Citing this article
This page contains an article about children's speech sound disorders. Cite it as:
Bowen, C. (1998). Children's speech sound disorders: Questions and answers. Retrieved from http://www.speech-language-therapy.com/phonol-and-artic.htm on (date).

Introduction

What is speech?
Speech is the spoken medium of language. The other two "mediums" or "forms" of language are writing and gestures. Gestures range from simple iconic movements, like pretending to drink, through to complex finger-spelling and sign systems.

What is phonology?
Phonology is a  branch of linguistics. It is concerned with the study of the sound systems of languages. 

The aims of phonology are to demonstrate the patterns of distinctive sound contrasts in a language, and to explain the ways speech sounds are organised and represented in the mind. 

The term "phonology" is used clinically as a referent to an individual’s speech sound system - for example, "her phonology" might refer to "her phonological system", or "her phonological development".

What is phonological development?
The gradual process of acquiring adult speech patterns is called phonological development.

Putting it another way, the emergence in children of a properly organised speech sound system is called phonological development.

Phonological development involves three aspects:

the way the sound is stored in the child’s mind;
the way the sound is actually said by the child;
the rules or processes that map between the two above.

How easy should it be to understand young children's speech?
Table 1 provides a rough rule of thumb for how clearly your child should be speaking. Bear in mind that there is considerable individual variation between children. If you are in doubt about your own child's speech sound development an assessment by a speech-language pathologist will quickly tell you if your child is 'on track' and making the right combination of correct sounds and 'errors' for their age.

What are the characteristics of young children's speech?
All children make predictable pronunciation errors (not really 'errors' at all, when you stop to think about it) when they are learning to talk like adults. These 'errors' are called phonological processes, or phonological deviations. Table 2 displays the common phonological processes found in children's speech while they are learning the adult sound-system of English. Further detail is provided on the typical speech acquisition page.

By what ages are phonological processes typically eliminated?
Phonological processes have usually 'gone' by the time a child is five years of age, though there is individual variation between children. Table 3 lists the ages by  which each of the processes are normally eliminated.

What is articulation?
Articulation is a general term used in phonetics to denote the physiological movements involved in modifying the airflow, in the vocal tract above the larynx, to produce the various speech sounds. Sounds are classified according to their place and manner of articulation in the vocal mechanism (Crystal,1991). 

What are articulation development and phonetic development?
The terms 'articulation development' and 'phonetic development' both refer to children's gradual acquisition of the ability to produce individual speech sounds. In Table 4 is an outline the ages by which children use individual consonants with 75% accuracy during conversation. more here

How are phonological and phonetic development related?
There is a complex relationship between phonological and phonetic development. Normal speech development involves learning both phonetic and phonological features. 

The bulk of recent research into children’s speech development has dealt with phonology: exploring and attempting to explain the process of the elaboration of speech output into a system of contrastive sound units. In recent years, there has also been a considerable body of research into the acquisition of motor speech control, bringing with it a renewed interest in the nexus between phonological development and phonetic development.  

Phonological development and phonetic mastery do not synchronise precisely. A common example of this asynchrony, referred to by Smith (1973) as the puzzle phenomenon, is provided by children who realise /s/ and /z/ as 'th' sounds, while producing "th-words" with [f] in place of voiceless 'th', and [d] or [v] in place of /ð/.

Developmental Phonological Disorders

What are developmental phonological disorders?
Developmental Phonological Disorders or "phonological disorder", are a group of language disorders, whose cause is unclear, that affect children’s ability to develop easily understood speech patterns by the time they are four years old. Developmental phonological disorders can also affect children's ability to learn to read and spell.

Are there other names for 'developmental phonological disorders'?
Developmental phonological disorders are known by many names including 'phonological disorder' and 'phonological delay', and 'phonological impairment'. 

Why do SLPs call the same thing by different names?
Good question!

Phonological processing disorder??!
There are two terms that are not included in the list of synonyms. They are "phonological processing disorder" and "phonological processes disorder". Despite their wide usage, these incorrect (and misleading) terms are not synonyms for developmental phonological disorder. Neither are they names for closely related speech sound disorders. They are "made up" terms that have somehow crept into listservs and discussions. Even SLPs sometimes use them!

Are developmental phonological disorders something new?
No. In the past, a phonological disorder was termed a 'functional articulation disorder', and the relationship between it and learning basic school work (like reading and spelling) was not well recognised. Children were just thought to have difficulty in articulating the sounds of speech. Traditional articulation therapy was used to rectify the problem. 

Is 'developmental phonological disorder' a 'functional articulation disorder' under a different name?
'Developmental phonological disorder' is not simply a new name for an old problem. The term reflects the influence of psycholinguistic theory on the way speech-language pathologists now understand phonological disorders. Nowadays, the traditional diagnostic classification of 'functional articulation disorder' is falling into disuse. 

