LINGUIST List 26.2999

Tue Jun 23 2015

Review: Neuroling; Phonetics; Psycholing: Miller, Lowit (2014)

Editor for this issue: Sara Couture <saralinguistlist.org>


Date: 12-Jan-2015
From: Chris Plant <chris.plant.speechgmail.com>
Subject: Motor Speech Disorders
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Book announced at http://linguistlist.org/issues/25/25-3203.html

EDITOR: Nick Miller
EDITOR: Anja Lowit
TITLE: Motor Speech Disorders
SUBTITLE: A Cross-Language Perspective
SERIES TITLE: Communication Disorders Across Languages
PUBLISHER: Multilingual Matters
YEAR: 2014

REVIEWER: Chris Plant, Griffith University

Review's Editor: Helen Aristar-Dry

SUMMARY

‘Motor Speech Disorders: A Cross-Language Perspective’ edited by Nick Miller and Anja Lowit is a text that aims to draw attention to a much neglected area of communication disorders. The text is divided into two parts with Part One presenting chapters offering background information to motor speech disorders (MSDs) and concepts applicable to cross-language comparison. Part two then presents overviews of several languages, all of which aim to compare and contrast the focal language with English, which is operationally used as the ‘model language’.

Prior to Part One, Chapter 1, “Introduction”, by Nick Miller and Anja Lowit, sets out to establish the premise and need for such a text. The chapter highlights how much of the established research into assessment, description and treatment of MSDs has been focused on English, particularly American-English speakers and that this has led to theories of motor speech production which may not be universally applicable. This leads Miller and Lowit to state that this ‘narrow perspective’ poses problems when attempting to apply theories regarding assessment and treatment of MSDs beyond the linguistic, social, and cultural confines of English. Such a situation is therefore argued to justify the need for the current volume, which jointly integrates lines of enquiry from speech-language pathology and cross-language comparisons.

Part One: Setting the scene

Part One of the text proceeds with seven chapters, each of which discusses issues that are core to understanding MSDs within a cross-language framework. Each of these chapters will be summarised in turn.

Chapter 2, “Introduction: Cross-language perspectives on motor speech disorders”. by Nick Miller, Anja Lowit and Anja Kuschmann, further lays the foundations for the text as a whole. This chapter sets out the justification for the current volume by claiming only partial truth for the assumption that speech motor control is universal and therefore acquired impairments to speech production, i.e. motor speech disorders, are similarly universal. It is argued that speech production in any language is fundamentally reliant on physiological processes responsible for respiration, phonation/voice, resonance, articulation and prosody. However, different languages possess different sound systems at both the segmental and suprasegmental levels, and crucially, these differences result in different features leading to different contrastive distinctions. Therefore, essentially the same impairment could have very different consequences for speech production in different languages. Several examples are given to illustrate this suggestion. For example, it is suggested that languages with a large number of vowels will be more susceptible to reduction in intelligibility as a consequence of impaired tongue movement, because the positioning required to achieve vowel contrasts will be more fine-grained compared to languages where there are fewer vowels. The chapter proceeds to discuss the seminal research that led to the development of the Mayo classification system of MSDs. While acknowledging the importance of this work, it is also implied that the strict adherence to this system, which was based on American-English listeners rating American-English speakers with MSDs, has been and is continuing to be severely limiting when it comes to broadening the understanding of the manifestation of MSDs in other languages.

Chapter 3, “Motor speech disorders: What are they?”, by Anja Lowit, Nick Miller and Anja Kuschmann, aims to provide a brief background to MSDs for the reader unfamiliar with these forms of communication impairments. This chapter essentially operationalises key terms and discusses each of the constituent terms of the phrase ‘acquired motor speech disorder’. before defining and describing ‘dysarthria’ and ‘apraxia of speech’. This is achieved with reference to current theoretical debates, particularly regarding the basis of apraxia of speech.

Chapter 4, “Motor speech disorders: Issues in assessment and management”, by Anja Kuschmann, Nick Miller and Anja Lowit, provides an overview of issues relating to both assessment and treatment of MSDs. Studies conducted on English-speakers provide the foundation for the discussion with reference to cross-language studies made where applicable. The focus of this chapter is the Diagnostic Intelligibility Testing (DIT) which is a central theme of the entire text. While classic texts in the area of MSDs do advocate the use of intelligibility testing (e.g. Duffy, 2013), the current authors place far greater emphasis on the value of DIT in informing description and diagnosis of the MSD and also in informing treatment. It is discussed how traditional intelligibility assessments often lead to an understanding of the degree of severity in terms of a number, such as a percentage score of intelligibility. Such scores in themselves however do little to aid understanding of how speech is breaking down and therefore how treatment may aim to ameliorate these difficulties. However, DIT is suggested to address these limitations of traditional intelligibility assessments by systematically investigating the speaker’s performance across various sound contrasts in terms of place and manner of articulation and also voicing over a number of trials that allows greater reliability in interpreting exactly which sounds and in which phonetic contexts are particularly problematic. For example, it may be deduced that intelligibility is reduced primarily in bilabial sounds in all word positions and in all phonetic environments and such difficulties may be consistent with observations of reduced lip function. Another key feature of effective DITs is that they will be specifically designed to include items investigating phonetic contrasts relevant within the target language. The authors suggest that there is a general lack of valid and reliable DITs even when it comes to English and then go on to provide principles to guide DIT construction for English and indeed for any language. Suggestions for test construction relate to the development of standardised and phonetically balanced reading passages and also the selection of single words and sentences that are sensitive enough to investigate the speaker’s ability to produce (and the listener’s ability to perceive) “phonologically important contrasts for the language” (p47).

