Comparing the phonological and double deficit hypotheses for developmental dyslexia

This study tested the predictions of thephonological and double deficit hypotheses byexperimentally examining speech perception,phoneme awareness, lexical retrieval (serialand discrete), articulatory speed, and verbalSTM in school age child (N = 35) and adolescent(N = 36) dyslexics, and both chronological age(CA) and reading age (RA) controls. Theresults confirmed the findings of previousstudies of a deficit in phoneme awareness indevelopmental dyslexia. At both age levels,dyslexics performed significantly more poorlythan both their CA and RA controls. Althoughdeficits in the other processes investigated,particularly in rapid serial naming, were alsoapparent, they were not as clear-cut as thedeficit in phoneme awareness. In general,definite evidence of a deficit in rapid serialnaming was limited to the more severelyimpaired dyslexics. Furthermore, although rapidserial naming contributed independent variationto various literacy skills, its contributionwas modest relative to the contribution ofphoneme awareness, regardless of whether theliteracy skill relied more or less heavily onphonological or orthographic coding skills. Further analyses suggested that variation inrapid serial skill is particularly importantfor fluent reading of text, whereas phonemeawareness is particularly important for thedevelopment of the ability to read byphonologically recoding letters or groups ofletters in words into their phonological codes.This explains the relatively strongcontribution of phoneme awareness to readingand spelling ability in general. In sum, thephonological hypothesis offers a moreparsimonious account of the present resultsthan the double deficit hypothesis.     

The second deficit: An investigation of the independence of phonological and naming-speed deficits in developmental dyslexia

An increasing body of dyslexia researchdemonstrates, in addition to phonologicaldeficits, a second core deficit in theprocesses underlying naming speed. Thehypothesized independence of phonologicalawareness and naming-speed variables inpredicting variance in three aspects of readingperformance was studied in a group of 144severely-impaired readers in Grades 2 and 3. Stepwise regression analyses were conducted onthese variables, controlling for the effects ofSES, age, and IQ. Results indicated thatphonological measures contribute more of thevariance to those aspects of reading skill thatinvolve decoding or word attack skills;naming-speed measures contribute more to skillsinvolved in word identification. Subtypeclassification findings were equally supportiveof the independence of the two deficits: 19%of the sample had single phonological deficits;15% had single naming-speed deficits; 60% had double-deficits; and 6% could not be classified. The implications of these findingsfor diagnosis and intervention are discussed.     

Reading against all odds: a pilot study of two deaf students with dyslexia

Learning to read and write is a challenge for most deaf children due to their limited experiences with, and access to, spoken language. In the case of deaf students who have difficulty processing visual print, literacy becomes an even greater challenge. The study piloted an intervention procedure that incorporated the principles of automaticity, repetition, functional vocabulary, and a positive teacher-student relationship as recommended in programs for struggling readers and adapted them to the needs of two deaf high school students with dyslexia in an American Sign Language-English bilingual program. The findings reveal gains in reading ability on the formal measures, though not more than would be expected over a 6-month period simply due to development. The real improvements were noted in the students' attitudes toward literacy, improved social interaction, and increased self-confidence.     

Cerebral dominance and subtypes of developmental dyslexia

Conclusions Evidence of different syndromes of developmental dyslexia raises the question of the interaction between dyslexic types and patterns of cerebral dominance. Some of the proposed classifications of dyslexia, and most notably the one proposed by Boder (1971), strongly suggest that dyslexic subtypes, that can be identified clinically by reading-spelling patterns, may possess different or opposite cerebral dominance patterns. Thus, research of cerebral dominance in dyslexia (i.e., Orton’s hypothesis) should involve careful selection and classification of subjects. When this is done it can be shown that electrophysiological measures can identify cerebral-dominance abnormalities in at least one subtype of developmental dyslexia. This paper was presented in part at the 29th Annual Conference of The Orton Society, November 1978, in Minneapolis, Minnesota.     

Subtypes of developmental dyslexia: The influence of definitional variables

The purpose of this study was to investigate the hypothesis that the manner in which a reading disability is defined will influence the conclusions that are made about the characteristics of the disability. To test this hypothesis, learning disabled and normally achieving children, aged 6 to 14, were administered tasks measuring grammatical, shortterm memory, phonological, reading, and visual-spatial skills. The poor readers were divided into groups of poor readers with

Ordinary and extraordinary brain development: Anatomical variation in developmental dyslexia

