A definition of dyslexia

This paper elaborates on the components of a working definition of developmental dyslexia. It follows the general format of a paper by Lyon published in Annals of Dyslexia in 1995, which elaborated on a working definition proposed in 1994 (Lyon, 1995). The current definition agreed on by the work group updates and expands on the working definition from 1994.     

Developmental dyslexia: A review of biological interactions

The discovery of biological substrates underlying medical conditions is an important step for their better understanding and for the design of appropriate medical therapies. In the case of developmental dyslexia pedagogic treatment may fail, thus creating a group of individuals in whom medical approaches may be entertained. The biological substrate(s) of developmental dyslexia has yet to be specified, although a few clues are beginning to emerge. In this review I consider the issue of cerebral dominance and brain asymmetry, the development of the cerebral cortex and examples of aberrancy, and diseases of the immune system, all of which relate to recent anatomical and epidemiological findings in developmental dyslexia. These discoveries have been able to lead to the creation of testable hypotheses which, after appropriate experimental work, are apt to enhance our current understanding of this and other developmental learning disorders.     

A developmental framework for developmental dyslexia

There are surprisingly few theories of the normal development of literacy that take into account the different cognitive processes underlying reading and spelling skills. The present framework suggests three phases, corresponding to the acquisition of logographic, alphabetic, and, finally, orthographic skills. At each phase, a new skill is introduced with either reading (input processes) or writing (output processes) acting as pacemaker. This stepwise progress is driven by a certain opposition between reading and writing processes. At any of the critical points where a new step has to be taken, breakdown can occur. This will result in different types of literacy disorder. However, the disorder will not only be characterized by the deficiency in a particular skill, but also by compensatory skills which will inevitably develop. Only by using models of this type will we be able to achieve a properly developmental perspective for developmental dyslexia.     

A developmental investigation of word length effects in reading using a new on-line word identification paradigm

Third and fifth grade children (average age 8.6and 10.6 years) and adult participants weretested with printed words of varying length ina new on-line identification task (theluminance increment paradigm, LIP) and aspeeded naming task. Effects of general length(length in letters, phonemes and syllables)were shown to decrease systematically with agein both tasks. Third grade children showedsubstantial effects of word length while theeffect practically disappeared in adults. Ingeneral, this developmental pattern was alsofound when separately examining effects ofphonological length (with length in lettersheld constant) and small unit length (withnumber of syllables held constant), althoughsome differences were observed in performancein the identification and the naming task. Thetwo tasks also showed different developmentalpatterns, with the greatest gain in performancearising between 3rd and 5th grade inthe naming task, and the largest improvementoccurring between 5th grade and adults inthe identification task. The results suggestthat the new luminance increment paradigm canbe usefully applied as an on-line measure ofprinted word perception in beginning readers.     

An investigation of grapheme parsing and grapheme-phoneme knowledge in two children with dyslexia

The aim of this study was to understand the relationship between children’s knowledge of letter-sound rules (“grapheme-phoneme knowledge”) and their ability to identify separate graphemes (e.g., SH, OI) that comprise words (“grapheme parsing”). We used a single-case study approach with children with phonological dyslexia who were able to read words accurately via whole-word processes (“lexical reading”), but were not able to read using grapheme-phoneme knowledge (“non-lexical reading”). These children were able to correctly parse some graphemes without grapheme-phoneme knowledge for these graphemes. However, they were unable to correctly parse some graphemes for which they had grapheme-phoneme knowledge. This dissociation suggests that children may acquire grapheme-phoneme knowledge and phoneme parsing independently. We discuss the implications of these findings for cognitive models of word reading.     

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.     

Historical perspectives on dyslexia.

This article begins with an historical overview of the neurological aspects of dyslexia, which was originally seen as a member of the family of aphasias. That overview is followed by a brief review of familial and genetic factors in developmental dyslexia. The article then presents psycholinguistic models of dyslexia as they relate to the neurological concepts. Finally, the author reviews briefly the evolution of methods that have been successful in the remediation of dyslexia.     

A clinical model for treatment of dyslexia

Children with moderate learning disabilities often fail to qualify for special education programs in public schools, but are ill-suited for placement in private schools concerned with the severely disabled. Parents of such children may place their hopes in the promises of private teachers or clinics. Yet the quality of services provided in the private sector varies widely. This paper describes a model program against which parents and private service providers can measure the strengths and weaknesses of the programs they are concerned with. The model places special emphasis on thorough evaluation, frequent reevaluation, staff accountability, program flexibility, and recognition of the parents’ role in the child’s education.     

