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.     

Subgroups in dyslexia: Issues of definition

Conclusion The issue of definition in an important one. The answers to the questions raised are not clear, yet they are of both theoretical and of practical importance. With increasing clarification of the underlying deficits of the dyslexias, and with the ability to analyze them within the individual, the opportunity now exists to re-analyze our teaching strategies in order to discover with greater clarity those that are most effective for each definable type of child. This paper was presented as part of a symposium on the definition of dyslexia at the 29th Annual Conference of the Orton Society, Minneapolis, November 1978.     

The misconception of the regression-based discrepancy operationalization in the definition and research of learning disabilities

In this article, I argue that the regression-based discrepancy method used in the diagnosis of learning disabilities is invalid because it is inconsistent with the underlying underachievement concept of which it is intended to be the operationalization. I mathematically demonstrate that the regression-based discrepancy method largely reflects achievement-specific determinants, thereby defeating its own object of describing aptitude-achievement discrepancies. The implications for research examining the role of intelligence in learning disabilities are outlined.     

Retrieval and evaluation of symbolic information in dyslexia

Summary A group of 35 reading disabled boy and 35 matched controls were studied over a two-year period in order to evaluate the validity of traditional hypotheses about the causes of serious reading impairment in preadolescent boys for whom the common disadvantages of economic privation, bilingualism and emotional instability were absent. The popular hypothesis of perceptual deficit was not supported by the data, although the finding that most reading disabled boys have a short-term memory deficit was affirmed. The most important new findings was that about one-fourth of the reading disabled boys had serious difficulty in maintaining an efficient set to process and/or evaluate information, especially when that information was contained in oral speech. This research was supported by a grant from the Lilly Endowment, Inc. We thank Michelle Shal and Susan Grant for their participation in this work.     

RTP-based broadcast streaming of high definition H.264/AVC video: An error robustness evaluation

In this work, we present an evaluation of the performance and error robustness of RTP-based broadcast streaming of high-quality high-definition (HD) H.264/AVC video. Using a fully controlled IP test bed (Hillestad et al., 2005), we broadcast high-definition video over RTP/UDP, and use an IP network emulator to introduce a varying amount of randomly distributed packet loss. A high-performance network interface monitoring card is used to capture the video packets into a trace file. Purpose-built software parses the trace file, analyzes the RTP stream and assembles the correctly received NAL units into an H.264/AVC Annex B byte stream file, which is subsequently decoded by JVT JM 10.1 reference software. The proposed measurement setup is a novel, practical and intuitive approach to perform error resilience testing of real-world H.264/AVC broadcast applications. Through a series of experiments, we evaluate some of the error resilience features of the H.264/AVC standard, and see how they perform at packet loss rates from 0.01% to 5%. The results confirmed that an appropriate slice partitioning scheme is essential to have a graceful degradation in received quality in the case of packet loss. While flexible macroblock ordering reduces the compression efficiency about 1 dB for our test material, reconstructed video quality is improved for loss rates above 0.25%.     

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.     

Differentiating between difficult-to-remediate and readily remediated poor readers: more evidence against the IQ-achievement discrepancy definition of reading disability

In this article we discuss research bearing on the traditional use of the IQ-achievement discrepancy to define specific reading disability. We initially review the evidence presented by Rutter and Yule (1975) in support of this practice, and then discuss results from subsequent studies that have questioned the reliability of their findings. We also discuss results from more recent studies demonstrating that the IQ-achievement discrepancy does not reliably distinguish poor from normal readers, whereas language-based measures do reliably distinguish these groups. We highlight results from a study we recently completed, in which it was found that IQ scores did not differentiate between poor readers who were found to be readily remediated and poor readers who were difficult to remediate. In view of the convergent evidence against the use of IQ scores to define specific reading disability, we suggest that the IQ-achievement discrepancy definition of this disorder be discarded.     

An interaction-dominant perspective on reading fluency and dyslexia

The background noise of response times is often overlooked in scientific inquiries of cognitive performances. However, it is becoming widely acknowledged in psychology, medicine, physiology, physics, and beyond that temporal patterns of variability constitute a rich source of information. Here, we introduce two complexity measures (1/f scaling and recurrence quantification analysis) that employ background noise as metrics of reading fluency. These measures gauge the extent of interdependence across, rather than within, cognitive components. In this study, we investigated dyslexic and non-dyslexic word-naming performance in beginning readers and observed that these complexity metrics differentiate reliably between dyslexic and average response times and correlate strongly with the severity of the reading impairment. The direction of change in the introduced metrics suggests that developmental dyslexia resides from dynamical instabilities in the coordination among the many components necessary to read, which could explain why dyslexic readers score below average on so many distinct tasks and modalities.     