Eight brains, six male and two female, of reliably diagnosed cases of developmental dyslexia have been analyzed in this laboratory thus far. Common to all the specimens is the absence of ordinary asymmetry in the planum temporale, a language relevant area of the temporal lobe. In addition, the male cases and one female case displayed multiple focal areas of malformation of the cerebral cortex, located variably in the language relevant perisylvian regions and to a greater or lesser extent bilaterally. Both female cases and, to a mild degree, one of the males display focal areas of cortical scarring dated to the end of pregnancy through to the end of the second year of life at the latest. The scarring tends to be located in the vascular watershed territories. Experimental animal research suggests that symmetry may represent absence of the necessary developmental pruning of neural networks required for specific functions such as language. This diminished pruning results in excessive neurons and (at least interhemispheric) connections. Additional modeling in experimental animals suggests that cortical malformations and scarring similar to those seen in the dyslexic brains may represent early focal injury that could be attributed to congenital disorders of the immune system. The work reported here has been supported, in part, by NIH grant NICHD 20806, The Orton Dyslexia Society, and the Carl J. Herzog Foundation.     

Teacher and pupil ratings of self-esteem in developmental dyslexia

Neil Humphrey is a lecturer in psychology at Bolton Institute. In this article, based on the research he carried out for his PhD thesis, he explores the relationships between dyslexia and self-esteem in pupils. Neil Humphrey gathered data using both teacher rating scales and pupil self-reporting. He compares results from a group of pupils with dyslexia in mainstream settings; a group attending units for pupils with specific learning difficulties (SpLD); and a control group. In discussing his findings, Neil Humphrey presents practitioners working towards inclusion with a carefully considered challenge.     

Cross-national comparisons of developmental dyslexia in Italy and the United States

This study was designed to examine whether the phonetic regularity of a language can significantly influence the prevalence and pattern of developmental dyslexia. Demographically matched samples of fifth-grade children in Italy (N = 448) and the United States (N = 1,278) were evaluated to identify children with specific reading disabilities. Reading disabled children with average intelligence were compared to normal controls on a series of neuropsychological tests to evaluate specific cognitive deficits associated with reading disorders in each country. The findings suggested that (a) dyslexia is more prevalent in the United States than in Italy, (b) reading disabilities are strongly associated with disorders of verbal processing in both countries, although some American dyslexics also show visual-motor deficits, and (c) there is a greater dissociation between reading comprehension and decoding in Italian than in English.     

Motor skills, automaticity and developmental dyslexia: A review of the research literature

This paper reviews a body of prominent theoriesof automaticity in developmental dyslexia. Thefirst part of the review considers therelationship between dyslexia and rapidautomatic naming and fluency. Additionaltheoretical and empirical advances aresuggested to this already strong research base.In particular, there is a need is forexperimental work elucidating the nature ofnaming speed deficits and providing independentevidence of the automaticity of rapid naming.The second part of the review considersevidence for deficits in motor automaticity indyslexic children. Here, a more mixed patternof results is evident. It is concluded thatthere is currently clearer evidence forlanguage-based than motor-based automaticitydeficits. Future motor automaticity research islikely to require the routine screening of poorreaders for common co-occurring developmentaldifficulties, improved sampling and prospectivelongitudinal studies.     

The early manifestation of developmental dyslexia: Evidence from German children

The present study retrospectively examined early difficulties with phonological coding and phonemic segmentation of German children who after four years in school were diagnosed as dyslexic. German, in comparison to English, exhibits rather simple and straight-forward grapheme-phoneme correspondences, and the initial teaching approach was phonics oriented. Despite these favorable circumstances for the acquisition of phonological coding, the majority of the later dyslexic children had particular difficulties with the accurate reading of nonwords and of unfamiliar words after about seven months of reading instruction. However, there were enormous differences between the dyslexic children. Two of them were completely unable to blend phonemes into pronunciations, another seven were slow and error prone decoders, and three children had slow and laborious pronunciation assembly as the core problem. The majority of the later dyslexic children also exhibited phonemic segmentation deficits as tested with a nonword spelling task and a phoneme reversal task. In correspondence with findings from older German dyslexic children, the early difficulties with accurate phonological coding and phonemic segmentation were no longer found at the end of grade four. Children then suffered from very slow reading and poor spelling. In general, the difficulties of German dyslexic children emphasize the phonological impairment account of dyslexia. More specifically, these findings suggest that the assembly of letter sounds into pronunciations is particularly affected in the early phase of learning to read a consistent orthography.     

