What is the difference between an articulation disorder and a phonological disorder?

Questions from parents

Our four year old has a speech disorder and the speech therapist says it is not an articulation disorder but a phonological disorder. What is the difference between an articulation disorder and a phonological disorder? How can you tell the difference? Are they treated differently?

A question from a colleague in the US

Although I have been a school-based SLP for over 20 years I have to say I am confused about the distinction between phonetic speech sound disorders (artic disorders), and phonemic speech sound disorders (phonological disorders). In simple terms, what exactly is the difference?

Explanation

Before we can understand the distinction between an articulation disorder and a phonological disorder we need to look at what is meant when SLPs/SLTs talk about 'speech' and 'language'.

Speech

Speech is the spoken medium of language. Speech has a phonetic level and a phonological (or phonemic) level.

Phonetic (articulation) level

The phonetic level takes care of the motor act of producing the vowels and consonants, so that we have a repertoire all the sounds we need in order to speak our language(s).

Phonological (phonemic) level

The phonological or phonemic level is in charge of the brainwork that goes into organising the speech sounds into patterns of sound contrasts. The sounds need to contrast with each other, or be distinct from one another, so that we can make sense when we talk.

Articulation (phonetic) disorder

In essence, an articulation disorder is a SPEECH disorder that affects the PHONETIC level. The child has difficulty saying particular consonants and vowels. The reason for this may be unknown (e.g., children with functional speech disorders who do NOT have serious problems with muscle function); or the reason may be known (e.g., children with dysarthria who DO have serious problems with muscle function).

Typical speech development

Speech-Language Pathologists / Speech and Language Therapists (SLPs/SLTs) make a detailed study of all aspects of normal human communication and its development in the areas of voice, speech, language, fluency and pragmatics. A thorough knowledge and understanding of what science reveals about typical speech development is critical to our understanding of children's speech sound disorders

Language

Language has been called the symbolisation of thought. It is a learned code, or system of rules that enables us to communicate ideas and express wants and needs. Reading, writing, gesturing and speaking are all forms of language. Language falls into two main divisions: receptive language (understanding what is said, written or signed); and, expressive language (speaking, writing or signing).

Phonological disorder

A phonological disorder is a LANGUAGE disorder that affects the PHONOLOGICAL (phonemic) level. The child has difficulty organising their speech sounds into a system of sound contrasts (phonemic contrasts). 

How do articulation disorder and phonological disorder differ?

In an articulation disorder the child's difficulty is at a phonetic level. That is, they have trouble making the individual speech sounds (even though there is nothing 'wrong' with their articulators).

In a phonological disorder the child's difficulty is at a phonemic level (in the mind). This "phonemic level" is sometimes referred to as "the linguistic level" or "a cognitive level".

Co-occurrence

An articulation disorder and a phonological disorder can co-occur. That is, the same child can have BOTH.

Assessment and diagnosis

Because of their knowledge-base, SLPs/SLTs are able to distinguish between the many speech and language disorders they have to assess (or "differentially diagnose") in the course of their work. 

The assessment process typically involve screening the child's communication skills in a general way, and then forming an hypothesis about the nature of any apparent difficulties. 

If speech clarity is a problem the SLP/SLT will examine both the PHONETIC and the PHONOLOGICAL aspects of the child's speech. The tests chosen will depend on the child's presentation and the theoretical orientation of the clinician.

Use of terminology

Some SLPs/SLTs use the term "articulation disorder" very loosely, especially when they are explaining these complex ideas to people who do not have a background in linguistics or speech pathology. Indeed, they may refer to a "phonological disorder" as an "articulation disorder". 

It can often be quite helpful for parents to ask their SLP/SLT what they mean by the particular terms they use.

"Functional"?

The term "'functional" speech disorder' is usually equated with the concept of "cause unknown" and these disorders are often referred to as speech disorders of unknown origin. 

Although we cannot "prove" or "demonstrate" what has "caused" a speech sound disorder in a particular child, we can often form justifiable hypotheses regarding the likely cause, given a child's history (Flipsen, 2002). Factors such as family history, frequent otitis media, childhood apraxia of speech, and psychosocial factors (Shriberg, 1993) may be considered.

"Developmental"?

The word "developmental" in "developmental phonological disorders", "developmental dysarthria", and "developmental verbal dyspraxia" (this is the preferred term in the UK; the preferred term elsewhere is "childhood apraxia of speech") simply denotes that the disorders occur in children. The word "developmental" is not appended to functional speech disorders, which occur in both children and adults.

Discussion

The phonologicaltherapy discussion group provides communication disorders professionals with an opportunity to ask and answer questions and explore theoretical and research issues related to children's speech sound disorders in general, and phonological disorders, articulation disorders, and childhood apraxia of speech in particular.

The emphasis in discussions is on theoretically sound, evidence-based clinical assessment and intervention.

References

Flipsen, P. Jr. (2002, May).  Causes and speech sound disorders. Why worry?  Presentation at the Speech Pathology Australia National Conference: Alice Springs, Northern Territory, Australia.

Shriberg, L.D. (1993). Four new speech and prosody-voice measures for genetics research and other studies in developmental phonological disorders. Journal of Speech and Hearing Research, 36, 105-140.