Karin Landerl

The impact of orthographic consistency on dyslexia: A German-English comparison

We examined reading and phonological processing abilities in English and German dyslexic children, each compared with two control groups matched for reading level (8 years) and age (10-12 years). We hypothesised that the same underlying phonological processing deficit would exist in both language groups, but that there would be differences in the severity of written language impairments, due to differences in orthographic consistency. We also hypothesized that systematic differences due to orthographic consistency should be found equally for normal and dyslexic readers. All cross-language comparisons were based on a set of stimuli matched for meaning, pronunciation and spelling. The results supported both hypotheses: On a task challenging phonological processing skills (spoonerisms) both English and German dyslexics were significantly impaired compared to their age and reading age controls. However, there were extremely large differences in reading performance when English and German dyslexic children were compared. The evidence for systematic differences in reading performance due to differences in orthographic consistency was similar for normal and for dyslexic children, with English showing marked adverse effect on acquisition of reading skills.

Development of Word Reading Fluency and Spelling in a Consistent Orthography: An 8-Year Follow-Up

In a longitudinal study, development of word reading fluency and spelling were followed for almost 8 years. In a group of 115 students (65 girls, 50 boys) acquiring the phonologically transparent German orthography, prediction measures (letter knowledge, phonological short-term memory, phonological awareness, rapid automatized naming, and nonverbal IQ) were assessed at the beginning of Grade 1; reading fluency and spelling were tested at the end of Grade 1 as well as in Grades 4 and 8. Reading accuracy was close to ceiling in all reading assessments, such that reading fluency was not heavily influenced by differences in reading accuracy. High stability was observed for word reading fluency development. Of the dysfluent readers in Grade 1, 70% were still poor readers in Grade 8. For spelling, children who at the end of Grade 1 still had problems translating spoken words into phonologically plausible letter sequences developed problems with orthographic spelling later on. The strongest specific predictors were rapid automatized naming for reading fluency and phonological awareness for spelling. Word recognition speed was a relevant and highly stable indicator of reading skills and the only indicator that discriminated reading skill levels in consistent orthographies. Its long-term development was more strongly influenced by early naming speed than by phonological awareness.

The double-deficit hypothesis and difficulties in learning to read a regular orthography

In 2 large longitudinal studies, we selected 3 subgroups of German-speaking children (phonological awareness deficit, naming-speed deficit, double deficit) at the beginning of school and assessed reading and spelling performance about 3 years later. Quite different from findings with English-speaking children, phonological awareness deficits did not affect phonological coding in word recognition but did affect orthographic spelling and foreign-word reading. Naming-speed deficits did affect reading fluency, orthographic spelling, and foreign-word reading. Apparently, in the context of a regular orthography and a synthetic phonics teaching approach, early phases of literacy acquisition (particularly the acquisition of phonological coding) are less affected by early phonological awareness deficits than are later phases that depend on the build up of orthographic memory. The double-deficit hypothesis was developed by Maryanne Wolf and Patricia Bowers as an extension of the dominant phonological-deficit explanation of developmental dyslexia (e.g., Bowers & Wolf, 1993; Wolf & Bowers, 1999). The phonologicaldeficit hypothesis postulates an early difficulty in acquiring phonological awareness, which interferes with the acquisition of grapheme-phoneme coding as a word recognition mechanism, which in turn results in reduced self-teaching of orthographic word representations (Share, 1995). The early problem with phonological awareness is seen as resulting from less sharp phoneme boundaries in speech perception (Fowler, 1991) or from less distinct phonological word representations (Elbro & Peterson, 1998). The double-deficit hypothesis acknowledges the phonological awareness deficit of dyslexic children but stresses a deficit in naming speed as a second and equally important cause of reading difficulties. The first demonstration that dyslexic children show impaired naming speed was provided by Denckla and Rudel (1976), whose Rapid Automatized Naming (RAN) Test became the standard assessment of naming speed. In the RAN test, a large array of repeatedly presented, well-known visual patterns (pictured objects, color patches, digits) has to be named as quickly as possible. Wolf, Bally, and Morris (1986) were the In:st to show that early differences in rapid naming are predictive of later reading difficulties. The double-deficit hypothesis is based on findings (reviewed by Wolf & Bowers, 1999) showing that, typically, there are only modest correlations between phonological awareness measures and RAN performance in groups of dyslexic children and that dyslexic children as a group exhibit both phonological awareness deficits and naming-speed deficits. From these findings,

