Stammering and Speech Impediment

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Stammering, or stuttering, is a speech impediment and problem relatively common which occurs in childhood and can persist into adulthood.

How to recognise developmental stammering
Causes of stammering
Diagnosing a stammer
Treating a stammer


Stammering is characterised by the repetition of sounds or syllables (such as saying ‘mu-mu-mu-mummy’), prolonging sounds (mmmmmmummy) and pausing or ‘blocking’ for a long time between words.

It usually occurs at the beginning of speech, and individuals will often avoid words or speaking situations to try to hide it.

It varies in severity from person to person.Also, a person will find they have periods of severe stuttering followed by times of relatively fluent speech.

Types of stammering

There are two main types of stammer:

  • Developmental stammering. This is the most common type of stammering, which many people are familiar with. It develops during childhood as a child is learning to speak, usually beginning around the age of three-and-a-half years.
  • Acquired or late-onset stammering. This can occur in adults as the result of a severe head injury, stroke or progressive neurological disease (disease affecting the nerves). It can also be caused by certain drugs or medication, or psychological or emotional trauma.

The rest of this article will focus on developmental stammering.

How common is developmental stammering:

Stammering is common in young children. Estimates for developmental stammering vary, but it is expected that 5-8% of pre-school children will experience a phase of non-fluent speech.

The condition is more likely to persist in males than females, which is why there are four times more men than women with a stammer. The reason for this is unclear.

All ethnic groups are affected equally by stammering.

The causes of stammering are still uncertain, but evidence suggests that inheriting certain genes may increase a child’s likelihood of developing a stammer.


About three in four cases of developmental stammering in pre-school children will resolve without treatment.

One out of four will need treatment to prevent a persistent stammer developing. At this pre-school stage, treatment is still highly successful in resolving stammering completely, especially if it is received as soon as possible. Stammers are much less likely to be totally eliminated in children aged six or seven or more.

A speech and language therapist is qualified to determine which children are likely to recover naturally and which need treatment, so an early referral is essential.

Without adequate treatment, about 1% of older children and teenagers will have developed a persistent stammer. It is estimated that 1 in every 100 adults has a stammer.

Some adults find that their stammering improves as they get older. Many will have learnt to control their stammer for most of the time, although certain ‘triggers’ may make them stammer more, such as stress or having to speak in public.

There are many different speech and language approaches for stammering, which can help people improve their fluency and communication skills.

Electronic ‘anti-stammering’ devices are also available and can be helpful. These are designed to help people control their voice by providing sound feedback.For more information, see Stammering – treatment.

How to recognise developmental stammering

Developmental stammering usually involves some obvious outward signs and some less obvious signs.

Outward signs are:

  • repeating certain sounds, syllables or words when speaking, such as saying ‘a-a-a-a-apple’ instead of ‘apple’
  • prolonging certain sounds (not being able to move on to the next sound), for example, ‘mmmmmmmmmmilk’
  • lengthy pauses between certain sounds and words, which can make it seem as though a child is struggling to get the right word, phrase or sentence out
  • using a lot of ‘filler’ words during speech, such as ‘um’, ‘ah’ and ‘you know’
  • avoiding making eye contact with other people

Stammering is usually worse in situations where the child is conscious of their speech and may be trying hard not to stammer. Such situations might include:

  • talking to a person in authority, such as a headteacher
  • giving a presentation at school or college in assembly or in class
  • reading aloud
  • speaking on the telephone
  • saying their name in registration at school

Associated behaviours

A child with a stammer may develop some associated behaviours, which may include:

  • involuntary physical movements, such as eye blinking, jerking the head or jaw, clenching the teeth or fists, or having body spasms

Hidden signs may be:

  • deliberately avoiding saying certain sounds or words known to provoke a stammer
  • avoiding situations because of fear of stammering,for example, not asking for items in shops or not going to birthday parties
  • changing the style of speech to prevent stammering, for example,talking very quickly or in an unusual tone of voice
  • feeling negative emotions because of stammering, such as fear, frustration, shame and embarrassment

Causes of stammering:

The exact cause of stammering is still unclear. Most experts think there areseveral possible factors that can trigger stammering in children. These factors are described below.


Cases of stammering have been known to run in families. For example, if an identical twin has a stammer, there is a 70% chance that the other twin will also stammer.

This suggests that the genes a child inherits from their parents might cause them to stammer.

Research carried out in 2010 identified a number of specific genetic mutations (faulty genes) that were common in adults of Pakistani origin who had a persistent stammer and who had other family members affected by stammering.

It is unlikely that there is one gene responsible for stammering. It is more likely that a problem in acquiring speech and language runs in families and manifests itself in stammering behaviour.

There is evidence that stammering is two to three times more likely in males than females. This links with other research about developmental disorders, which boys appear to be more likely to experience than girls. Girls are also more likely to overcome their stammer naturally.

Cognitive activity

Cognitive activity is a medical term used to describe the many different mental processes that occur in the human brain.

Researchers have used magnetic resonance imaging (MRI) scanners to study the brains of adults with a persistent stammer. MRI scanners use strong magnetic fields and radio waves to produce a detailed image of the inside of the body.

The brain scans revealed that the pattern of cognitive behaviour was different in the brains of adults who stammer. In particular, there were:

  • low levels of activity in a part of the brain called the left temporal lobe, which is involved in processing sound and speech
  • unusually high levels of activity in the right hemisphere (in most adults, the left hemisphere is active when a person is speaking)

These results have led to a number of theories about how these abnormal patterns of cognitive activity may contribute to stammering.

