Conversations with SLPs (3)

I have had an interesting conversation with some orthophonistes from the Québec community who have their own very excellent blogs, Cuit dans le bec   (Mélissa di Sante and Marie-Pier Gingras) and Langage et cie  (Marie-Pier Gingras). They asked my opinion regarding a debate that arose on their sites and the issue is so interesting that I am replicating my thoughts here, first with English examples and then finishing up with a French example although the evidentiary basis for making diagnostic decisions in the French context is much weaker.

The question that arose was which type of normative data is most appropriate when making decisions about whether a child’s speech is within normal limits or not – age of acquisition norms for segments OR age of suppression norms for phonological processes? The specific example given was the case of a child who misarticulates /f/ – does it matter whether the child stops this fricative (i.e., /f/ → [p]) or makes some other kind of substitution error (e.g., /f/ → [s]). Would this difference in type of error impact on the severity rating for the child’s speech delay?

As it happens I am about to administer the final exam in my fall course on Phonological Development and most of the exam questions will require the students to make exactly this judgment – given a sample of speech from a child of a given age, is the child’s speech within normal limits or not? I teach my students to use and integrate across multiple sources of normative data. It is essential to consider these multiple sources with no one source being more important than any other, specifically: (1) a standardized measure of the total number of errors; (2) phonetic repertoire; (3) segment level age of acquisition norms; (4) phonological process norms; (5) information about atypical versus typical errors; (6) normative data about the development of prosodic structures from a multilinear perspective where available; (7) intelligibility and other “whole word” measures of speech production. In many cases all of these sources of data will line up with each other so that you could use any one and get the same answer but very frequently there are discontinuities between sources of data and therefore you must integrate across these different perspectives and use your clinical judgment. I will provide some examples of cases where the different types of normative perspective do not provide a congruent result.

English Example 1

Male child aged 36 months produces /f/ → [p], /v/ → [b], /s, ʃ, ʧ, θ/ → [t], /z, ʤ, ð/ → [d] and has no fricative sounds in the phonetic repertoire. The Iowa-Nebraska norms indicate that the expected age of mastery for these phonemes is 3;6 for /f/, 5;6 for /v/, and between 7 and 9 years for the remainder. I have known SLPs who would tell parents that there is no need to be concerned about a child like this because the child is younger than the expected age of mastery for all of the phonemes in error but in fact this would be the wrong conclusion – because indeed the type of errors produced by the child does make a difference. We know that a child at the age of 24 months is expected to have fricatives in the phonetic repertoire. Furthermore, stopping of fricatives should be suppressed (occurring with less than 20% frequency) before the age of 30 months.

English Example 2

On the other hand, let’s say we have another male child aged 36 months who produces /f/ → [p] and /v/ → [b] in the word initial position but /f/ → [s] and /v/ → [z] in the word final position;  /s, ʃ, θ,/ → [s] in all word positions and /z, ð/ → [z] in all word positions. Furthermore Percent Consonants Correct in Conversation is 80% and whole word accuracy in conversation is 80%, scores that are within normal limits according to published norms. In this case a conclusion of age appropriate speech could be warranted because the error phonemes are not expected to be mastered at the age of 36 months and the errors are all of the type that are typically observed in children of this age and the stopping that is observed is not pervasive.

English Example 3

A male child produces errors on the following consonant targets on the Goldman-Fristoe Test of Articulation: /k/ (i,m,f), /ɡ/ (i,m,f), /ʃ/ (i,m,f), /ŋ/ (m), /s/ (i,m,f), /z/ (i,m,f), /sl/, /sp/, /st/, /sw/. Fronting of velar stops is pervasive in the child’s speech. In this case, because the child is 5;0 and he has made 20 errors, a percentile rank of 29 is obtained which might suggest that the child’s speech is within normal limits warranting a discharge recommendation except that fronting should be suppressed by age 3 years and fronting in the coda position in particular is atypical. Therefore this child should be eligible for an intervention despite his GFTA score.

English Example 4

Male child age 5 produces errors on the following consonant targets on the Goldman-Fristoe Test of Articulation: /ʃ/ (i), /ʧ/ (i), /ʤ/ (i,m), /l/(f), /r/(i,m), /ɡr/, /kr/, /tr/. These 10 errors would yield a percentile ranking of 48 and the child’s speech could clearly be judged to be within normal limits given that the expected age of mastery is 6 years for the first 4 consonants and 8 years for the /r/. However, what if the child’s speech intelligibility in conversation was found to be only 80%? Then this child would have what is called an intelligibility-speech gap because his consonant accuracy is within normal limits but his connected speech intelligibility is below the expected 100% intelligibility. This gap can be observed in children who have experienced chronic otitis media and may reflect imprecision in the production of consonants and vowels and a reduced vowel space. It is possible that some kind of intervention might be warranted in a case like this.

English Example 5

Male child aged 6 years consistently produces initial and medial /l,r/ → [w] and final /l,r/→ [o]. There are no correct liquids in the child’s repertoire. Here again the difference in normative expectations for phonological processes versus segments must be kept in mind. Mastery of /l,r/ is not expected until ages 7 and 8. However, gliding and vocalization of these liquids is not expected after the age of 5 years. Even a 24 month old child is expected to have a liquid in the phonetic repertoire.  Therefore this child’s speech is concerning even if the GFTA score is within normal limits and the child is younger than the expected age of mastery for these phonemes.

