Cross-linguistic perspective on “atypical” error patterns

As a clinical phonology instructor working in a linguistically and culturally diverse environment I am conscious of the need to prepare my students for clinical practice with children who may speak languages that are not English. I am forced to narrow my focus in the classroom to English normative data because there is only so much time and because most of the available clinical data pertains to English. At the same time I know that those students who plan to practice in English-dominant environments will have some bilingual children on their caseloads. That part of my class that plans to stay in Montreal will be working in a bilingual environment, switching hourly between English dominant and French dominant patients who often know a second or third language. Finally a good proportion of the class are international students who plan to return to their home countries to practice in a language that is neither English nor French. Therefore the question of how best to ensure that they have analytical tools and background knowledge that will allow them to apply what they have learned in an English context to other languages is paramount. Sharynne McLeod’s work and the Multilingual Children’s Speech website  is enormously important in this regard.

I really enjoyed the systematic review by Hambly, Wren, McLeod and Roulstone on “the influence of bilingualism on speech production”. I especially liked the introductory summary of Stackhouse and Wells’ psycholinguistic model whereby phonological development is “simplified into three phases: input → storage → output”. This model figures prominently in our book and was one influence on the organization of our discussion of treatment procedures in Part III. In their review, Hambly et al. describe many papers that recount instances of apparently atypical error patterns in bilingual children with typical or atypical speech development. Many of these patterns reflect transfer from one language to another such as unexpected voicing patterns, trills or spirants crossing over from first language Punjabi, Russian or Spanish to second-language English. The papers reviewed also described patterns that were rare across languages however: for example, the rare occurrence of backing in a variety of first and second language contexts lead some authors to the conclusion that backing is universally rare and therefore always atypical. Francoise and I are aware of a context in which an error pattern that might be mistaken for backing is not rare however. Our papers describing typical and atypical French phonology take a multilinear and multirepresentational approach and highlight the disconnect between the persistence of a phonological pattern approach to the description of children’s speech despite the important insights offered by the psycholinguistic approach to phonological development.

Although the theoretical underpinnings of phonological processes are not necessarily implied when clinicians and researchers speak of phonological patterns I think that it is helpful to recall the theoretical roots of this approach. The original idea was that the child’s underlying representations were adultlike even though the child’s motor abilities were not up to the task of producing speech that matched adult expectations. Therefore one assumed that the child’s underlying representation for a word such as “cone” would be /kon/ but an innate simplification process would front the /k/, leading to [ton]* in the output. The error pattern in “cone” → [ton]*, “key” → [ti]*, “cake” → [tet]* is called velar fronting, implying that an underlying present velar is fronted during the transition to the output form. The opposite pattern, in which a front sound, e.g., /t, d, s, z/ is produced as a back sound, e.g., /k,ɡ,ʃ,ʒ /, is referred to as backing but is atypical by virtue of infrequence. I am not going to recount all of the evidence against this position here but suffice it to say if it doesn’t work for phonological development in the case of a child learning one language according to a typical trajectory it is even less tenable as an explanation for mismatches in bilingual children’s speech and it is clearly not tenable as an explanation for mismatches in the speech of children with a phonological disorder.

Continuing with the example of backing I am going to show that this is a poor description of apparent backing errors in English or French speaking children with a phonological disorder. In English speaking children, backing alveolar consonants is indeed rare and thus termed “atypical”. The atypical nature of the error is further enhanced by the phonological problem that it represents: when analyzed from a multilinear perspective, fronting means that the child is using the default Coronal feature or is delinking the marked Dorsal feature, resulting in a simplification; on the other hand, backing is in most contexts phonologically impossible since it involves adding a marked feature unless the child has a very unusual phonological system in which Dorsal is the default place feature. How then does the error arise? Answering this question requires that one examine the articulatory roots of the child’s problem as was done by Fiona Gibbon in her description of “Undifferentiated Lingual Gestures in Children with Articulatory/Phonological Disorders.” Electropalatography shows that this error pattern is rooted in an abnormal lingual gesture during speech that is pervasive, affecting all the lingual phonemes and often resulting in other atypical errors such as lateral distortions of sibilants. One thing that is important and interesting about the child’s error pattern is that it is revealed to be not backing of front sounds at all since all the lingual phones are produced with a similarly undifferentiated gesture (neither front nor back but whole tongue dorsum in contact with the palate); the listener’s percept of a front or back sound is determined by the timing of the release phase of the gesture. In this case, in English, the error is a highly atypical error reflecting a motor speech problem that is not accurately described as backing.

