Dyscalculia and dyslexia

Conclusion It is our hope that more practitioners in the field of learning disabilities will include the diagnosis and treatment of dyscalculia as they work with children and older individuals. Although there is much more to be explored, we believe that our clinical experience indicates that information-processing deficits may be a contributory factor in the disability and thus warrant further investigation. Furthermore, we believe that insights gained in the treatment of specific language disability may be fruitfully applied in the treatment of dyscalculia. This paper is a condensed version of a presentation at the 29th Annual Conference of The Orton Society, November 1978, at Minneapolis, Minnesota.     

Naming speed in dyslexia and dyscalculia

In four carefully selected samples of 8- to 10-year old children with dyslexia (but age adequate arithmetic skills), dyscalculia (but age adequate reading skills), dyslexia/dyscalculia and controls a domain-general deficit in rapid automatized naming (RAN) was found for both dyslexia groups. Dyscalculic children exhibited a domain-specific deficit in rapid naming of quantities. This finding is in line with recent assumptions that dyscalculia is associated with a neurobiological deficit in the processing of numerosities. In the dyslexia/dyscalculia group, RAN deficits were additive, that is, the dyslexia/dyscalculia group exhibited the sum of the deficits found in the dyslexia only and dyscalculia only groups. This finding suggests that the cognitive bases of dyslexia and dyscalculia are independent from each other. Within the naming speed paradigm no differential impact of special demands on the executive functions inhibition and shifting was found for any of the four groups.     

Self-concept and self-esteem in developmental dyslexia

Self-concept and self-esteem in two groups of dyslexic children (mainstream placement and SpLD unit placement, total N=63) were examined. Interviews and a questionnaire (the SDQ-1) were utilised, giving a mix of qualitative and quantitative data. Where appropriate, a control group of 57 children without learning difficulties was assimilated into the research design. The main findings were that the presence of dyslexia produced marked effects on the self-concept and self-esteem of children, although this was more apparent in the participants attending mainstream schools than those in SpLD units. The qualitative data revealed that children with dyslexia felt isolated and excluded in their schools, and that, typically, up to half were regularly teased or bullied. The findings were related to self-concept and self-esteem theory, and current educational practice. The limitations in terms of research design and analysis were also noted.     

Derivational morphology and spelling in dyslexia

This exploratory study aimed to evaluate the spelling of derived words by dyslexic adolescents and to verify whether this is associated with lack of vocabulary and/or morphological knowledge. A cross-sectional reading level-design was employed in order to determine differences in spelling, derivational morphology and vocabulary tasks between dyslexic students aged 13+ and age-matched and reading level matched control groups. The study confirmed a profound spelling impairment of dyslexic students in comparison with two control groups but this was not associated with poor vocabulary in relation with their age-peers. In contrast, they exhibited lower levels of morphological knowledge than age-matched controls but equivalent with the reading level controls. These results are interpreted in the light of current developmental models of spelling that support a reciprocal interaction between spelling and metamorphology.     

Gender ratio in dyslexia

This paper is based on a study carried out in Great Britain on a national sample of 11,804 ten-year olds. The first section describes an attempt to pick out cases of “specific developmental dyslexia” (Critchley 1970), a constellation or syndrome of difficulties which some believe to be recognizable clinically. When specified criteria for dyslexia were used, 269 children qualified as dyslexic (2.28 percent of the sample). These included 223 boys and 46 girls, for a ratio of 4.51 to 1. Two possible difficulties in interpreting these data are discussed, and a defense is offered of the criteria used. Since some recent research papers report a gender ratio much nearer 1:1 (Shaywitz et al. 1990; Wadsworth et al. 1992; Lubs et al. 1993), those papers were examined for possible differences in procedure; it was found that the definition of dyslexia they used was “poor reading in relation to intelligence.” We carried out a further analysis on our own data using the same criterion. Of the 494 children who qualified as dyslexic on the basis of discrepancy criteria alone (4.19 percent of the sample), 314 were boys and 180 were girls for a ratio of 1.69 to 1. It seems, therefore, that the apparent differences in gender ratio reported in the literature have arisen because different criteria for dyslexia have been used. We argue that the definition based on clinical criteria leads to a more powerful taxonomy and that the widespread equation of “dyslexia” with “poor reading” is a hindrance to progress.     

