What’s in a Name? Does SSD Smell Sweeter than DPD?

Francoise and I are engaged in the writing of two books currently. I am taking the lead on the revision (mostly cosmetic) of Developmental Phonological Disorders: Foundations of Clinical Practice (the “big book” that we call DPD for short) while Francoise is taking the lead on the writing of a new undergraduate text that will prepare readers to tackle the “big book” at the graduate level or to use the DPD text as a handbook in clinical practice. We still haven’t figured out what to call the second book! Introduction to Speech Sound Disorders? Introduction to Developmental Phonological Disorders? Introduction to Articulation and Phonological Disorders? Some combination of the above? We notice that many of the undergraduate text books now have very long titles because the authors keep adding terms as they become “fashionable”. I have just arrived (in my revising) at the introduction to Part II of the DPD text in which we explain our preference for the term Developmental Phonological Disorders. Even though this text is copyrighted to Plural Publishing Ltd. I am going to reproduce it here in case any of my readers would like to weigh in. We have been told that instructors cannot use the big DPD text because it is not titled with the preferred American term ‘speech sound disorders’ and I have met readers who were very surprised to learn that we covered articulation disorders and motor speech disorders in the book, as if the children with these problems did not have developing phonological systems! So much complexity here – I look forward to your thoughts in the comments or on twitter or by email. Here is the text from our book, Part II Introduction:

Developmental Phonological Disorders as the Diagnostic Term

As we discuss the application of the ICF framework in the context of DPD, we must be begin by unpacking the term “developmental phonological disorder” and justifying this choice of terminology to describe this health condition. Since the dawn of our profession, many terms have been used to describe children who have unintelligible or inaccurate speech, with all of the terms reflecting the tongue-in-cheek perspective of Compton (1970) who compared the diagnostic role of the SLP to that of a “TV repairman”! The diagnostic term that is applied specifies the “part” that is presumed to need fixing, either “articulation,” “phonology,” or “speech,” with these terms all in current use although, historically, earlier usages focused on articulation problems and current preference in North America is to refer to “speech” as a cover term that is presumed to include both the articulatory and phonological aspects of the child’s difficulty. We feel, however, that “speech” is too broad a term because it is often used as a cover term for difficulties with articulation, stuttering and voice in epidemiological studies, as seen in Chapter 7. Furthermore, in the developmental context there is no possibility of separating articulation from other aspects of phonological knowledge. Children who appear to have a motor speech problem called childhood apraxia of speech have significant difficulties with various aspects of phonological processing (see Chapter 7 for further discussion of this point). Returning to the topic of cleft lip and/or palate, this structural disorder that might appear at first glance to cause a purely articulatory problem, actually results in speech patterns that are best described and treated with phonological approaches (Howard, 1993; Pamplona, Ysunza, & Espinoza, 1999). Therefore, it is our preference to identify the central issue as being in the child’s developing phonological system, stressing as we do throughout this book, that phonology comprises interlocking components at multiple levels of representation.

The diagnostic term also requires one or more modifiers that indicate a specific type of phonological problem. We use the term “developmental” to simply denote that we are referring to children whose phonological systems are still developing. Furthermore, as shown in Chapter 7, the most likely causal factors in the majority of cases are interacting genetic and environmental variables that impact primary neurodevelopmental processes. The modifier “functional” was used for many decades, sometimes replaced with the phrase “of unknown origin,” to differentiate problems that had a known biological cause from those that did not and were therefore presumed to reflect an unexplained failure to learn the required articulatory gestures or an unexplained delay in the suppression of phonological processes. We reject these terms on the grounds that distinguishing between biological causes that are currently known and those yet to be discovered is nonsensical and that, furthermore, we cannot force a pure demarcation between biological and environmental causes. For example, so-called functional speech problems are indeed associated with sociodemographic disadvantages (for discussion, see Shriberg, Tomblin, & McSweeny, 1999) but these sociodemographic conditions are themselves associated with biological causal-correlates such as increased risk of otitis media, fetal and child exposure to parental smoking, and low birth weight. Furthermore, environmental variables and biological maturation are reciprocally related as discussed in Part I: maturation of brain function in areas associated with language and reading development is driven in part by exposure to high quality language input. In another example, Noble, Wolmetz, Ochs, Farah, and McCandliss (2006) demonstrated that socioeconomic status significantly moderates the relationship between brain function and phonological processing even when phonological abilities are controlled across advantaged and disadvantaged groups. The nature of the relationship is such that high quality inputs for children in advantaged homes buffers them from the ill effects of poor phonological processing abilities, allowing them to achieve higher reading levels and higher activations in areas of the brain important to reading than would be predicted on the basis of their phonological processing abilities alone. Disadvantaged children show a correspondence between brain activation and reading ability that is linearly predicted by their phonological processing skills, however. These kinds of studies support a dynamic systems approach to phonological disorders and highlight the joint causal influences of intrinsic and extrinsic factors on children’s linguistic functioning (issues that are revisited in Chapter 7 when we discuss approaches to the subtyping of phonological disorders). For these reasons we prefer the modifier “developmental” rather than “functional” or any other term that strictly demarcates biological and nonbiological causes of phonological difficulties.