Auditory processing interventions and developmental dyslexia: a comparison of phonemic and rhythmic approaches

The purpose of this study was to compare the efficacy of two auditory processing interventions for developmental dyslexia, one based on rhythm and one based on phonetic training. Thirty-three children with dyslexia participated and were assigned to one of three groups (a) a novel rhythmic processing intervention designed to highlight auditory rhythmic information in non-speech and speech stimuli; (b) a commercially-available phoneme discrimination intervention; and (c) a no-intervention control. The intervention lasted for 6 weeks. Both interventions yielded equivalent and significant gains on measures of phonological awareness (at both rhyme and phoneme levels), with large effect sizes at the phoneme level. Both programs had medium effect sizes on literacy outcome measures, although gains were non-significant when compared to the controls. The data suggest that rhythmic training has an important role to play in developing the phonological skills that are critical for efficient literacy acquisition. It is suggested that combining both prosodic/rhythmic and phonemic cues in auditory training programs may offer advantages for children with developmental dyslexia. This may be especially true for those who appear resistant to conventional phonics training methods.     

Reading difficulties and attention‐deficit/hyperactivity behaviours: evidence of an early association in a nonclinical sample

Attention‐deficit/hyperactivity disorder (ADHD) often co‐occurs with reading disability. A cross‐sectional study in an Italian‐speaking, nonclinical sample was conducted in an attempt to document the existence of an early association between reading difficulties (RD) and ADHD behaviours. We recruited a sample of 369 children in their first year at primary school. Of the sample, 8.4% displayed RD; 7.0% had ADHD; 3.5% presented both RD and ADHD behaviours; 50% of the children with ADHD displayed RD; 41.9% of those with RD displayed ADHD behaviours. Low socioeconomic status was associated with a fourfold increased probability of displaying RD (odds ratio = 3.98), but not ADHD behaviours. In this nonclinical sample, we detected an early association between ADHD behaviours and RD. A key role in this association may be played by inattention symptoms, which occurred with significantly increased frequency also in the group presenting only RD.     

What time may tell: Towards a new conceptualization of developmental dyslexia

This paper is a written version of the Norman Geschwind Lecture delivered to the International Dyslexia Association on November 13, 1998. The first purpose is a theoretical one: to describe a new conceptualization of reading disabilities, the double-deficit hypothesis, that depicts and integrates work on two core deficits in the phonological system and in processes underlying naming speed. Implications for subtyping, diagnosis, and, in particular, intervention are described. The second purpose is to thank the women and men whose commitment to children with reading disabilities has transformed our field over the last century. Within that double set of purposes, I wish to dedicate this paper to five research teachers whose insights have been the foundation for my work and the efforts of many of us in the field of reading disabilities research: Jeanne Chall, Carol Chomsky, Martha Bridge Denckla, Helen Popp, and especially, Norman Geschwind.     

汉语发展性阅读障碍的语素意识缺陷研究

在汉语发展性阅读障碍研究领域,研究者越来越关注语素意识。而语素意识缺陷是否为汉语阅读障碍的核心缺陷,这一争论到目前尚未有定论。不过,语素意识在汉语阅读中确实有着非常重要的作用。本文通过查阅各种文献,对汉语发展性阅读障碍的语素意识缺陷研究做了一个梳理。     

Continuities between speech and spelling in a case of developmental dyslexia

This paper explores the relationship between speech and spelling in a single-case study of developmental dyslexia. JM, a developmental dyslexic with a well-documented history of speech, reading and spelling difficulties, was examined when he was 13–14 years old. He still had subtle articulation difficulties causing some disfluency and his use of phonetic voicing was atypical. We argue that these difficulties were recapitulated in his spelling where he was more sensitive to the prosodic aspects of words than normal spellers, exhibiting a strong tendency to spell accurately words which are stressed on the first, rather than the second syllable. He also had more difficulty with phonetic voicing and spelling errors reflected this uncertainty. Thus, when word-specific (orthographic) spelling information is unavailable, JM, like all spellers, must make use of phonological spelling strategies. In his case, these are compromised because of underlying phonological speech problems. It is argued that, while young children make use of a phonological frame on which to organize orthographic information, dyslexics, like JM, who have inadequate phonological representations, are unable to do so. This has a detrimental effect on their acquisition of spelling.     

Reading development and dyslexia in a transparent orthography: a survey of Spanish children

Spanish-speaking children learn to read words printed in a relatively transparent orthography. Variation in orthographic transparency may shape the architecture of the reading system and also the manifestation of reading difficulties. We tested normally developing children and children diagnosed with reading difficulties. Reading accuracy was high across experimental conditions. However, dyslexic children read more slowly than chronological age (CA)-matched controls, although, importantly, their reading times did not differ from those for ability-matched controls. Reading times were significantly affected by frequency, orthographic neighbourhood size and word length. We also found a number of significant interaction effects. The effect of length was significantly modulated by reading ability, frequency and neighbourhood. Our findings suggest that the reading development of dyslexic children in Spanish is delayed rather than deviant. From an early age, the salient characteristic of reading development is reading speed, and the latter is influenced by specific knowledge about words.