue to strengthen well into adulthood, even up to mid-life
This is all part of typical development and helps explain why many children who stammer in early childhood naturally stop stammering as their brains mature. Children’s brains are highly adaptable, a concept known as neuroplasticity, meaning they change in response to growth, learning and experience.
Processing Load, Brain “Traffic” and Fluency
A helpful way to understand stammering is to think of brain connections as roads. A colleague once used this analogy, and it often helps families make sense of why stammering changes in different situations.
Grey matter areas are like destinations
White matter pathways are the roads connecting them
Speaking is the traffic moving between them
Some people have wide, fast “motorways” that cope well with lots of traffic. Others have narrower “country roads” that become congested more easily.
When there is low traffic, such as in calm, familiar situations with little time pressure (for example, being at home during the holidays), speech is often easier and more fluent.
When there is high traffic, such as at family gatherings, speaking in front of the class or in a busy meeting, talking can become harder. Processing load increases when a child who stammers is:
Tired or unwell
Using more complex language
Excited, anxious or upset
Competing for speaking time
In busy or noisy environments
Children who stammer are more sensitive to increased processing load. Trying to force speech through a traffic jam often makes things harder rather than easier. This is why pressure, rushing or telling a child to “slow down” can unintentionally increase stammering.
In therapy, especially with children and teenagers, we often focus on reducing load when demands are high or adapting communication to make talking feel easier. The aim is not perfect fluency, but helping children feel more relaxed and confident when communicating.
What Is Typical? Stammering vs Normal Dysfluency
No one is fluent all the time. All children, and adults too, show everyday dysfluencies such as:
Hesitations
Revisions (for example, “I want… no, I mean…”)
Interjections (such as “um” or “er”)
Phrase repetitions
Stammering becomes more noticeable when there are core stammering features, such as:
Repetition of sounds or syllables
Prolonged sounds
Blocks where no sound comes out
Stammering is a normal variation in human communication, not a fault or failure. Around 5% of people stammer at some point in their lives, and about 1% stammer at any given time. That is roughly the same percentage as people with red hair. We all know someone with red hair, which means we almost certainly also know someone who stammers.
What Causes Changes in Fluency?
Changes in fluency often reflect changes in brain load rather than motivation or effort. Fluency can vary depending on:
Brain development
Processing load
Environmental demands
Fatigue or illness
Emotional factors such as excitement or anxiety
This is why stammering in children can fluctuate from day to day or situation to situation.
A Key Takeaway: Supporting Children Who Stammer
Stammering in children is best understood as a difference in how the brain manages speech under load. For many children, changes in fluency are part of natural brain development.
The most important role of adults is not to “fix” the speech, but to reduce pressure, create space for talking and support confident communication, with or without stammering.