Assessing Dyslexia

Becky Kennedy, Kathleen Ryan

• Publisher: Routledge
• Year: 2021
• ISBN:
  9781000349399
• Edition: 1
• Topic: Education
• Subtopic: Learning Disabilities

Assessing Dyslexia guides readers through the design, administration, and interpretation of dyslexia assessments. Grounded in research on the linguistic and neural foundations of dyslexia, as well as the clinical outcomes of reading and writing processes, this concise volume provides a comprehensive framework for assessment, diagnosis, and intervention. Utilizing detailed examples to illustrate methodology and concepts, this book is critical reading for students looking to deepen their understanding of assessment, literacy, and the written language challenge.

1 The Study of Dyslexia

Dyslexia

Dyslexia is a specific learning disability that is neurobiological in origin. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.

(International Dyslexia Association, 2002; see Lyon et al. 2)

Dyslexia, challenge in learning to read, is the most commonly occurring developmental learning challenge and is profound in its effect. The dyslexic child struggles to master reading and writing skills; while peers engage with text, the dyslexic student seeks access to a world of print. We cherish the rewards of that access: the ability to travel beyond spatial and temporal limits through literacy. Reading and writing permit each of us to maintain an interior discourse with the self, as well as a dialogue with those who have preceded, those who will follow, and those who will never be encountered: to bypass the contingencies of time, place, memory, and presence. Through the literacy activities of reading and writing, communities, too, advance to a level of complexity and novelty that would be impossible without the platform of text.

As the capacity to be literate changes the individual and transforms society, the reading brain has also undergone a rearrangement. Neurological circuits designed for other functions have been recruited to accommodate the cultural invention of the print code: In order to engage in the artifice of text creation and recognition, we capitalize on our command of the spoken language we have naturally and spontaneously acquired and on its neurological underpinnings. Speaking and listening are the outcomes of an evolved and innate capacity, and we are pretuned to human speech when we acquire spoken language. Written-language forms are, in contrast, invented; writing is a cultural tool, and we are not prepared neurologically to process written text. As we recode our natural language output in written form, reassembling spoken forms as written text, the complete but implicit knowledge of language structures that we use continuously but subconsciously in spoken expression and communication must be made cognitively visible to us: Our implicit knowledge of language must be made explicit. We apprehend spoken language at a precognitive level; a speaker and listener need not be cognizant of the units of spoken language in order to produce and process speech. On the other hand, the reader who encounters written language and the writer who generates print must utilize those very objects that the speaker and the listener are at liberty to disregard: the minimal segments of spoken language. It is here that dyslexia begins.

The study of dyslexia represents one of the most successful research enterprises on which the modern global intellect has embarked. The findings of educators, clinicians, psychologists, and neurologists have directed researchers toward highly productive agendas that have deepened our understanding of dyslexia’s sources and have inspired the development of innovative, effective treatment programs. One characteristic of dyslexia that has fueled efforts to probe its source and refine its treatment is its demographic indifference. Like the great universals of the human condition—faith, death, love, suffering—dyslexia does not select for economic or social class, nor parenting philosophy, nor academic curriculum, nor instructional excellence, nor intelligence quotient, nor spoken-language culture, even though every one of these putative learning factors has a special effect on outcomes for a dyslexic learner. The etiology of dyslexia is neural; situated neurologically, too, are the reading process and the processing of the spoken language on which a writing system is based. Critical in the character of dyslexia, however, is its insularity: The challenged single-word reading and spelling that are the hallmarks of dyslexia need not be accompanied by other types of learning difficulties or by circumstantial challenges. Dyslexia may but need not be accompanied by attention challenge, spoken-language challenge, challenge in text comprehension, curricular disadvantage, or a home dialect that is different from the cultural grapholect—the literacy dialect.

Advances in our understanding of skilled and challenged reading benefit from the productive intercourse of international, intercultural, and interdisciplinary efforts to understand and treat dyslexia. Key insights have been attained regarding the nature of the underlying deficit, its presentation, the pertinent neural underpinnings, and the genetic sources.

Insights from Natural Language

The preceding observations invite a question: If it is the spoken language that the brain, in the presence of minimal spoken-language data in social context, is configured to acquire naturally, whereas the written language is constructed, both in its organization and in its neurological circuits, on components designed on behalf of the spoken form, why would difference in the brain base impede written-language functions without a concomitant disruption of the spoken language? The insight that resolves this question implicates the relation between spoken and written language and illuminates the core challenge in dyslexia.

