Research in the UK & abroad

When does it begin?

Parents often tell us that their child started stammering around the time their language skills were developing.  This is typically between the ages of two and five years, although stammering can start later.

Stammering usually starts in childhood, often between the ages of 2 – 5 years coinciding with the rapid development of new physical and mental skills. In particular, the child is learning many new words, beginning to use longer sentences, expressing new ideas and asking lots of questions.

Stammering is different from other early speech and language problems because it can start at different stages in a child’s life.

For some it starts gradually – it comes and goes and seems to be a part of a child’s natural attempts to use more and more words. While for other children it can begin quite suddenly, sometimes almost overnight, and sometimes quite severely.

This can be very worrying indeed, for both the child and for their family. And, in some cases, it can disappear just as quickly, within days or months.

If you are concerned, it is best to seek advice early. Don’t be put off by the “don’t worry” school of thought. We all know that telling ourselves not to worry is usually unhelpful. Practical help is what is needed, which is what we are trying to offer here.

How does it work?

Stammering can take many different forms and each person who has a stammer shows slightly different features.

One common feature is its unpredictability and variability. This makes it a deeply frustrating problem to the person who stammers and to the family. Many parents describe how phases of stammering are followed by a fluent period which may last for weeks. Naturally, this adds to the dilemma of when or whether to ask for help.

What causes it?

Over the centuries, there have been countless theories about possible causes of stammering and there are researchers across the world who are trying to find out exactly what makes one child more vulnerable than another. Recently there has been growing evidence that genetics plays an important part, but not in all families.

Every child is unique. We use this diagram below to help understand the factors that might explain why a child starts to stammer, how the stammer changes over time, why children stammer more or less in particular circumstances and the impact that it has on the child and family. Everyone is born with their own physical ‘make-up’ and as we grow and develop, everyday experiences shape our personal characteristics, our strengths and our vulnerabilities. Each individual who stammers will probably have a different combination or ‘loading’ of these factors and these can change over time. The diagram below shows some examples of the factors that might be important for a child.

It can also be that this framework does not seem to fit; sometimes there seems to be absolutely no reason at all why a particular child continues to stammer. It is complicated and we will take each section in turn.

Has it got anything to do with a child's personality?

It is often assumed that people who stammer are shy or nervous. In actual fact, this is not true. Children and adults who stammer have exactly the same range of personality types as everyone else. However, stammering can affect a person’s self-esteem and confidence in some situations – and shyness or reticence may be the result of the stammering.

Many parents also describe their child as being overly sensitive, or a worrier or that he sets himself high standards. Although these traits do not cause the stammer, a child who is more sensitive to their stammering and more anxious about making mistakes may become upset when they can’t say what they want to say. Conversely, a child who is more laid-back and relaxed about life may not be so affected by moments of hesitancy or “bumpy talking”.

Genetics or inheritance

Here we are talking about the characteristics that the person is born with. Sometimes we read about “nature versus nurture”, the crossing point between what is inherited and the environment within which we are brought up.

For example, it can sometimes be quite easy to guess where eye colour or height came from with our own parents and grandparents. It is not so easy to explain personality traits, although you do hear people saying “stubborn, just like his grandad”! Character is probably a mixture of both “nature” and “nurture”.

Stammering also seems to be a mixture of both nature and nurture. For some there is a definite genetic link, a blood relative who has had or still has a stammer. It is becoming clearer that many children do inherit a vulnerability to stammering. At the Michael Palin Centre, more than half of the children we see have a blood relative who has either stammered in the past or continues to stammer. While researchers are trying to find out more about the genetic links, it will be many years before the picture is fully understood – or whether this will help us to decide which therapy is best for a particular child.

Does it change over time?

Stammering can change daily and from situation to situation and looking for signs that it is getting worse will increase your anxiety – and maybe the whole family’s. Trying to notice what the child is doing well is more helpful.