Chapter 5, “Using English as a ‘Model Language’ to understand language processing”, by Michael S. Vitevitch, Kit Ying Chan and Rutherford Goldstein, suggests using English as the ‘Model Language’ when it comes to further cross-language research into MSDs. Primarily this is based on the significant amount of research that already exists for English. However, the chapter is careful to emphasise that while extrapolation of findings in English-speakers may be useful, caution needs to be taken as even minor differences between languages can have very significant repercussions – a point which is emphasised with the analogy that the human genome is 98% identical with that of the chimpanzee. The chapter then reviews key phonological and phonetic/phonotactic properties of English that may especially influence speech production and which may therefore differ across other languages, e.g.,. phonological segments and sequences, syllable frequency and structure, word length, phonological similarity among words, and word frequency, drawing from all manner of psycholinguistic research conducted with healthy speakers and making links to implications for MSDs throughout. The chapter concludes by advocating for further research with healthy speakers from language backgrounds other than English with particular attention to language-specific aspects of phonology and phonetics and their influence on speech production and recognition.

Chapter 6, “Cross-language studies in deaf signers”, by Martha E. Tyrone, begins by presenting a description of the phonological aspects of sign languages with emphasis on American Sign Language and British Sign Language. The phonological variables identified in relation to signed languages include movement, handshape, location, and orientation; and the chapter then goes on to review the research evidence for how dysarthric and apraxic-type disorders manifest to disrupt these dimensions in sign language users with various presenting aetiologies (e.g. stroke, Parkinson’s disease, Progressive Supranuclear Palsy). In general, the manifestations of dysarthria and apraxia in sign language mirror the expectations based on aetiology and lesion location; for instance, signers with cerebellar damage present with uncoordinated sign movements just as speakers with cerebellar damage present with uncoordinated speech movements. It is emphasised that just as with verbal languages, there is a general lack of valid and reliable assessment materials for investigating sign production deficits and also that a body of research needs to develop around plausible treatments.

Chapter 7, “Apraxia of speech in bilingual speakers as a window into the study of bilingual speech motor control”, by Marina Laganaro and Mary Overton Venet, discusses the current challenges to assessment, diagnosis and management of bilingual speakers with apraxia of speech. The chapter takes a psycholinguistic perspective and discusses the suggestion of a mental syllabary at the level of phonetic encoding that acts as a store of frequently produced syllables. The key question addressed throughout the chapter is essentially regarding whether syllabaries are language independent, i.e. that there is one store for each language spoken, or whether a syllabary is shared between languages spoken by the speaker. Through discussion of psycholinguistic research and original data presented based on a pseudoword repetition task with a Swedish-French bilingual speaker, findings are presented whereby it is argued that the combined frequency of syllable production across languages influences task performance. This leads to the conclusion that syllabic motor plans are indeed shared across languages (where they occur in both languages), as opposed to being language-specific.

Chapter 8, “Phonological and speech output in adult non-literate groups”, by Dora Colaço, Ana Mineiro and Alexandre Castro-Caldas, presents a review of key issues related to literacy and the development of phonological awareness (or metaphonological skills). This is done on the premise that assessments that are used to aid differential diagnosis of MSDs frequently involve aspects of metaphonological processing. Initially, the distinction is made between literacy and schooling to emphasise that these variables are often confused or conflated and that they can indeed act independently (e.g. someone can attend school yet be illiterate). The chapter then reviews research that addresses the role of literacy in supporting metaphonological development. The research reviewed focuses primarily on adult speakers and includes research involving healthy speakers, speakers with aphasia, and bilingual speakers; it draws on behavioural studies and also studies involving brain imaging in understanding aspects of the neurobiology of bilingualism and metaphonological processing. The chapter concludes by stating that while there has been a large amount of research into metaphonological skills and influence on speech production, there is still much to understand about how metaphonological processing may differ across languages with different phonological systems.