Written language is founded on spoken language; decades of research indicate that both the achievement of reading and the challenge to reading that appears in dyslexia are understood in terms of aspects of the phonological component of spoken language. The phonological system of language is the sound module; the phonology of a language includes its inventory of distinctive sounds and the sound features that distinguish them, as well as the structural principles that govern their interaction. The minimal sound unit in that phonological system is the phoneme; the phoneme is an abstraction, representing a set of speech sounds that, for native speakers of any language, are perceived as equivalent in sound value. A phoneme may be variously realized on a phonetic (speech sound) level, depending on its phonological context in the speech stream. For instance, in the following sentence, the instances of the phoneme /t/ vary at a phonetic (perceived speech sound) level: Tim Burton stole a pat of butter from the tray. Speakers and listeners collapse the distributional variants of /t/ and observe that the phoneme /t/ occurs six times in the sample sentence; phonetic attention reveals, though, that each instance of /t/ in that sentence has a distinctive phonetic realization, conditioned by its local speech context. Crucially, the speaker and the listener need not achieve explicit awareness of those distinctive phones (sounds) in order to issue and process the sentence. Liberman (Speech) characterizes the phones of speech as gestures rather than sounds. In forming a syllable, the speaker produces a sequence of gestures, each of which is associated with a target phoneme, but those gestures are folded together in syllabic context by an efficiency-driven coarticulation, under which gestures merge and overlap in the service of speed. The listener in turn unpacks that syllable as a sequence of phonemes; the match between speaker intention and listener perception is achieved because both are tuned by a special, automatized speech mode of perception (439).

Speech and writing diverge here: The speaker and the listener need not be aware of the phonemic composition of the syllable or of the word, but the reader and speller must draw on awareness of phonemic segmentation in order to decode and encode print messages. And this difference between speech and writing is critical to an understanding both of the achievement of reading and of the failure of that achievement. Written languages that utilize alphabetic systems are founded on the alphabetic principle: Graphic symbols map onto the sounds of spoken language. English graphemes—letters and letter clusters—represent the English phonemes. As Liberman observes, reading and writing processes have critical roots in spoken language, yet the two modes of communication divaricate in important ways. Spoken language is biological in its provenance; written language is a cultural artifact. In order to produce or apprehend spoken forms, a speaker and a listener need not be aware of their phonetic structure, because those forms are “the automatic results of a precognitive specialization for phonological communication” (Liberman, Speech 444). Acquisition of natural (spoken) language therefore neither requires the segmentation of a syllable as a string of phonemes nor prepares the speaker to master the alphabetic principle. Liberman and Whalen explain that when learning to read, however, “the child must … learn to put his attention where it never had to be … Speech does not require phonemic awareness” (193). Spoken and written language differ with respect to the role of the abstract phoneme in language processes; this difference underlies the profound significance of the phoneme’s abstract character to the achievement of reading skill and to the failure of that achievement.

Alvin Liberman’s groundbreaking work on speech production and perception had its roots in a 1944 project: Liberman was invited by scholars at the Haskins Laboratories in New Haven, Connecticut, to help develop the sound output for a reading machine for the blind. In this instrument, each printed letter would be translated as a distinctive sound that the blind user would associate with a consonant or vowel sound in the language. Scanning print, the machine would pair each alphabet letter with an acoustic pattern that could be learned and recognized by the user. Under the view of speech assumed in this enterprise, which Liberman calls the conventional horizontal view, speech is composed of an “acoustic alphabet, with segments of sound as discrete as the letters that convey them” (Liberman, “How Theories of Speech” 4). Under that conventional view, speech comprises a constituent sequence of sounds, perceived by general cognitive/auditory capacities; each sound arrives at phonetic significance via a cognitive translation. In this horizontal model, the listener would understand speech in the same way that print is apprehended, interpreting each sound in sequence—just as, in reading, the letters that constitute a text are interpreted in sequence. In both cases, the units—sounds and letters—would be strung together like beads on a string.

Liberman’s project failed, because the temporal resolving power of the human ear was inefficient under these conditions (Liberman, Speech 6): The rate of normal speech is ten times the maximal rate at which reading machine users could follow and interpret a translated acoustic pattern sequence. That failure inspired Liberman’s lifelong research agenda, as he sought to understand what afforded natural speech its special rate and efficiency. Liberman concluded that speech was not a general auditory signal comprising a sequence of sounds of a general auditory type; under Liberman’s unconventional vertical view, the phonemes—basic units—of speech are not concrete auditory entities but instead articulatory gestures that do not line up as would beads in a necklace but, rather, overlap and merge in efficient articulation of the syllable. This view is termed vertical because a vertical view of language is adopted, such that “speech is a constituent of a vertically organized system, specialized from top to bottom for linguistic communication” (Liberman and Whalen 187). From syntax to phonetics, structures and processes are special to language. The speaker’s signal codes gestures linguistically; the listener in turn hears speech and resolves the speech signal by recovering the phonemic code of that speech stream.

The language-specific coding and retrieval processes of, respectively, the speaker and the listener permit parity in the expression and reception of that signal. Crucially, however, these processes are precognitive; they are cognitively opaque: “Because the speech specialization is a module, its processes are automatic and insulated from consciousness” (Liberman, Speech 442). Before they read, children are aware of words, but neither a speaker nor a listener need be aware of phonemes—of the abstract gestural units of the speech stream—in order to formulate or perceive speech. Articulating an insight that is of critical significance both in educational curriculum design and in an understanding of dyslexia, Liberman reminds us that “phonological awareness, which is necessary for application of the alphabetic principle, does not come for free with mastery of the language” (Speech 442). Speaking does not entail awareness of the internal composition of the speech stream; in fact, the qualities of speech that make it most effective for communication obscure further any distinctive reflexes of its abstract units.