If you notice changes in your child’s speech it may be his or her attempt to speak more fluently. Throughout childhood, the range of speaking situations that a child encounters will increase and his or her awareness of the problem may be growing as a result. It becomes even more important to pay attention to the times when the speech is more fluent and notice what it is about those situations which seems to be helpful.

Has it got anything to do with the nervous system and speech fluency?

However, the research is also beginning to suggest (and we don’t know whether this is linked to genetics) that stammering may be a sign that the child’s developing nervous system for speaking fluently may be less efficient. The implication is that therapy will be more successful in childhood before the problem becomes “hard wired” into a more adult speech system. Children’s nervous systems for speaking continue to change and develop until early adulthood.

To quote Professor Anne Smith from Purdue University at the Oxford Dysfluency Conference in 2008:

Stuttering is a neurodevelopmental disorder involving many different brain systems active for speech – including language, motor, and emotional networks. Each infant is born with a genetic makeup that contributes to his or her probability of stuttering, however whether stuttering will develop depends upon experience. To learn to speak fluently, a child’s brain must develop many different neural circuits, and these circuits must interact in very precise and rapid ways. Stuttering emerges in childhood as a symptom that the brain’s neural circuits for speech are not being wired normally. For this reason, early intervention is critical, because by shaping the child’s experience, we can affect the ongoing wiring process in the child’s rapidly developing brain. The longer the stuttering symptoms persist in early childhood, the more difficult it is for us to change the brain’s wiring, and stuttering becomes a chronic, usually lifelong problem.”

Has it got anything to do with gender?

Boys are more vulnerable – we don’t know why, but boys are more at risk of other speech, language and literacy problems too.

Oral motor skills

This is related to the planning and co-ordination of the movements of articulation – tongue, jaw, voice box, etc. Some research studies have shown differences in the oral skills of some people who stammer – these may be slower or less well co-ordinated, but are so slight that they are imperceptible without scientific measuring equipment.

Brain functioning research

Brain imaging is a new and highly complicated area of research in adults who stammer. Early findings suggest that certain aspects of speech and language may be processed in different areas of the brain in some adults who stammer. What is not yet clear is whether this is at the root of the stammering problem or a result of difficulty in talking. Since it is not ethically possible to carry out these experiments with children, the results cannot be generalised to the younger population. This type of research will be continuing and we will keep you up to date with the latest studies.

Social and environmental factors

Throughout this website we emphasise that parents and families do not cause a child to stammer.  However a child’s environment is important as there are lots of things you can do to help.

Daily lifestyles, events, experiences, attitudes, and behaviours that occur at home and school do have an impact on all children in all sorts of ways, and for children who stammer this will include their fluency.

Most families’ daily lives are busy and demanding. There is so much to organize and to remember: full schedules of activities, clothes to find, mealtimes, bedtimes, appointments, school timetables, homework and social lives! There are constant demands and pressures, fun times and conflicts, anxieties and health worries – all normal parts of everyday life.

Some children who stammer may find it difficult to keep up the same pace, or keep trying to get in ahead of others.

However, the fact is that stammering and a fast pace do not go well together.

As adults, our task is to notice and understand the usual pace of life in the child’s environment and decide what can’t be changed and then try, where possible, to adjust those aspects which can be sensibly controlled or modified.


  • If everyone talks at once and at a rapid rate, the child may try to match it
  • If everyone uses very complicated language, the child may try to copy
  • If certain situations are demanding, the child may feel pressured

None of these is easy when you are also stammering.

The view that the environment plays an important role in a child’s stammering is supported by valuable clinical evidence which shows that helping families to notice what they are already doing that helps their child to be more fluent and doing more of this – can be really helpful for their stammering. Small changes can make a big difference to supporting the child’s fluency.

Speech factors

Parents often tell us that it seems like their child’s brain is going faster than their mouth. Speech and language skills develop differently for all children and this can contribute to a breakdown in the child’s fluency.

As was mentioned earlier, stammering generally emerges at a time when a child’s language system is developing rapidly. It has been suggested that this dramatic increase in language skills may overload the fluency system and supports the remark frequently made by parents that “his brain is going faster than his mouth”.