Children with phonological disability are usually able to use, or can be quickly taught to use, all the sounds needed for clear speech - thus demonstrating that they do not have a problem with articulation as such. In other words, we now know that the problem is not a motor speech disorder. more here

Just to complicate matters, however, some children with developmental phonological disorders also have difficulties with fine motor control and/or motor planning for speech.

What is traditional articulation therapy?
There is no single definition of traditional articulation therapy. It is a term that is applied to a number of therapy approaches that focus on the motor aspects of speech production, with or without auditory discrimination training. 

In essence, traditional articulation therapy involves behavioural techniques, focused on teaching children new sounds in place of error-sounds or omitted sounds, one at a time, and then gradually introducing them (new sounds that is) into longer and longer utterances, and eventually into normal conversational speech.

Is traditional therapy still an acceptable form of treatment?
Traditional therapy techniques, using the format outlined above, have withstood the test of time, and can still be very suitable for children with functional speech disorders.

What is a functional speech disorder?
A functional speech disorder is a difficulty learning to make specific speech sounds. The index page for a series of articles about functional speech disorders is here.

Children with just a few speech-sound difficulties such as lisping (saying 'th' in place of 's' and 'z'), or problems saying 'r', 'l' or 'th' are usually described as having functional speech disorders. But, you guessed it! There are synonyms for this too. Functional speech disorders are often referred to as 'mild articulation disorders' or 'functional articulation disorders'. Examples include:

The word super pronounced as thooper.
The word zebra pronounced as thebra.
The word rivers pronounced as wivvers.
The word leave pronounced as weave.
The word thing pronounced as fing.
The word those pronounced as vose.

NOTE: 
Some of these sound changes are acceptable in a number of English dialects.

Is traditional articulation therapy an appropriate approach to treating developmental phonological disorders?
The traditional approach is unsuitable for children with developmental phonological disorders. SLP's who include phonological principles in their theory of intervention believe that a 'phonological approach' should be used with children with phonological disorders. 

Phonological approaches to intervention, of which there are several, are called 'phonological therapy'.

What is phonological therapy?
The term phonological therapy refers to the application of phonological principles to the treatment of children with phonological disability. Phonological therapy:

1. is based on the systematic nature of phonology;

2. is characterised by conceptual, rather than motoric, activities;

3. aims to facilitate age-appropriate phonological patterns through activities that encourage and nurture the development of the appropriate cognitive organisation of the child’s underlying phonological system; and,

4. has generalisation as its ultimate goal.

Where does the problem (of phonological disorder) lie?
In essence, the child with a developmental phonological disorder has a language difficulty affecting their ability to learn and organise their speech sounds into a system of 'sound patterns' or 'sound contrasts'. The problem is at a linguistic level, and there is no impairment to the child's larynx, lips, tongue, palate or jaw.

Does that mean there is no such thing as an articulation disorder?
Unfortunately, no. Children with "dyspraxia" (Childhood Apraxia of Speech) or a dysarthria have articulation disorders (or motor speech disorders). Children with anatomical (structural) differences such as cleft lip and palate, tongue-tie or other cranio-facial anomalies may also have articulation disorders.

Childhood Apraxia of Speech

What is dyspraxia?
Let's start with a reminder about what it is not! Childhood Apraxia of Speech is a childhood speech disorder. It is NOT the same as "Apraxia" or "Dyspraxia" in adults who have had strokes or head injuries. 

Children with dyspraxia (or apraxia - both terms are as "correct" as any of the others listed below) have the capacity to say speech sounds but have a problem with motor planning. They have difficulty making the movements needed for speech, voluntarily. 

Dyspraxia can be mild, moderate or severe. It can apparently resolve with appropriate therapy, in that the person's speech sounds acceptable, though the underlying deficit probably remains forever. Alternatively, it can persist for a lifetime, in the form of very little speech and / or very difficult to understand speech, despite a great deal of appropriate therapy.

Is dyspraxia in children called by different names?
Dyspraxia in children is known by various names:

apraxia
apraxia of speech
developmental apraxia of speech [DAS]
childhood apraxia of speech [CAS]
suspected childhood apraxia of speech [sCAS]
developmental verbal dyspraxia [DVD]
developmental articulatory dyspraxia [DAD]

Why is CAS in children called by different names?
On close reading of the literature, all the CAS 'names' seem to mean the same thing when it comes to looking at the actual symptoms or features of the child's speech production, mouth movements and slow progress acquiring speech. The most commonly used names for it are probably: developmental apraxia of speech [DAS], developmental articulatory dyspraxia [DAD], and developmental verbal dyspraxia [DVD]. Childhood Apraxia of Speech [CAS] is an insurance friendly newcomer that has rapidly currency in the United States in recent years, and in the contemporary research literature where the terms CAS and sCAS are used and preferred.