Articulation and gestural merger efface recognizable correspondences between the acoustic stimulus—the syllable—and its abstract phonemic constituents. Liberman concludes, “Reading/writing are hard just because speaking/listening are easy” (Speech 429). Prioritized by its natural status, “speech is a product of biological evolution,” while writing “is a triumph of applied biology” but is, itself, “an artifact” (435). This last insight—that speech is an evolved capacity and writing is an invented tool—accounts for the robustness and effortlessness of spoken-language acquisition but also predicts the wide variation observed in individual reading and spelling achievement trajectories.

The critical distinction between the natural character of spoken language and the artificial nature of written language points us toward the overarching challenge of dyslexia: As Liberman asserts and Shaywitz emphasizes, “The effortless and seamless nature of spoken language has everything to do with why reading is so hard for dyslexic children” (Shaywitz 49). Shaywitz points out that speaking and reading reference the same building block, or “particle”: the phoneme, an abstract linguistic sound unit. As Liberman’s account of speech processing indicates, the phoneme serves as a codal interface between speech production and speech perception; reference by both parties to that abstract phonemic level permits parity across expression and reception, and the precognitive nature of that reference permits the efficiency that makes speech communicatively meaningful. That cognitive opacity, however, obviates for the speaker a requirement that is fundamental to the reader: phonemic transparency. Written language references the phonology of spoken language as intermediary between the code of text and its content. The speaker encounters speech with an innate preparedness to process it linguistically; the reader, however, is not equipped with a similar innate and precognitive disposition to process text. The speaker is pretuned to the data of speech; the reader is not pretuned to alphabetic data.

Phonemic Awareness and Dyslexia

Liberman’s account of the difference between speech and reading illuminates the critical contribution of the young reader’s achievement of phonemic awareness in reading development; it also elucidates the special vulnerability of phonemic awareness in dyslexia. Uhry and Clark note the complex relationship between phonemic awareness and reading: Phonemic awareness is “causal” (101) in the mastery of single-word decoding (cf. Bradley and Bryant). The causal relationship between phonemic awareness and decoding achievement, moreover, is bidirectional; decoding growth fosters capacity to analyze the speech stream at the abstract phonemic level. Morais and Mousty argue for this “interactionist position” that “the causes of phonemic awareness are mainly two: linguistic development and alphabetic instruction” (194).

In this regard, Vellutino and Fletcher review the challenges observed in dyslexic readers: They note that operationally, dyslexia in struggling young readers is “manifested in basic and pervasive deficiencies in word identification, phonological (letter-sound) decoding, and spelling” (363): in vitiated response to text, that is, at the single-word level. They remind us that challenged linguistic processing at the sentence and text levels—manifested as reductions in language comprehension, syntactic processing, and vocabulary apprehension—may but need not accompany challenged decoding and encoding of single-word print; crucially, however, single-word decoding competence has been shown (e.g., Hoover and Gough) to be requisite for skilled reading of print: for reading competence. Vellutino and Fletcher point to

convergent evidence that most children with dyslexia have significant difficulty learning to map alphabetic symbols to sound and acquiring facility in phonological decoding … Such difficulties, in turn, appear to be related to limitations in their ability to acquire phonological awareness … [with] evidence for a causal relationship between deficiencies in phonological awareness and alphabetic mapping on the one hand and difficulties in acquiring facility in word identification and spelling on the other.

(Vellutino and Fletcher 364)

This observed causal chain underscores the status of the phonological processing deficit as the core deficit in dyslexia.

Liberman’s insight that reading is hard because speech is easy (Speech 427) is fundamental: The opacity of the abstract phonemic level of spoken language is due to the precognitive character of speech processing. Abstract phonemic segments code speech but are not consulted for the production and processing of the speech stream; for reasons of efficiency, both speech production and speech processing are automatic and precognitive in their occurrence. Incipient readers are not biologically prepared to segment the sound stream of language into abstract phonemes; many children learn phonemic segmentation, but about one in five children will struggle to segment phonemically. However, phonemic awareness, the “insight that every spoken word can be conceived as a sequence of phonemes” (Adams 15), is critical to the activation, for reading and spelling success, of the alphabetic principle that letters and letter sequences map to phonemes. Children who do not perceive the speech stream as a sequence of abstract phonemic segments will struggle to master the alphabetic principle and will not build a bank of phonics sound–symbol associations; unable to break down or build up a word phonemically, they are challenged by alphabetic reading and spelling.

Confirming the status of phonemic awareness as a critical dyslexia deficit, researchers find that a range of tasks that require phonological processing and alphabet–phoneme mapping challenge dyslexic children: phoneme segmentation, word attack (the decoding of ort...