Part Two: Language specific profiles and practices

Part Two of the text presents a further eleven chapters with ten chapters discussing MSDs in particular language contexts and one concluding chapter. As the majority of these chapters follow a similar pattern, individual summaries of each chapter will not be necessary to gain a full appreciation of their contribution towards the text as a whole. However, this should not under-state the value of each of these chapters in providing the main substance of the text.

The languages that are the focus of Chapters 9 through to 18 are: (9) Zulu and Tswana, by Anita van der Merwe and Mie Le Roux; (10) Chinese (Cantonese and Mandarin), by Tara L. Whitehill and Joan K-Y Ma; (11) Dutch, by Roel Jonkers, Hayo Terband and Ben Maassen; (12) French, by Danielle Duez; (13) German, by Bettina Brendel and Ingrid Aichert; (14) Hindi and Kannada, by R. Manjula and Naresh Sharma; (15) Japanese, by Masaki Nishio; (16) Brazilian Portuguese, by Karin Zazo Ortiz, Maysa Luchesi Cera and Simone dos Santos Barreto; (17) Spanish, by Natalia Melle, María-Teresa Martin-Aragoneses and Carlos Gallego; and (18) Swedish, by Ellika Schalling.

The content of each of these chapters is consistent in presenting firstly a description of the phonological system of the focal language(s) with particular emphasis on identifying the aspects that are different from English. The chapters then describe current availability of assessment and treatment tools for use with speakers with MSDs. Then there is a review of available research that has sought to provide descriptions of MSDs (both dysarthria and apraxia of speech) in the focal language(s) prior to reviewing research focusing on the treatment of MSDs in the language. The majority of chapters then conclude by comparing and contrasting the findings of such research with the respective findings in research on English speakers with MSDs and/or presenting hypotheses about particular features of the focal language(s) which may make MSDs in the language(s) different from those observed in English speakers but which have yet to be empirically investigated.

The final chapter “Conclusion”, by volume editors Anja Lowit and Nick Miller, in summarising the issues raised in the text seeks to address the questions ‘Where are we now?’ and ‘Where do we go next?’. In doing so, Lowit and Miller reiterate the key approaches that the text has attempted to integrate in terms of speech-language pathology and cross-language investigation and state that all chapters presented have important contributions in this respect. The chapter reflects on both the positives and the areas for further improvement that the preceding chapters have highlighted. Some primary suggestions being to simply expand the number of languages under active investigation in relation to MSDs and also the need to increase cross-language comparisons in speakers with MSDs. The chapter also naturally provides several possibilities where the field has great potential for further research and development in terms of description, underpinning theory, and clinical applications.

EVALUATION

Overall, the text succeeds in providing a unique perspective on motor speech disorders (MSDs) that does not conform to the now standard English-centric view of MSDs as presented in a plethora of ‘classic’ texts. Often the approach to linguistic and cultural diversity in these classic texts will simply be to allude to the fact that the linguistic and cultural background of speakers should be considered without actually detailing why and how this should be done. While the topics and issues discussed in this text are obviously ripe for further research, the issues discussed also have immediate relevance to clinical practice. For a text that explores a generally under-researched area, this is an uncommon achievement in presenting concrete suggestions for active clinicians to improve their practices when it comes to working with speakers with MSDs in languages other than English.

Similarly, it is easy to agree with the editors that the accumulated chapters offer much to be disheartened with and much to be excited about with regards to the current state of MSD practice across different languages. It is indeed discouraging to be informed that there are no specific assessment tools for some of the globe’s larger languages (e.g. Hindi). Similarly, the editors, in their concluding chapter, allude to there being no resources available for Arabic. Considering that there is no dedicated chapter focusing on Arabic, it could be assumed that there is so little work related to MSDs and Arabic that a chapter could not come to fruition. Equally, it is encouraging that this text now provides a platform for these issues to be addressed, hopefully in the near future. It is also encouraging to read that where research has been conducted on treatment for MSDs, it appears that there is potential for treatment approaches, originally developed with English-speakers in mind, to have similarly beneficial effects for speakers from other language backgrounds

Part One of the text naturally presents the foundations and context for what follows in Part Two - which is understandable. However, although the flow of chapters in Part Two is easily appreciated, this is not always the case for those in Part One. Some chapters, particularly Chapter 8 on the relationship between phonological awareness and literacy, would benefit from being linked more explicitly to the central themes of the text. While the broad relevance to the issue of speech production is not in question, the link to MSDs was not made explicit beyond stating that assessments used to differentiate between MSDs sometime include tasks requiring metaphonological processing. Along similar lines, one could argue that Chapter 6 on sign languages would have been more effectively located within Part Two of the text, given that the structure and content of the chapter is similar to those in Part Two and that signed languages are legitimate languages just as English, French, and so on, are.