In general each of these terms refer to children who have the capacity (the neuro-muscular wherewithal, if you like) to say speech sounds but who have a problem with motor planning. Messages from the brain, intended to tell the speech mechanism (larynx, lips, tongue, palate and jaw) what movements to make to produce speech, do not occur easily for children with dyspraxia. This difficulty comprises both a motor planning problem AND a difficulty 'retrieving' speech sounds and patterns when they are required.

The characteristic speech of such children includes differences in the rhythm and timing (prosody or 'melody') of speech and inconsistent speech sound errors. The distinguishing characteristic of apraxia of speech is that it is a problem with motor speech planning and programming, with NO weakness, paralysis or poor co-ordination of the speech mechanism.

It is probably safe to say that that whether researchers or clinicians call the disorder DAS/CAS/sCAS, DAD or DVD, they would ALL agree that the features outlined above are characteristic of the speech problem they are studying, assessing or treating.

It is also probably true to say that whatever term is being used to name the problem, experienced clinicians at the 'grass roots' level will be drawing on a very similar range of therapy techniques and activities.

All of which begs the question: so why call the problem by different names? There are at least five main THEORIES that attempt to explain the basis of developmental apraxia. 

(1) It is due to an auditory processing problem 
(2) It is a very specific 'specific language impairment' affecting language acquisition at the sound-syllable-prosody level 
(3) It is due to an organisational problem with sequencing the movements required for speech  
(4) It is due to a difficulty with making volitional (pre-planned, if you like) movements for speech production 
(5) It is due to various combinations of these factors.

Importantly, these are THEORIES that are currently being formulated and tested by speech scientists. The fact is, we do not yet have a watertight explanation for dyspraxia.

Many clinicians and researchers actually working with children in the "apraxia population" who use the terms DAS and DAD tend to be those who veer towards the "motor based" explanation. 

Those who use the term DVD tend towards a "language based" explanation. Some clinicians use the terms DAS and DVD interchangeably. Some, who embrace the probability that the problem might be "linguistic" and "motor" in origin use DVD/DAS. 

Those who use the term CAS are probably au fait with the current research literature and current thinking about the disorder.

Then again, there are clinicians who use terms such as these because they have dropped into their clinical vernacular, in which case the term used does not reflect a particular theoretical orientation.

What are the characteristics of Childhood Apraxia of Speech?
To recapitulate, the distinguishing characteristic of childhood apraxia of speech is that it is a problem with motor speech planning and programming, with NO weakness, paralysis or poor co-ordination of the speech mechanism.

Some authorities believe that the primary difficulty children with dyspraxia have is with volitional (voluntary) movements of the speech production mechanism.

Children with CAS, if they are able to talk, usually make very variable articulation errors, their speech is slow, it seems very effortful to an onlooker, and there is a lot of 'trial and error' involved in trying to make particular sounds. The rhythm of speech usually seems wrong to the listener, and the child seems to put the emphasis in all the wrong spots (that is, there is something obviously unusual about their prosody).

The key features that alert a speech-language pathologist to the possibility of a CAS diagnosis in a young child are these:

1. The child may have no words, very few words, or up to 100 to 200 words in their vocabulary. They are unlikely to be attempting to make more than a handful of 2-word combinations.

2. Some give the impression of struggling to talk, exhibiting trial and error attempts to say words, accompanied by great frustration.

3. Many use self-taught signs and gestures to augment communication, which may include a lot of ingenious body language and facial expression. They MAY use a lot of mime and gesture to communicate. Some augment signs and gestures with a repertoire of sound-effects (car noises, and the like) to good effect.

4. Their speech has several of these characteristics:

   1. Words, in general, are not clearly spoken, though there may be remarkable exceptions such as a very clear (and useful!) 'no'. Examples of this lack of clarity might include 'ball' being pronounced as 'or' and 'knee' being pronounced as 'dee'.

   2. Speech errors affect vowels as well as consonants. For instance, 'milk' might be pronounced 'mih', 'muh' or 'meh'.

   3. Inconsistency is evident, with the same word being pronounced in several different ways (e.g., 'me' pronounced as 'ee', 'dee', 'bee' 'nee', or 'mee'). This is called token-to-token variability.

   4. Sounds that are used in some words are omitted from other words. I knew a child who could say 'p' TWICE in the word 'Poppi' (her grandfather) but who pronounced both 'happy' and 'puppy' as 'huh-ee'.

