Speech Perception and Persistent Speech Errors

Jon Preston is in my opinion the most interesting researcher to watch in the field of speech sound disorders. His recent studies on structural and functional brain differences in older children with persistent speech errors are very interesting. The two studies complement each other and point to structural and functional differences in supra superior temporal gyrus, consistent with repeated findings of perceptual deficits in children with speech deficits. Additional differences in supramarginal gyrus implicate integration of auditory and somatosensory information during feedback processes that are important for learning to produce speech sounds as well as monitoring and fine-tuning speech sound production as the articulatory system matures.

Given these neuroimaging findings, it makes sense to look for behavioral indices of perceptual difficulties in this population of children with persistent speech sound errors. Recently Preston et al (2015) used SAILS to do this with two different groups of school aged children. SAILS is a tool that I developed for speech therapy with preschoolers. Each module consists of natural speech recordings of adults and children producing a word that begins with a commonly misarticulated phoneme, for example, the word “rat”. Half the words are produced correctly and the remainder are misarticulated, e.g., [wæt], [jæt], [ɹ̮æt]. Each module is designed as a series of blocks in which the contrasts are theoretically closer, e.g., practice [ɹæt] versus [mæt], block 1 [ɹæt] versus [wæt], [jæt] and block 2 [ɹæt] versus [ɹ̮æt].  The child’s task is to identify the words that are “good” representatives of the target word. Although the blocks are numbered, they do not necessarily fall into a linear difficulty scale because each child can be quite idiosyncratic in terms of the features that they attend to. I’ll come back to this point later. After establishing that the tool was effective as an intervention for improving children’s speech perception and speech production skills, I found that it also had some value as an assessment tool (Rvachew & Grawburg, 2006) although I do not feel that the psychometric qualities are particularly good and I certainly did not design it for that purpose.

Now, back to Jon Preston’s study. In the first study, older children with [ɹ] distortions were compared to children with correctly produced [ɹ] and no history of speech delay. They were administered only the “most difficult” levels of SAILS modules including the [ɹ] Level 2 module. Although 1/20 children with typical speech and 6/27 misarticulators failed the [ɹ] SAILS module, the mean difference between groups was not significant. In the second study, a group of 25 children who received speech therapy as preschoolers was tested with SAILS, 3 years later when the speech deficit was resolved except in some cases for a persistent speech sound distortion. Performance on the “most difficult” [s] or [ɹ] module was correlated with their performance on an [s] or [ɹ] production probe. There was no correlation. (I was initially mystified by the perception results because they didn’t look like anything I had seen before but that was before I realized that the children were not presented with the complete test!).

So, how do we interpret these results? I have three comments.

First, Preston, Irwin, & Turcios have done us all a good turn by establishing that SAILS is NOT a good tool for assessing speech perception in 7 to 14 year old children with persistent speech errors. I never intended it for that purpose and I am pleased to have empirical evidence that supports a clear answer to the question when it comes up (we should be grateful to Seminars in Speech and Language for publishing it I suppose, despite the small samples, because rumour has it that ‘negative results’ are hard to publish). Anyway, we need something better for testing speech perception, especially for older children. I invite reader comments on what that “something better” would be. We know from many studies using synthetic speech that this population is at risk for perceptual deficits. We need to be able to identify those children in the clinic.

Second, if you are going to use SAILS for assessment (with children aged 4 to 7) it is very important to administer the complete module to the child, working through all the levels of the module, in order as intended. We cannot be sure that the child’s response to, for example Level 3 /s/, will mirror that of the normative samples who encountered Level 3 after first working through Practice, Level 1 and Level 2 before getting there. I will come back to this in another post in which I will give a sneak peek at the upcoming second edition of our book Developmental Phonological Disorders: Foundations of Clinical Practice.

Third, the relationship between speech perception and speech production is not linear. Even though I have found relationships between speech perception and speech production in the past using some rather fancy statistics with large groups (Rvachew & Grawburg, 2007; Rvachew, 2006), I cannot at the individual child level relate in a simple fashion SAILS score with number of correct productions of a phoneme. The reason is that the child’s production and perception of a phoneme is related to the way in which the child attends to the features associated with phoneme contrasts and certain features have different information value for perception versus production. We give an example of this in Chapter 4 of DPD (from Alyssa Ohberg’s masters thesis): preschoolers who were stimulable for /θ/ and /s/ but had not mastered this contrast were administered the SAILS /θ/ assessment module. Some children, in their speech, differentiated /s/-/θ/ by manipulating the duration cue whereas others differentiated /s/-/θ/ by manipulating the spectral cue; as you would expect, manipulating the spectral cue resulted in comparatively better articulatory accuracy but these two groups produced roughly comparable perceptual performance but with some interesting differences. The children who attended to the spectral cue actually did better on the supposedly “harder” level 3 stimuli than the supposedly “easier” level 2 stimuli, highlighting again that there is not a linear difficulty gradient across the stimulus blocks. The children who attended to the duration cue did surprisingly well at levels 2 and 3.  For some stimuli, attention to the duration cue actually provides an advantage. This results occurs because duration is actually a pretty reliable cue for perception of /θ/ but it does not provide any information that helps the child achieve the critical articulatory gestures (e.g., grooved versus nongrooved tongue,interdental versus alveolar tongue tip placement). In this case, there is no direct linear relationship between the child’s speech perception score and their speech production score on the tests that we gave. However, there is a direct relation between the child’s perceptual focus on only one of the relevant acoustic cues and their inability to produce the phoneme correctly. The only children who achieved good perception scores and good production scores attended to both the duration and the centroid cues.