French Example

In French it is very important to take word and phrase structure into account but unfortunately we don’t have as much normative data as we need in order to interpret child performance reliably. We know for example, that when naming simple words, all consonants should be at the level of at least customary production (in fact most are mastered) before age 5 years in French. Therefore if we take the case of the 5 year old male child again, if the child is producing the words “giraffe” → [ziʁas] and “éléfant” → [elesã] then these productions are not age-appropriate. On the other hand, if the child is producing the words “giraffe” → [ʒiʁaf] and “éléfant” → [elefã] then these productions are correct and age-appropriate. What if the child produces the simpler words correctly but says “fromage” → [kʁomaʒ] and “framboise” → [kʁãbwaz]. Surprisingly these strange looking cluster productions might not be concerning in French. Firstly, error frequency is strongly conditioned by syllable stress and position. Therefore, the /f/ targets in “giraffe” → [ʒiʁaf] and “éléfant” → [elefã] are easier because they are in the stressed word-final/phrase-final position. Secondly, the /f/-clusters in French are vulnerable to spreading of the Dorsal feature in /ʁ/ to the initial obstruent, especially in non-final contexts such as this. Although this error is less frequent than simple reduction (e.g., “framboise” → [ʁãbwaz]),  the spreading error occurs with greater than 5% frequency, and is therefore not atypical in French. One thing to keep in mind is that although the segment acquisition norms suggest that consonant acquisition is more or less complete by age 48-53 months, phonological development continues through age 7 years just as in English because mastery requires consistency in the long words that are characteristic of French and in connected speech. French does not have lexical stress per se but phrase level prosody is important. The child may be able to label the picture as ‘fourchette’ but a phrase such as ‘J’ai perdu ma fourchette hier.’  puts the /f/ target in a more difficult context. We need phrase level normative data for French and studies that manipulate syllable complexity, syllable stress and word length variables systematically before we can be really clear about the normal course of phonological development in French. Nonetheless, testing children’s consonant acquisition in the context of words that are consistent with French word structure is important and therefore I would examine Percent Consonants Correct on a screener such as our Test de Dépistage Francophone de Phonologie in addition to considering the segment acquisition norms in MacLeod et al which are based on words with relatively simple structure.

Resources

 In English all of the normative data used in this discussion is available in our book:

Rvachew, S., & Brosseau-Lapré, F. (2012). Developmental Phonological Disorders: Foundations of Clinical Practice. San Diego, CA: Plural Publishing.

 The specific data referred to includes:

Austin, D., & Shriberg, L. D. (1997). Lifespan reference data for ten measures of articulation competence using the speech disorders classification system (SDSC): Waisman Center on Mental Retardation and Human Development, University of Wisconsin-Madison.

Cahill Haelsig, P., & Madison, C. L. (1986). A study of phonological processes exhibited by 3- 4- and 5-year-old children. Language, Speech & Hearing Services in Schools, 17, 107-114.

Schmitt, L. S., Howard, B. H., & Schmitt, J. F. (1983). Conversational speech sampling in the assessment of articulation proficiency. Language, Speech & Hearing Services in Schools, 14, 210-214.

Shriberg, L. D., Flipsen, P., Kwiatkowski, J., & McSweeny, J. L. (2003). A diagnostic marker for speech delay associated with otitis media with effusion: the intelligibility-speech gap. Clinical Linguistics & Phonetics, 17, 507–528.

Smit, A. B. (1993). Phonological error distributions in the Iowa-Nebraska Articulation Norms Project: Consonant singletons. Journal of Speech and Hearing Research, 36, 533-547.

Smit, A. B., Hand, L., Freilinger, J. J., Bernthal, J. E., & Bird, A. (1990). The Iowa articulation norms project and its Nebraska replication. Journal of Speech and Hearing Disorders, 55, 779-798.

Stoel-Gammon, C. (1987). Phonological skills of 2-year-olds. Language, Speech & Hearing Services in Schools, 18, 323-329.

In French the following sources were considered:

Bérubé, D., Bernhardt, B., & Stemberger, J. P. (2013). Un test de phonologie du Français: Construction et utilisation. Canadian Journal of Speech-Language Pathology and Audiology, 37(1), 26-40.

Brosseau-Lapré, F., & Rvachew, S. (2014). Cross-linguistic comparison of speech errors produced by English- and French-speaking preschool age children witih developmental phonological disorders. International Journal of Speech-Language Pathology, Early Online, 1-11.

MacLeod, A. A. N., Sutton, A., Trudeau, N., & Thordardottir, E. (2011). The acquisition of consonants in Québec French: A cross-sectional study of preschool aged children. International Journal of Speech-Language Pathology, 13, 93-109.

Rvachew, S., Leroux, É., & Brosseau-Lapré, F. (2014). Production of word-initial consonant sequences by francophone preschoolers with a developmental phonological disorder. Canadian Journal of Speech-Language Pathology and Audiology, 37, 252-267.

Rvachew, S., Marquis, A., Brosseau-Lapré, F., Paul, M., Royle, P., & Gonnerman, L. M. (2013). Speech articulation performance of francophone children in the early school years: Norming of the Test de Dépistage Francophone de Phonologie. Clinical Linguistics & Phonetics, 27(12), 950-968. doi: doi:10.3109/02699206.2013.830149

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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?