   5. When asked to imitate speech sounds, sound effects (e.g., car noises: brm-brm etc) or words, the child does not seem to know where to start.

   6. They may have unusual intonation, pausing and stress patterns.

   7. They may not seem to know where to "put" nasal resonance.
       

5. Many of these children can UNDERSTAND LANGUAGE at a more advanced level than their limited speech would suggest. This is sometimes called the Receptive-Expressive gap.

6. They MAY not be able to easily copy mouth movements (i.e., non-speech movements) as well as their age-peers, and they may be (understandably!) reluctant to imitate speech movements and words.

Why is it referred to as a 'controversial' diagnosis?
Having said that CAS or sCAS is a motor speech disorder, it is important to note that it is a somewhat controversial diagnosis, with some authorities seeing it as a purely motor speech disorder with no 'language' (linguistic) component; others seeing it as a linguistically based disorder; others seeing it as a combination of these two; with yet another group doubting its very existence as a diagnostic entity!

What do you think?
My own position is that childhood apraxia of speech does exist, as a complex disorder and that no two children with it will be precisely the same. It can range from mild to severe. 

Some children with CAS appear to have a motor planning / programming problem with little or no accompanying language component. In my clinical experience this is a rarity. Most appear to have a motor planning / programming difficulty combined with associated linguistic difficulties, particularly phonological problems and difficulties with expressive grammar and syntax. I do not see these language difficulties as part of the CAS, but as difficulties that commonly occur alongside the CAS.

While the idea of a purely linguistic, or phonological basis (that is, no motor planning component) for DVD is intriguing, to date there is no convincing research data to support such a view.

When can a developmental dyspraxia diagnosis be made?
There is no actual AGE at which CAS can be diagnosed for sure. It is more to do with STAGE than age.

SLP's often have CAS on their 'short-list' of probable diagnoses for children who are late talkers with difficult-to-understand-speech (especially if they have feeding difficulties and sensory integration issues too) but we cannot be really sure until the child has plenty to say, or, at the very least, is making many speech attempts.

Ideally, the SLP has to be in a position to do a detailed speech and language assessment that includes analysing speech movements, speech sounds, speech patterns and speech rhythms. To be able to do this the child has to be attempting to say lots of words.

SLP colleagues and I have made diagnoses of CAS in children who had vocabularies of between 100 and 200 words, and who ranged in age from 2;3 to 4;6. We also know of several children for whom a clear diagnosis of DAS was not possible until after the age of 7.

The Dysarthrias

What is dysarthria?
The question should really be 'What are the dysarthrias?' as dysarthrias have many causes and characteristics. Children with the various types of dysarthria have a neuromuscular impairment. That is, the speech mechanism (larynx, lips, tongue, palate and jaw) may be paralysed, weak or poorly co-ordinated. 

Dysarthrias can affect ALL motor speech processes: breathing, producing sounds in the larynx, articulation, resonance, and the 'prosody' or rhythm of speech.

Can phonetic disorders, phonological disorders, dyspraxia and the dysarthrias co-occur?
The disorders can occur, in varying degrees, in the same individual. For example, a child might have a severe developmental phonological disorder with mild dyspraxic features. Another child might have dyspraxia with mild dysarthria.

Can speech sound disorders occur with OTHER communication disorders?
Specific language impairment (SLI), semantic-pragmatic language disorder (SPLD), stuttering, voice disorders and other communication disorders can occur in the same child, alongside phonological disorders, dyspraxia and dysarthria.

Internet Information about CAS
There is a lot of information on the Internet relating to CAS. Some of it, for example the material on the Apraxia-Kids site with its well moderated listserv, is helpful, authoritative and factual. Unfortunately, the same cannot be said about some of the other sites that are "out there".  Be selective in what you take the time to read or print out, and ask your child's Speech-Language Pathologist (or a SLP colleague if you are a professional seeking information) which sites they recommend. When you visit a site, check for yourself that the author has reliable credentials.

When seeking out information about Childhood Apraxia of Speech in the Internet,  proceed with caution, because not everyone who claims to be a speech and language expert is! 

Handout
INFORMATION FOR FAMILIES
Childhood Apraxia of Speech

If this is all new to you...
Above all, if you are the parent of a child who is in the process of diagnosis, or who has recently been diagnosed with CAS, get on with the therapy and try not to jump ahead in time, worrying about symptoms and situations that may never arise for your child! And please be guided by the SLP who knows your child as he or she is the person who is most likely to be able to provide you with really relevant (even if sometimes uncomfortable) answers.

Electronic discussion
Participate in professional discussion of the issues raised in this article on the phonologicaltherapy list.

Page updated 04 Feb 2010

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