This example raises a fourth point and that is, drawing on Shuster’s findings, the best test for older children may well involve using the child’s own speech production output. The most important question is, does the child mistakenly believe that their own productions are accurate and acceptable representations of the target category? I cannot recommend Shuster’s brilliant study highly enough for anyone treating this population. If the child does prove to have incomplete perceptual knowledge of /ɹ/ or /s/ however, treatment that includes highly variable (multi-talker) stimuli remains important, as a general rule of perceptual learning.

Further Reading

Preston, J. L., Felsenfeld, S., Frost, S. J., Mencl, W. E., Fulbright, R. K., Grigorenko, E. L., . . . Pugh, K. R. (2012). Functional Brain Activation Differences in School-Age Children With Speech Sound Errors: Speech and Print Processing. Journal of Speech, Language, and Hearing Research, 55(4), 1068-1082. doi: 10.1044/1092-4388(2011/11-0056)

Preston, J. L., Molfese, P. J., Mencl, W. E., Frost, S. J., Hoeft, F., Fulbright, R. K., … & Pugh, K. R. (2014). Structural brain differences in school-age children with residual speech sound errors. Brain and Language, 128(1), 25-33.

Preston, J. L., Irwin, J. R., & Turcios, J. (2015). Perception of Speech Sounds in School-Aged Children with Speech Sound Disorders. Seminars in Speech and Language, 36(04), 224-233. doi: 10.1055/s-0035-1562906

Rvachew, S. (2006). Longitudinal prediction of implicit phonological awareness skills. American Journal of Speech-Language Pathology, 15, 165-176.

Rvachew, S., & Grawburg, M. (2006). Correlates of phonological awareness in preschoolers with speech sound disorders. Journal of Speech, Language, and Hearing Research, 49, 74-87.

Shuster, L. I. (1998). The perception of correctly and incorrectly produced /r/. Journal of Speech, Language, and Hearing Research, 41, 941-950.

 

 

 

 

 

 

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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.

How should we describe substitutions in phonology?

I have just read the very nice paper by Little, Bernhardt & Payne (2014) in the open-access journal CJSLPA. It contains a very nice description of nonlinear phonology followed by an analysis of the speech produced by a child with a rare metabolic condition called “3-methylglutaconic aciduria type I”. I liked the early part of the paper in which the authors discuss nonlinear phonology from two perspectives, optimality theory versus a connectionist modeling approach, because personally I find OT to be a waste of time because it is my opinion that this model is not biologically plausible whereas connectionist modeling (depending on the model of course) can often do a pretty decent job of simulating developmental processes. So I found that part to be interesting. As for the latter part of the paper, I got a bit hung up in the details unfortunately, and one detail in particular was crazy making: The authors described the substitution errors like this:  “Fricatives were deleted or substituted with stops or other fricatives; /ɹ/ was deleted or substituted with [w] (onset), or with a vowel (coda)” (p. 289).

If you are younger than me this may not strike you as strange but it was to me so odd I looked it up and I found a discussion about the usage of the word “substituted” on the on-line Oxford Dictionary which says that the traditional form is “A was substituted for B” but that due to frequent use by sports commentators the form “B was substituted with A” is currently  accepted usage despite the fact that “this can be confusing” (no kidding!). Apparently in chemistry it is common to say “B was substituted by A” which is a form my students in Quebec will use which has always confused the heck out of me.

In phonology, the confusion is particularly acute because of the use of the short form A/B  in both informal and formal written reports to describe children’s speech errors. Recently I was interacting with an SLP who was asking for advice about a child and she described the child’s errors as t/k, d/g. Confusion reigned until it was established that the child’s pattern was backing and not fronting!

So it looks to me that if we have a child who says “keep” /kip/ = [tip], we now have alternative forms of communicating this in the SLP community:

Old fogie way:

  • Long form: The child substituted [t] for /k/.
  • Short form: t/k substitution

New fangled way:

  • Long form: The child substituted /k/ with [t]. (The child substituted /k/ by [t].)
  • Short form: k/t substitution

This means that we have a serious problem with confusion in written reports when the short form is used. In oral reporting there is still a risk of confusion because we do not typically transmit the square brackets and slashes when we are speaking.

So, solutions, anyone?