Immune disorders and dyslexia

The Geschwind-Behan-Galaburda hypothesis of cerebral lateralization postulates an association between immune disorders and learning disabilities. So far, the empirical evidence for such a relationship has been ambiguous. The present study is an attempt to investigate the hypothesis in a population where all the individuals were affected by immune disorders. Thus, 29 students in a special school for asthmatic children (total number of students in the school: 32) were investigated. A number of reading tests with special focus on word decoding were administered. The parents filled in a detailed questionnaire on the prevalence of reading difficulties and immune disorders among the other family members. The proportion of students with reading problems — especially phonological problems — was much higher than would be expected in a normal population. Among the family members we also found an elevated incidence of both reading problems and immune disorders. A cautious interpreptation of these findings leads to tentative and partial support of the Geschwind-Behan-Galaburda hypothesis.     

Temporal processing in dyslexia

The temporal processing capabilities of 15 children with dyslexia versus 15 age-matched and 15 reading-matched controls in a word identification task were examined. The hypothesis underlying the present experiment was that word recognition would be inferior in children with dyslexia, relative to controls, when the task demanded the temporal integration (sequencing) of two-syllable words. Such a hypothesis must predict that one-syllable word recognition does not distinguish between these two populations and that these effects cannot be accounted for in terms of eye movement differences. To test this hypothesis, one- and two-syllable words displayed for 100, 300, and 3,000 msec were required to be identified. The results yielded evidence of decreased accuracy of word identification by the children with dyslexia in the two-syllable, 300-msec condition, as predicted. A second experiment was unable to uncover any differences in eye movement behaviors that could account for the effects observed in the first experiment. The results are discussed in terms of potential sequential processing deficits in individuals with dyslexia.     

Verbal memory and phonological processing in dyslexia

This study examines whether two frequently reported causes of dyslexia, phonological processing problems and verbal memory impairments, represent a double‐deficit or whether they are two expressions of the same deficit. Two‐hundred‐and‐sixty‐seven Dutch children aged 10–14 with dyslexia completed a list‐learning task and several phonological tasks, together with a number of reading and spelling tests. The results indicate that phonological deficits and verbal memory impairments in dyslexia stem from the same root, which seemingly reflects an inaccurate encoding of the phonological characteristics of verbal information. This phonological encoding deficit is a negative predictor for both the reading and spelling skills of dyslexic children.     

Timing precision and rhythm in developmental dyslexia

Current research on the etiology ofdevelopmental dyslexia is generally informed byeither of two major hypotheses. One of theseassumes that the phonological processing ofconsonants and vowels at a segmental levelidentifies the core deficit in developmentaldyslexia and that it cannot be reduced todomain-general deficits of temporal informationprocessing. The other hypothesis holds thatphonological processing deficits aresymptomatic of an underlying, domain-generaldysfunction; and that at least some dyslexiasubtypes are causally related to domain generaldeficits of temporal information processing forauditory and visual stimuli. This report startsfrom the assumption that the terms temporal information processing andphonological processing as applied in currentdyslexia research, are frequently conflated. Further, it assumes that the conflated termsmust be decomposed into their concretebehavioral referents before the causalsignificance of either can be investigatedsystematically.The studies to be summarized in thisreport represents one step toward suchdecomposition. The findings indicated thatduring a motor sequencing task, dyslexicstudents anticipated the signal of anisochronic pacing metronome by intervals thatwere two or three times as long as those ofage matched normal readers or normal adults.These group differences were significant whenparticipants tapped with the preferred indexfinger alone or with both fingers in unison.Dyslexic students also took significantlylonger than normal readers did to recalibratetheir tapping responses when the metronome ratewas experimentally changed in the middle of atrial.In addition, dyslexic students, bycontrast to normal readers, had inordinatedifficulty reproducing simple motor rhythms byfinger tapping, and similar difficultyreproducing the appropriate speech rhythm oflinguistically neutral nonsense syllables.These difficulties were exaggerated whenparticipants had to synchronize theirperformance to an external pacing metronome.The implications of the findings for temporalinformation processing deficits on one hand,and impaired phonological processing on theother, are discussed.     