Finally, there continues to be some controversy about whether the problem should be referred to as a “disorder” or a “delay.” In fact, as we discuss further in Chapter 7, some classification systems explicitly differentiate between children whose speech appears to be delayed by virtue of having characteristics similar to younger normally developing children and those whose speech has characteristics deemed to be atypical. We argue as we move through Part II that the diagnostic and prognostic implications of this distinction are uncertain and that the delay-disorder classification exists more on a continuum of severity than a sharply delineated categorical distinction. With respect to those children who are deemed to have a “disorder” on the basis of “atypical” speech errors or learning processes, it is our impression that the child’s behaviors are only “atypical” in the context of the child’s age or overall profile. For example, inconsistent word productions are often considered to be atypical and yet we showed in Chapter 4 that variable word productions are fully expected in the earliest stages of word learning. Therefore atypical behaviors reflect heterochronicity in developmental trajectories across cognitive-linguistic domains within a child rather than fundamentally different learning processes across children. As to those children who appear to have typical but delayed patterns of speech error, we take the position that some children’s delay is severe enough that it places them at risk for current or future activity limitations and participation restrictions. Consistent with the position of the ICF-CY (McLeod & Threats, 2008), the problem in this case deserves the appellation “disorder”. Furthermore, to be consistent with the dictionary definition of the word “disorder”, this appellation justifies an intervention to change the child’s rate or course of development so as to synchronize function among different developmental domains or to align function with expectations for activities and participation.

Ultimately, this brings us to the diagnostic term developmental phonological disorder (DPD), which corresponds to one of the superordinate categories in the Speech Disorders Classification System as originally formulated (Shriberg, Austin, Lewis, McSweeny, & Wilson, 1997). DPD can be contrasted with normal (or normalized) speech acquisition, differentiating those children whose speech development is progressing as expected from those children who, at ages younger than 9 years, are producing more speech errors than would be expected for their age. Nondevelopmental phonological disorders denotes those cases where the speech difficulty has its onset after 9 years of age. Speech differences arise from cultural and linguistic diversity and are not considered to be a speech impairment (although a speech difference may overlap with a coexisting health problem and may have functional consequences for an individual’s participation in some environments). The outcome of the initial assessment of a child who is referred due to concerns regarding speech accuracy or intelligibility should be a diagnosis with respect to one of these 4 major categories. Subsequent to an initial diagnosis of DPD the SLP may also diagnose a specific subtype of DPD, as discussed in Chapter 7.

We point out here that throughout Parts II and III we remain focused on those cases where the child’s primary difficulty is with speech (and/or language and/or reading). We do not specifically cover secondary phonological disorders in which the child’s speech delay is directly associated with impairments of sensory systems, cognitive deficits, craniofacial anomalies or other developmental disorders. The assessment and treatment procedures to be described are applicable to children with secondary speech delay with modifications to take these specific developmental conditions into account however.

References

Compton, A. J. (1970). Generative studies of children’s phonological disorders. Journal of Speech and Hearing Disorders, 35(4), 315–339.

Howard, S. J. (1993). Articulatory constraints on a phonological system: A case study of cleft palate speech. Clinical Linguistics and Phonetics, 7, 299–317.

McLeod, S., & Threats, T. T. (2008). The ICF-CY and children with communication disabilities. International Journal of Speech-Language Pathology, 10, 92–109.

Noble, K. G., Wolmetz, M. E., Ochs, L. G., Farah, M. J., & McCandliss, B. (2006). Brain-behavior relationships in reading acquisition are modulated by socioeconomic factors. Developmental Science, 9, 642–654.

Pamplona, M. C., Ysunza, A., & Espinoza, J. (1999). A comparative trial of two modalities of speech intervention for compensatory articulation in cleft palate children: Phonological approach versus articulatory approach. International Journal of Pediatric Otorhinolaryngology, 49, 21–26.

Shriberg, L. D., Austin, D., Lewis, B. A., McSweeny, J. L., & Wilson, D. L. (1997). The Speech Disorders Classification System (SDCS): Extensions and lifespan reference data. Journal of Speech, Language, and Hearing Research, 40(4), 723–740.