First, the low levels of activity in the left temporal lobe may mean that a person has an impaired feedback system. This may cause differences in the way they hear their own voice.

Second, the abnormal activity in the right hemisphere may mean that a person who stammers has interference from this part of the brain when they are speaking.

However, it is unclear whether these effects are the result of stammering or the cause of stammering.

Basal ganglia

Another area of research has focused on a part of the brain known as the basal ganglia. The basal ganglia is responsible for some of the most basic human abilities and for processing powerful emotions such as fear and aggression.

Brain scans have shown unusual activity in the basal ganglia in adults who stammer. It may be that their stammering is caused by a problem with regulating the functions of the basal ganglia.

It is not known if this unusual cognitive activity is found in children who stammer, as no brain scans involving children have been carried out.

Diagnosing a stammer:

When to seek medical advice

It is common for young children to have some degree of difficulty with their speech.If younotice that a child repeats certain words and sounds, or if they pause between words and sounds, it does not necessarily mean they have a stammer.

An American organisation, the Stuttering Foundation of America, has created a questionnaire that has been designed to help parents distinguish between normal speech problems and a stammer. The questionnaire consists of 10 questions:

  • Does your child repeat parts of words rather than whole words or entire phrases, for example ‘b-b-b-banana’?
  • Does your child repeat sounds more than once every 8 to 10 sentences?
  • Does your child have more than two repetitions, for example ‘a-a-a-a-apple’ instead of ‘a-a-apple’?
  • Does your child seem frustrated or embarrassed when he or she has trouble with a word?
  • Has your child been stammering for more than six months?
  • Does your child raise the pitch of their voice, blink their eyes, look to the side or show physical tension in the face when stammering?
  • Does your child use extra words or sounds like ‘uh’, ‘um’ or ‘well’ to get a word started?
  • Does your child sometimes get stuck so badly that no sound at all comes out for several seconds when they try to talk?
  • Does your child sometimes use extra body movements, like tapping their finger, to get sounds out?
  • Does your child avoid talking, use substitute words or stop talking in the middle of a sentence because they are worried they may stammer?

The more of these questions you answer with ‘yes’, the more likely it is that your child has a stammer and may benefit from a referral to a speech and language therapist.

Speech and language therapy

A speech and language therapist (SLT) is a health professional who specialises in treating speech disorders such as stammering.Your GP will be able to refer you to your nearest speech and language therapy service.

However, in most areas of the UK, the speech and language therapy service operates a self-referral system, so you can contact them directly. The British Stammering Association’s (BSA) Information Service can provide contact details of local speech and language therapy services.

While some cases of stammering may easily be diagnosed by listening to a child speak, it is recommended that parents consult a specialist SLT if they have concerns.

The SLT will assess your child’s speech and, if necessary, will recommend a course of therapy that is made specifically for your child, taking into account their speech presentation and stage of development.

It is important to note that there is no evidence that parents cause their child’s stammer.

Treating a stammer:

There are many different treatments available for stammering.

Some of the most commonly used treatments are described below.

Demands and Capacities Model

It is still unknown why a child will start to stammer at a certain point. One model to explain this is called the Demands and Capacities Model.

The Demands and Capacities Model suggests that, if the demands on the child’s speech are greater than the child’s physical capacity to produce this level of talking, then fluency of speech(in children with a tendency towards stammering)can break down.

These ‘demands’ are often made by the child. They put pressure on themselves to communicate in a way they can’t yet manage.The pressure is not caused by over-anxious or demanding parents.

The goal is to create an environment in which a child feels more relaxed and confident about their use of language. This involves:

  • speaking slowly to the child
  • developing a child-parent interaction
  • avoiding criticising or drawing attention to the child’s stammer
  • trying to make the family environment as relaxing and calm as possible

Direct therapy

Most speech and language therapists (SLTs) recommend direct therapy for cases of moderate to severe stammering that do not appear to be resolving over time.

A widely used type of direct behavioural therapy used to treat pre-school children is called the Lidcombe Programme.

The Lidcombe Programme is designed to be carried out by the parents of the child and is based on the principle of providing consistent feedback to the child about their speech in a friendly, non-judgemental and supportive way.

Stammering that persists beyond the age of seven tends to be more challenging to treat and often requires a more intensive approach, perhaps using group therapy.

Other therapy options

There are other therapy options more appropriate to adults and those with acquired or late-onset stammering. These include psychological therapies and feedback devices.

Psychological therapies include solution-focused brief therapy (SFBT), personal construct therapy and cognitive behavioural therapy (CBT). CBT is not used to treat stammering directly, but may be useful if feelings of stress and anxiety make stammering worse. During a course of CBT, your therapist may ask you what situations make your stammer worse, and your thoughts and feelings about those situations.

Feedback devices alter the way the voice is heard. They include:

  • delayed auditory feedback (DAF), which plays your voice back to you a fraction of a second after speaking
  • frequency-shifted auditory feedback (FSAF), which plays your voice back to you at a lower or higher frequency
  • combined DAF/FSAF devices, which use a combination of both methods

The British Stammering Association (BSA) remains the main support organisation for people with a stammer in Britain and has a comprehensive and informative website.