Despite the above minor reservations, it is clear that the chapter authors have been provided with a very specific remit by the text editors, and all have succeeded in producing chapters that present clear and concise reviews of the respective topics. With regard to chapters contained within Part Two, it is clear that there is a great deal of difference between languages with respect to how much research has taken place into MSDs. This is reflected in the relative depth that chapter authors go into in differing sections. For example, some chapters describe the sound system in great depth because of significant differences with the sound system of English (e.g. Chapters on Zulu and Tswana and French), whereas others present relatively brief reviews (e.g. Chapters on Dutch and German). Some chapters are able to report detailed descriptions of specific assessment tools that have been developed for the focal language (e.g. chapters on Chinese, Dutch, Portuguese) whereas others cannot do so because of the lack of such language-specific tools. Similarly the sections reviewing treatment for MSDs vary in length and depth as a consequence of the amount of research conducted in the focal language. This is expected based on the premise of the text, but regardless each chapter feels balanced and complete.

One of the key points that is consistently presented throughout the text both explicitly and implicitly is the importance of Diagnostic Intelligibility Testing (DIT) for the purpose of both describing the manifestation of the MSD and also in identifying possible targets for treatment. Traditional ‘classic’ textbooks on motor speech disorders (e.g. Duffy, 2013) emphasise how intelligibility assessment is one component of a broader protocol providing information on a client’s ability to convey their message to a listener. The current text emphasises the point that much intelligibility assessment that occurs in research settings, and in particular in clinical settings, is not diagnostic in that it does not inform which particular sound contrasts are problematic, i.e. current practice tends to identify that intelligibility is reduced but does not identify what leads to the reduction. Through the explicit discussion of DIT in Chapter three and the descriptions of sound systems of the focal languages in the chapters presented in Part two, the reader is able to gain a fuller appreciation of the importance of the diagnostic component of intelligibility testing. The descriptions of the sound systems of the focal languages then provide a platform for the future development of DITs in these languages which could reasonably be attempted by anyone with a linguistic appreciation for the language in question and a passion for MSDs.

While all chapter authors are well-respected researchers and authors who are in good positions to comment on the current state of research into MSDs in the focal languages, it is unclear as to the extent to which the reviews presented are truly comprehensive and representative. Only one chapter explicitly offers information about an information search protocol in terms of databases sourced to inform the chapter content, although this still only accounts for a small portion of the chapter (Chapter 16 on Brazilian Portuguese). Therefore readers with an interest in MSDs in particular languages are still advised to conduct their own further information searches for assessment and treatment tools and associated research – which is naturally advised anyway but is especially important considering that some chapters allude to ongoing and/or upcoming developments.

A further point that would potentially improve the overall cohesiveness of chapters in Part two is greater consistency in identifying whether the assessment procedures and treatment methods discussed are solely the tools of clinical research or whether they also represent procedures used by clinicians. Some chapters, such as the chapter on Chinese, are quite explicit in denoting that some tools have traditionally been the reserve of research while clinicians have tended to use differing procedures. Other chapters offer detailed descriptions of language-specific tools but do not specify the prevalence of use of these tools in different domains. This is a significant point considering that one of the suggestions for future developments in the concluding chapter is for improved education away from ‘simple and misguided direct translation’ of assessment and therapy materials into other languages.

Overall, this text will surely become regarded as a seminal text in the area of MSDs. Despite the clear emphasis on providing cross-language insights, the researcher or clinician whose work is very much grounded in English-speakers would stand to benefit hugely from reviewing the opening chapters to gain new insight and direction into linguistic approaches to the description, diagnosis and treatment of MSDs – a field which is still dominated by approaches centred on identifying perceptually deviant features of a person’s speech (e.g. breathiness, harshness, etc.). While this legacy from pioneering research by Darley, Aronson and Brown (1975) is acknowledged and respected throughout many of the text’s chapters, it is also abundantly clear, that the field needs to move beyond the strict adherence to these approaches in order to progress – hopefully the current text can facilitate this transition.

REFERENCES

Darley, Frederic., Aronson, Arnold., and Brown, Joe. 1975. Motor Speech Disorders. Philadelphia, PA: Saunders.

Duffy, Joseph. 2013. Motor Speech Disorders: Substrates, Differential Diagnosis, and Management (3rd edn). St Louis, MO: Mosby Elsevier.


ABOUT THE REVIEWER

Christopher Plant holds a Ph.D. in Speech and Language Sciences from Newcastle University, UK (2012) and Masters Degrees in Psycholinguistics & Neurolinguistics (University of Essex, UK) and Language Pathology (Newcastle University, UK). His Ph.D. research focused on investigating the semantic representations of nouns and verbs and their implications for conducting speech and language intervention for people with aphasia. He is currently a lecturer in speech pathology at Griffith University and also Central Queensland University, Australia. He was previously a lecturer in speech pathology at James Cook University, Australia. He can also be found on Twitter ChrisSPlant


Page Updated: 23-Jun-2015