Now, turning to French, we have published raw data from francophone children with a phonological disorder in the Canadian Journal of Speech-Language Pathology and Audiology: we have observed that in both typical and atypical development it is very common for French speaking children to substitute a back sound for a front sound in a very particular context, specifically the /ʁ/-clusters. We show first of all that the output form [kʁ] is easiest for the children to acquire and thus the place features of the two consonants appear to facilitate production of each other, e.g., as in ‘crayon’ /kʁɛjɔ̃/ → [kʁɛjɔ̃]. Second, in the case of /tʁ/-clusters, spreading of place from the /ʁ/ to the unspecified place node on the /t/ is very common resulting in an apparent backing error, e.g., as in ‘train’ /tʁɛ̃/ → [kʁɛ̃]*. Interestingly, we see the spreading of the Dorsal feature from the second segment in the cluster back to the first segment of the cluster even when the /ʁ/ target is produced as [w] and in the case of /w/ clusters (recall that this phone has both labial and dorsal place features), e.g., “doigt” /dwa/ → [ɡwa]*. Finally, we observe even more unusual productions such as, ‘framboise’ /fʁɑ̃bwaz/ → [kwɑ̃bjaz]*, suggesting that the features of /f/ are difficult for the child to capture perceptually in these words, perhaps resulting in substitution of a preferred form in the complex onset. We have seen similar error patterns in the speech of francophone children with typically developing speech. The conclusion to be drawn in the case of French is that this error is not a backing error at all; it is a spreading error that makes perfect sense in its typical context. In this case it is not atypical, neither from the perspective of its frequency nor from the perspective of its phonological origins.

I have shown that an error pattern that may look similar on the surface can have a very different origin in two languages and thus be atypical in one and typical in the other. My overall conclusion from this discussion only partly echoes that made by Hambly et al: it is true that SLPs need more information about how phonology develops in children who are learning different languages and multiple languages. However it is even more important for SLPs to have the analytical tools to describe children’s phonology at multiple levels of representation (perceptual, articulatory, phonological) and to identify the origin of children’s error patterns after taking all these domains of phonological learning into account.

Further Reading

If you are not familiar with multilinear phonology, here is a source  intended for a clinical audience:
Bernhardt, B., & Stoel-Gammon, C. (1994). Nonlinear phonology: Introduction and clinical application. Journal of Speech and Hearing Research, 37, 123-143.

For another example of “backing” that is typical in another language, see:
Li, F., Edwards, J., & Beckman, M. E. (2009). Contrast and covert contrast: The phonetic development of voiceless sibilant fricatives in English and Japanese toddlers. Journal of Phonetics, 37(1), 111-124.

For our complete multirepresentational explanation of francophone children’s cluster productions, ask us for a copy of this manuscript:
Rvachew, S. & Brosseau-Lapre, F. (accepted with minor revisions). Pre- and post-treatment production of syllable initial /ʁ/-clusters by French-speaking children. In M. Yavas (Ed.), Unusual productions in phonology: universals and language-specific considerations. Psychology Press/Taylor Francis.

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  1. I have had a conversation with a very special reader of my blog who reminds me that there is another context in which backing of coronal stops and fricatives is likely to occur: specifically, this pattern of speech production error may be a marker for speech delay associated with chronic otitis media with effusion, as described in Shriberg, L. D., Kent, R. D., Karlsson, H. B., McSweeny, J. L., Nadler, C. J., & Brown, R. L. (2003). A diagnostic marker for speech delay associated with otitis media with effusion: backing of obstruents. Clinical Linguistics & Phonetics, 17, 529–547. The stops and the fricatives are cued in part by the first spectral moment (centroid frequency peak) of the noise either in the burst or the fricative portion of the segment. Otitis media will make it difficult to identify the relevant cues. Some children with these errors have been shown to manipulate nonstandard acoustic cues to these phoneme contrasts (e.g., ‘k’ vs ‘t’ or ‘sh’ vs ‘s’) in their speech, perhaps relying on those cues that are easier to hear. In turn these errors can be associated with parallel perceptual confusions. So I was wrong to suggest that all cases of backing error are motoric in origin. This is another case however in which it is important to consider the phonetic and phonological underpinnings of the child’s error pattern and in which the child’s underlying knowledge is not adultlike. I am very pleased to be reminded to of this other possibility. How would the SLP identify OME related backing versus ULG without access to electropalatography? I am not sure. One major difference between Shriberg’s sample and Gibbon’s sample is age with the mean age of the children being much younger in the former study. In Gibbon’s study some of the children who backed velars and sibilants had ULGs and some didn’t; both groups (those with and those without ULGs) had some children who backed the sibilants and some who lateralized them. I believe that accurate auditory feedback is required to learn accurate lingual gestures however and that phonological knowledge emerges from experience at the intersection of both domains. Possibly ULGs might themselves arise from perceptual deficits in some cases and motoric deficits in others. In any case, we must attend to both perceptual and articulatory knowledge in our treatment programs.

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