There does seem to be quite a lot of evidence linking children’s speech and language development to stammering. In fact, some researchers are fairly convinced that there may be an underlying speech or language problem which has been masked or hidden by the time the stammering starts.

Like all factors in stammering, this doesn’t seem to be the case for all children. Some are a bit slower in their talking while others seem to be very advanced. The researchers will have to explain that more clearly!

However, one thing that we do notice in the clinic is that when children try to use complicated language, they will often stammer more. Also when they are being asked to explain things, or are excited about retelling some story, perhaps trying to go quickly – then the fluency can break down.

Fluency seems to break down more frequently on longer words and in more complicated sentences. It is more likely to occur at the beginning of a sentence or phrase and with less familiar words.

English as an additional language

Over half the world’s population is estimated to be bilingual and about 8% of children start to stammer. Lots of children who stammer will therefore be learning to speak more than one language. However, being bilingual does not cause stammering and lots of children learn two languages and don’t stammer. For some children, learning two languages at once can be difficult to manage and may impact on their fluency. For advice on how to support your bilingual child who stammers click here.

Are people who stammer shy and nervous?

This is a popular misconception. In fact, there is exactly the same spread of personality types amongst those who stammer as in the whole population.

It is worth bearing in mind, though, that it is clear that the more anxious any speaker is, the less fluent they may become. This is especially true for many people who stammer.

Unfortunately stammering is often portrayed in this way by the media and in literature. Even in ‘Harry Potter’ books there are several references to characters ‘stammering nervously’. And the first question that we are asked by journalists is often: ‘Is stammering caused by nervousness?’

Stammering can affect a person’s confidence in some speaking situations and as a result the individual may seem to be more reticent or reserved. This has probably developed because of the unhelpful reactions of others to the stammer, based on misconceptions and a lack of understanding.

Can parents cause stammering?

Definitely not!

As parents, we all start to assume that everything we do is potentially wrong for our children, with guilt and worrying seeming to start as soon as the baby is born! There is apparently an innate drive that makes us all aim to be perfect parents, demanding that we are able to get it right.

This misconception about parents causing stammering seems to be related to some old, poor-quality research. An American speech pathologist (who had a stammer himself) developed a theory that the problem was caused by “highly anxious” parents labelling the normal hesitancies of developing speech as stuttering. Worse still, it was suggested that parents’ “negative reaction” to their child’s speech then caused the child to struggle to stop these moments of disjointed speech and that it was this effort that created the stammering.

There have now been countless research studies investigating whether parents of children who stammer do react or interact differently with these children – and the answer is quite clear:

Parents don’t cause stammering!

Can you catch stammering?


Some parents fear that their child might “catch” stammering from another child or adult. There is no research evidence that this is the case, and it would seem unlikely that children would opt to speak this way if they have the choice. Although, as with all aspects of this complex problem, there have been many anecdotes over the years.

Does it have something to do with intelligence?


It has often been suggested that people who stammer are either very intelligent or not so bright. The research tells us that there is no truth in either statement. People who stammer generally show the same spread of intelligence levels as the rest of the population.

Does it start when a left-handed child is forced to write with its right hand?

This was a compelling theory in the 1920s from the United States. It lasted for decades and some children went through periods with one hand tied behind their backs in an attempt to ‘undo the damage’. Eventually the theory was properly tested and there was no evidence to support it. Lots of children had been made to use their right hands without ‘knock-on’ effects at all. Left-handedness does not seem to be relevant.

If I draw attention to it, will I make it worse?

By talking about it calmly and naturally in the same way that you would talk about any other problem, you will prevent it becoming a taboo subject. By reassuring your child that it’s ok and that we all get stuck sometimes, you won’t make it worse.

A quiet acceptance and acknowledgement can make your child feel better. The message you want to convey to the child is that what they are doing is not unusual and that it’s part of the learning process. You want to convey the feeling of “I do understand”, “I am listening to you” and “I can help”.