Morphological awareness in developmental dyslexia

This study examines morphological awareness in developmental dyslexia. While the poor phonological awareness of dyslexic children has been related to their difficulty in handling the alphabetical principle, less is known about their morphological awareness, which also plays an important part in reading development. The aim of this study was to analyze in more detail the implications of the phonological impairments of dyslexics in dealing with larger units of language such as morphemes. First, the performance of dyslexic children in a series of morphological tasks was compared with the performance of children matched on reading-level and chronological age. In all the tasks, the dyslexic group performed below the chronological age control group, suggesting that morphological awareness cannot be developed entirely independently of reading experience and/or phonological skills. Comparisons with the reading-age control group indicated that, while the dyslexic children were poorer in the morphemic segmentation tasks, they performed normally for their reading level in the sentence completion tasks. Furthermore, they produced more derived words in the production task. This suggests that phonological impairments prevent the explicit segmentation of affixes while allowing the development of productive morphological knowledge. A second study compared dyslexic subgroups defined by their degree of phonological impairment. Our results suggest that dyslexics develop a certain type of morphological knowledge, which they use as a compensatory reading strategy.     

Clock drawing in developmental dyslexia

Although developmental dyslexia is often defined as a language-based reading impairment not attributable to low intelligence or educational or socioeconomic limitations, the behavioral manifestations of dyslexia are not restricted to the realm of language. Functional brain imaging studies have shed light on physiological differences associated with poor reading both inside and outside the classical language areas of the brain. Concurrently, clinically useful tests that elicit these nonlinguistic deficits are few. Specifically, the integrity of the dorsal visual pathway, which predominantly projects to the parietal cortex, remains underinvestigated, lacking easily administered tests. Here we present the Clock Drawing Test (CDT), used to test the visuoconstructive ability of children with and without dyslexia and garden-variety poor readers. Compared to typically reading children, many children with dyslexia and some garden-variety poor readers showed significant left neglect, as measured by the distribution of figures drawn on the left clock face. In the poor readers with dyslexia, we observed spatial construction deficits like those of patients with acquired right-hemisphere lesions. The results suggest that in some children with dyslexia, right-hemisphere dysfunction may compound the phonological processing deficits attributed to the left hemisphere. The CDT provides an easy opportunity to assess skills known to be associated with right-hemisphere parietal function. This test can be easily administered to children for both clinical and research purposes.     

Developmental dyslexia revisited and projected

There are three parts to this paper. First, I review briefly the signposts from research, theory, and application in developmental dyslexia in the 1960s and the 1970s that have led us from there to here, and show the pitfalls to avoid. Second, I discuss some of the pertinent issues of the 1980s: the role of intelligence in the diagnosis of children with specific reading disabilities, the distribution of reading difficulties and disabilities, and the important place of verbal efficiency. Third, I project to the 1990s to emphasize the challenge of the computer technology as mediated learning and the challenge of “bounded rationality” and “collective rationality” in education. Throughout this survey, the paramount role of knowledgeable and caring teachers is implicit. Portions of this paper were given at the British Dyslexia Association Conference on Dyslexia in Bath in 1989 and The Orton Dyslexia Society Annual Conference in Washington, D.C. in 1990. The writing of the paper was assisted in part by research grant No. 410-89-0128 from the Social Sciences and Humanities Research Council of Canada     

The nootropic concept and dyslexia

A review is presented of controlled studies using intensive teaching intervention to improve dyslexics’ reading ability. The results of eight controlled studies reveal only one showing the superiority of teaching. Taking this as a background, the work on Nootropics is reviewed. Both animal and clinical work with Piracetam (the first of the Nootropics) seems to indicate that this medication lacks significant or serious side effects and appears to promote memory and learning. Many double-blind studies of Piracetam have now been conducted on dyslexic children. These studies suggest that Piracetam improves the reading ability of dyslexics. In addition electrophysiological studies support the notion that Piracetam may be “left hemisphere active.” Such encouraging trends will doubtless lead to further research in this interesting area.     

Object-naming deficits in developmental dyslexia

This paper reports two experiments which focus on the object naming deficits of dyslexic readers. In Experiment 1, dyslexic and normal readers were asked to name objects depicted by pictures or following their spoken definition. Ten-year-old dyslexics named fewer objects correctly than other children of a similar age, performing only as well as a younger group of 8-year-old normal readers. This was true irrespective of the modality through which they were tested. In terms of naming latency, however, they were similar to comparison groups. In Experiment 2, nine-year-old dyslexic and normal readers performed as well as each other in a receptive vocabulary test in which pictures had to be matched to spoken words. However, once again, on a picture naming test, the dyslexics did less well than controls. We argue that dyslexic children are subject to verbal naming difficulties which cannot be accounted for by generally low levels of vocabulary knowledge. Their problems are attributable not to difficulties in semantic representation but to difficulties with the lexical-phonological representation of spoken words they know. We propose that, in turn, these difficulties are related to their memory and reading problems.