Shriberg, L. D., Tomblin, J. B., & McSweeny, J. L. (1999). Prevalence of speech delay in 6-year-old children and comorbidity with language impairment. Journal of Speech, Language, and Hearing Research, 42(6), 1461–1481.

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Using Orthographic Representations in Speech and Language Therapy

Word learning, and in particular, productive word learning is associated with three important processes in the phonological domain: first, the child must encode the acoustic-phonetic form of the word in the language input; second the child must transform this representation into a lexical representation, generally considered to take on a more abstract phonological form; finally the child must retrieve the representation to reproduce it. The first process is reliant on speech processing abilities that have been shown to be impaired in many children with speech, language and reading deficits, as shown by for example by Ben Munson and colleages (@benjyraymunson) and Nina Kraus and colleages. Phonological encoding is enhanced by access to repeated high-quality but variable inputs as shown by Richtmeier et al for normally developing children and by Rice et al for children with SLI. The majority of children with SSD have difficulties with encoding: we have a paper in press with the American Journal of Speech-Language Pathology showing that speech accuracy in these children can be improved with an approach that focuses largely on the provision of intense high quality input – I will have more to say on this subject when it (finally) emerges in print.

The second process, forming a phonological representation and storing it in the lexicon, involves articulatory recoding which can be a serious problem for children with severe SSD, accounting for deficits in speech accuracy (especially in association with inconsistency), nonword repetition, word learning, productive vocabulary, word finding, rapid automatic naming, and other phonological processing skills. These children are often diagnosed with motor planning disorders but I have pointed out previously that the problem is actually at the level of phonological planning. I have further pointed out the very close relationship between speech planning and memory. Children who are having difficulty with phonological planning may not show the same benefit from a therapy approach that is focused on the provision of high quality inputs. Therefore a new paper on the use of orthographic inputs to teach new words caught my eye.  Ricketts et al taught children with SLI and ASD as well as younger and age-matched children with typical language to label nonsense objects with new names, using a computer program. For some words, the children were exposed only to the object–auditory word pairing; for others they saw the object, heard the word and saw a printed version (orthographic representation) as well. All children found it easier to learn the new words when they were exposed to the orthographic representation along with the auditory word.

This study reminded me of the research we are doing with children who are referred to our clinic with an apraxia diagnosis due to inconsistent speech errors. So far, 40% of those children have difficulty with phonological planning rather than motor planning as revealed by the syllable repetition test, as I have explained in a previous blog. We have been using a single subject randomization design to compare the relative efficacy of two treatment approaches with these children. The Phonological Memory & Planning (PMP) intervention pairs the phonemes in the target words with visual referents that include letters as shown here. Imitative models are avoided and the child is encouraged to create their own phonological plan and produce the word using the visual symbols when necessary. An alternative treatment, the Auditory-Motor Integration (AMI) Treatment is quite different with a heavy emphasis on prior auditory stimulation and self-judgments of the match between auditory inputs and outputs. A third condition is a usual care CONtrol condition focusing on high intensity practice. In all cases we teach nonsense words paired with real objects, with the words structured to target the children’s phonological needs in the segmental and prosodic domains.

The results are assessed by applying a resampling test to probe scores and then combining p-values across the children. These are the statistical results (F and t tests by resampling test) for the Same Day Probe Scores, with p-values combined across the 5 children who have proven to have phonological planning problems in concert with a severe inconsistent speech disorder:

TASC PMP results Aug 2015

The results in the third column show that all of the children obtained a significant treatment effect. The findings in the remaining columns pertain to planned comparisons with positive t values being in the expected direction. The combined p values indicate that all treatments are significantly different from each other and inspection of the mean scores across children show that the pattern of results is PMP > CON > AMI. The result is made more interesting by the fact that the pattern of results is the exact opposite for children with a motor planning disorder. Tanya Matthews and I will compare these two subgroups with data and video during our presentation at ASHA 2016 in Denver this coming fall.

Session Number: 1429
Session Title: Differential Diagnosis of Severe Phonological Disorder & Childhood Apraxia of Speech
Day: Friday, November 13, 2015
Time: 1:00 PM – 3:00 PM
Session Format: Seminar 2-hours

For now, the take away message is that learning new words involves (at least) three important processes: encoding the sound of the new word, memory processes for storing and retrieving the phonological representation and motor planning processes for planning and programming articulatory movements prior to production of the new word. There are published studies showing that intervention procedures targeting each of these processes help children with speech, language and reading difficulties. Increasing frequency of high quality input improves quality of the acoustic-phonetic representation. Pairing phonological segments with visual symbols helps with storage and retrieval of the phonological representation. High intensity speech practice with appropriate stimulation and feedback improves motor planning and motor programming. The trick is to figure out which children require which procedures at which time.