Spelling deficits in dyslexia: evaluation of an orthographic spelling training

Orthographic spelling is a major difficulty in German-speaking children with dyslexia. The aim of the present study was to evaluate the effectiveness of an orthographic spelling training in spelling-disabled students (grade 5 and 6). In study 1, ten children (treatment group) received 15 individually administered weekly intervention sessions (60 min each). A control group (n = 4) did not receive any intervention. In study 2, orthographic spelling training was provided to a larger sample consisting of a treatment group (n = 13) and a delayed treatment control group (n = 14). The main criterion of spelling improvement was analyzed using an integrated dataset from both studies. Repeated-measures analysis of variance revealed that gains in spelling were significantly greater in the treatment group than in the control group. Statistical analyses also showed significant improvements in reading (study 1) and in a measure of participants’ knowledge of orthographic spelling rules (study 2). The findings indicate that an orthographic spelling training enhances reading and spelling ability as well as orthographic knowledge in spelling-disabled children learning to spell a transparent language like German.     

Neuropsychological classification and treatment of dyslexia.

Evidence shows that initial and advanced learning to read are predominantly mediated by the right and left cerebral hemispheres, respectively. Premature reliance on left-hemispheric reading strategies may result in L-type dyslexia, characterized by hurried and inaccurate reading. P-type dyslexia, characterized by a slow and fragmented style of reading, may result from the inability to shift from the predominant generation of right-hemispheric reading strategies to the predominant generation of left-hemispheric reading strategies. Results of investigations concerning the validity of the L/P-typology are discussed, as are the reading effects of hemisphere-specific and hemisphere-alluding stimulation in children with L- and P-type dyslexia.     

An exploratory factor analysis of the cognitive functioning of first-year bachelor students with dyslexia

An increasing number of students with dyslexia register in higher education. As a consequence, information on their pattern of strengths and weaknesses is essential to construct adequate assessment and diagnostic protocols. In a sample of 100 first-year bachelor students with dyslexia and 100 control students, a large pool of cognitive skills were tested using a variety of tests. When we applied an exploratory factor analysis to scores, a model with ten factors fitted the data best. Effect sizes were used to express the processing costs of students with dyslexia. The factors related to reading, spelling, flashed orthography, phonology, naming, math, and reading fluency resulted in large effect sizes. A factor combining all measures for crystallized IQ had a medium effect size. The subtests for fluid intelligence were divided in two separate constructs. Relationships between all subtest scores are visualized and interpreted in a general theoretical and practical framework.     

Evaluating the impact of dyslexia laws on the identification of specific learning disability and dyslexia

Dyslexia is a specific learning disability that impacts word reading accuracy and/or reading fluency. Over half of the states in the USA have passed legislation intended to promote better identification of individuals with dyslexia. To date, no study has been conducted to investigate the potential impact of state laws on the identification of specific learning disability (SLD), and limited data has been presented on the rate at which students in public school settings are identified with dyslexia. The first aim of the current study was to determine if any detectable changes in the identification rates of SLD have occurred in states implementing dyslexia laws because most states do not report number of students identified as dyslexic but rather those students identified with an SLD. The second aim of the study was to characterize the rate of identifying dyslexia in the two states (Texas and Arkansas) that require public schools to report the number of students identified with dyslexia. The third aim was to characterize the identification rate across first to 12th grades. Current SLD rates range from 3.2 to 8.5% in all 50 states. Analysis of SLD prevalence rates did not vary between states with and without dyslexia laws in place. Moreover, there was no change in the identification of SLD once states had implemented these laws. Rates of dyslexia in Arkansas and Texas were less than 5%. Given the persistent levels indicating lack of reading proficiency, our review of data suggests that overall students with dyslexia are being underidentified.     

Neurological aspects of dyslexia: comment on the balance model.

The Balance Model rests on a long history of research that suggests that different subtypes of dyslexia exist. Based on the notion that there are two subtypes of dyslexia, Bakker has articulated a developmental neuropsychological model whereby a procedure known as hemisphere-specific stimulation may be beneficial in treatment. This article reviews Bakker's model and provides a critical examination as to why validating research has not been conducted. While Bakker's Balance Model may hold promise for scientific inquiry, validation of treatment effects are needed prior to employing these procedures in clinical practice. Further, important conceptual issues remain to be addressed.     

An evaluation of evaluation

Conclusion The present evaluation procedures are useful if looked at as secondary data; if they are seen as broad and essentially complementary to the main business of schooling — student learning, and not as the primary outcome of schooling.When they are seen as direct or primary representations of the quality of programs, they are fraudulent and misleading. Moreover, they are dangerous to the humanistic image of man and our evolving understanding of the learning process.It is the heightening of this danger, currently being fostered by federal grant programs, accountability movements, industrial focus, and the national testing program, that makes it crucial to take a stand, now.We who are engaged in schooling activity are being made over by the pressures of our contemporary milieu. As I see it at present, the evaluation signs of the times can only lead, in the long run, to a process whereby we shall become middlemen technicians in schools that perform a service-training function.Distinguished Professor of Education at the University of North Carolina (Greensboro).