How much more confusing and upsetting for a child is it when no one seems to be helping them with a problem they are struggling with? Imagine what’s going through their heads! “What’s wrong with me?” “Why can’t I talk properly?” “What am I doing wrong?” “Why aren’t they saying or doing something?”

If I ignore it will it go away?

Well, yes and no. Many parents receive this advice from friends and some professionals, however not all children will grow out of stammering. If the child is aware of the difficulties, is expressing concern or frustration with his or her speech, it is best to seek advice.

Many children are aware of their problem from an early age – children as young as three have described their stammering and the difficulties they are facing.

Suggestions and comments such as “there’s no hurry” and “I’m listening” can often be helpful and encouraging.

Is stammering just a phase?

It is true that many children do pass through a stage when it sounds as if they are stammering. This can last several weeks, or even months, and then they will become fluent again. It is estimated that up to four out of five children will overcome the problem. Some will need help while others grow out of it. There are some children who countinue to stammer and would benefit from specialist advice.

Note: The earlier help is provided, the more likely the child is to either overcome the problem or learn to manage it successfully.

Why can't my son say words beginning with the letter 'b'?

Unfortunately it is not as simple as that! It can often seem to be so but in fact there will be many occasions when ‘b’ words will be said fluently.

What may be happening is that the word beginning with that sound is an important one in the sentence. It carries much of the meaning and if it goes wrong the message may well be lost. Becoming more aware of certain sounds is more likely to be associated with:

– the first letter of a person’s own name
– another important person’s name
– making introductions
– certain key words in a sentence
– particular words that can’t be avoided easily

Of course, when we have begun to notice particular sounds or words, they seem to crop up all the time, but that is because they have become particularly important. It is a vicious circle.

Why does the stammer disappear sometimes and then return in certain situations?

This often happens and can make stammering incredibly frustrating and confusing for some.

It is often easier to talk to people who are familiar. Particularly if they are used to the stammer and accept it easily. On the other hand, strangers or people who are ‘important’ in some way can make the person feel more anxious about stammering. This leads to greater efforts to avoid or hide it. This increase in tension will in turn increase the likelihood of the stammer occurring.

We all react with increased tension in certain situations and the result can mean that we don’t function quite as well as we would like.

Why don't people understand? Why are they so unkind?

Sadly this does happen sometimes.

There is a real lack of understanding amongst people who have no personal experience of stammering. While many people are very thoughtful and helpful and try to do the right thing, at other times people who stammer can be faced with people who are prejudiced and intolerant of communication (and other) problems.

Individuals who stammer are likely to experience times when other people do react in a negative way. Sometimes they may give unhelpful advice, make unkind comments and worst of all, tease or ridicule. While these reactions don’t always happen, they will make the individual very self-conscious and will heighten their anxiety about talking.

It is through these unhelpful reactions that ‘fears’ can develop about speaking, which may become part of the problem. After all, many of us might be worried about being labelled ‘nervous’, ‘stupid’ or ‘inferior’ and would quickly lose confidence if we were.

Furthermore, being told not to worry about what other people think or say, while well meant, is usually very difficult or impossible to put into practice.

Why is my daughter's stammer quite different now that she is a teenager?

This often happens.

Sometimes, in order to avoid or minimise the problem, a person who has been stammering for a while may develop some very resourceful coping strategies, for example:

– developing a wide vocabulary of alternative words so that ‘difficult’ words can be avoided
– using a ‘starter’ word or phrase which gives a ‘run up’ to the word they want to say
– using a physical gesture – moving a hand or foot, as if to “push” the words out.

While these can be quite helpful strategies, they can also become part of the problem too. A trick that may have helped for a while stops being so useful, but like many habits, it can become a way of life.

We really don’t recommend advising a child or an adult to “think of a new word” or “take a deep breath”. While it seems to help for a short time, it may eventually make the problem worse.

Avoidance and coping strategies take a great deal of mental energy – it is exhausting to have to concentrate on how you are speaking all the time, rather than on what you are trying to say.


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