Reversing letters and reading transformed text in dyslexia: A reassessment

The visual deficit hypothesis of development dyslexia has largely been abandoned because many of the phenomena that initially motivated it could not be replicated under controlled experimental conditions, while phonological processing deficits were found to provide a better explanation for the replicable phenomena. Nevertheless, many teachers and special educators continue to subscribe to the hypothesis that deficits of visual perception are a major cause of reading failure in dyslexia. As part of a larger family study, we reexamined the questions (1) whether probands and affected relatives in dyslexia families reverse easily confused letters more frequently under experimental conditions than normal readers from the same families, and (2) whether they show unusual facility in reading geometrically transformed text. The findings indicated that young dyslexia students reverse easily confused letters more often than normal readers. Reading group differences of letter reversal were significant in children from 7–10 years but not thereafter; and virtually no subject reversed letters when spelling whole words. Furthermore, dyslexic persons in every age group from 7–60 years actually took longer than normal readers to decode geometrically transformed text; and the time to decode transformed texts increased progressively with age after adolescence in both dyslexic persons and normal readers. Thus, reading group differences in decoding easily confused letters and reading geometrically transformed text do not support the visual deficit hypothesis and probably do not help to clarify the etiology of developmental dyslexia.     

The Universal and the unique in dyslexia: A cross-linguistic investigation of reading and reading fluency in Hebrew-and English-speaking children with reading disorders

Cross-linguistic studies provide a unique tool for the identification of universal processes in oral and written language, both in development and in breakdown (Annual Review of psychology, 52, 369–396). Examining the differential strengths and weaknesses of children with dyslexia in contrasting orthographies can help illumine both the more universal aspects of reading disabilities, as well as their individual language-specific attributes. The aim of this study, was to investigate the shared and distinctive characteristics of readers with dyslexia on reading and reading fluency across Hebrew and English orthographies. Differences between 60 Hebrew and English-speaking children with dyslexia on a battery of cognitive, linguistic, and reading measures will be discussed along with theoretical implications.     

Long‐term effects of a psycholinguistic treatment for dyslexia

Short and long‐term effects of a treatment for dyslexia are evaluated. The treatment is based on psycholinguistic theory and assumes that dyslexia is due to poor lexico‐phonological processing of words. The treatment is computer‐based and focuses on learning to recognise and to make use of the phonological and morphological structure of Dutch words. The results of the treatment were clear improvements in reading words, reading text and spelling. Effect sizes of standardised treatment gains were large (Cohen's d>0.80 for all variables). Following the treatment, participants attained an average level of text‐reading and spelling. The attained level of reading words and reading text was found to be stable over a four‐year follow‐up period. Spelling showed a slight decline one year after the treatment, but remained stable thereafter. ¹ 1. A preliminary report of the data was presented at the World congress on dyslexia, September 1997, Thessaloniki, Greece.     

因特网在新产品开发中的应用:一个概念模型

网络时代的一个显著特征是技术日新月异,产品的生命周期缩短,因此,不断利用新技术开发新产品,是企业在竞争中不败的法宝。本文基于Montoya-Wiess和Calantone对新产品开发影响因素的研究框架,分公司战略、新产品开发过程、市场环境和组织环境四个维度,分析了因特网在企业新产品开发中的作用。     

Neuropsychological intervention in dyslexia: two studies on British pupils

The theoretical context of this research is developmental neuropsychology--in particular, the educational implications for the classification of and intervention in specific developmental dyslexia (SDD). Controlled and validated research can help identify optimal teaching methods for groups and individuals. Within this framework, neuropsychological theory can be explored as a medium for improving intervention for pupils with SDD. Neuropsychological stimulation cannot change the macro aspects of the brain but can change its "finetuning" and its response to written text. Within the psycho-neurological approaches, Bakker (1979, 1990, 1998) developed both a diagnostic procedure and empirically investigated intervention procedures. The theory rests on the Balance Model of learning to read, in which differential hemisphere involvement is implicated in beginning and advanced reading. Intervention can take place via hemisphere-specific stimulation using visual or tactile stimulation or hemisphere-alluding stimulation using modified text. Two investigations are presented, one experimental and another clinical. The results support the validity of dyslexia subtyping and the effectiveness of the treatment methods.