The relationship of phonemic awareness to reading acquisition: More consequence than precondition but still important ☆

Three studies examined the presence of phonemic awareness among Austrian children before reading instruction and its relationship to concurrent and later reading. These children were about 6-7 years of age but in the majority of cases unable to read when they entered school. Testing phonemic awareness with a newly developed, rather simple and natural vowel substitution task revealed that many children showed not a single correct response or little success. In contrast, the few readers at the beginning of grade one exhibited high phonemic awareness and after a few months of reading instruction most of the children scored at least close to perfect in the vowel substitution task. Despite this apparent effect of reading on phonemic awareness there was a specific predictive relationship between initial phonemic awareness differences and success in learning to read and to spell. In agreement with other studies it was found that phonemic awareness differences before instruction predicted the accuracy of alphabetic reading and spelling at the end of grade one independent from IQ and initial differences in letter knowledge and reading. However, closer examination of the relationship between phonemic awareness before instruction and later success in learning to read revealed a specific pattern. Children with high phonemic awareness at the beginning of grade one showed uniformly high reading and spelling achievement at the end of grade one. Such good progress in learning to read and to spell was also evident in the majority of children who showed no phonemic awareness at the beginning of reading instruction, but some of the many children with low phonemic awareness before instruction experienced difficulties in learning to read and to spell. This specific pattern suggests that individual differences in the ease or difficulty with which phonemic awareness can be induced by preschool experiences or by reading instruction is the critical variable underlying the observed correlations between phonemic awareness measures before reading instruction and progress in learning to read.

Dyslexia and dyscalculia: Two learning disorders with different cognitive profiles

This study tests the hypothesis that dyslexia and dyscalculia are associated with two largely independent cognitive deficits, namely a phonological deficit in the case of dyslexia and a deficit in the number module in the case of dyscalculia. In four groups of 8- to 10-year-olds (42 control, 21 dyslexic, 20 dyscalculic, and 26 dyslexic/dyscalculic), phonological awareness, phonological and visual-spatial short-term and working memory, naming speed, and basic number processing skills were assessed. A phonological deficit was found for both dyslexic groups, irrespective of additional arithmetic deficits, but not for the dyscalculia-only group. In contrast, deficits in processing of symbolic and nonsymbolic magnitudes were observed in both groups of dyscalculic children, irrespective of additional reading difficulties, but not in the dyslexia-only group. Cognitive deficits in the comorbid dyslexia/dyscalculia group were additive; that is, they resulted from the combination of two learning disorders. These findings suggest that dyslexia and dyscalculia have separable cognitive profiles, namely a phonological deficit in the case of dyslexia and a deficient number module in the case of dyscalculia.

Deficits in Phoneme Segmentation Are Not the Core Problem of Dyslexia: Evidence from German and English Children.

A widely held assumption about dyslexia is that difficulties in accessing the constituent phonemes of the speech stream are responsible for specific reading and spelling difficulties. In consistent orthographies, however, the acquisition of accurate phonological recoding and phonemic awareness was found to pose much less difficulty than in English, and even dyslexic children were found to exhibit high levels of performance in phonemic segmentation (Wimmer, 1993). Nevertheless, using a rather complex phonological awareness and manipulation task (spoonerisms: MAN–HAT → HAN–MAT), Landerl, Wimmer, and Frith (1997) found support for the original position on phonological awareness deficit, as both German and English dyslexic children showed poor performance. In the present studies, the spoonerism responses of Landerl et al. were reanalyzed such that children were given credit for partially correct responses (e.g., a response of HAN for MAN–HAT). Such partially correct responses were taken to indicate full segmentation of both stimulus words at the onset–rime level. The effect of this rescoring was that the error rate dropped from 76% to 26% for the English dyslexic children and from 63% to 15% for the German dyslexic children. Even higher performance levels, although not perfect as for the age-matched control children, were found on a nonword spelling task in both groups. A second study examined the segmentation of consonant clusters in younger German dyslexic children and found performance levels of about 90% correct when memory problems were ruled out. We argue that, at least in the context of a consistent orthography (and a phonics-based teaching approach), deficits in phoneme awareness are only evident in the early stages of reading acquisition, whereas rapid naming and phonological memory deficits are more persistent in dyslexic children.

Comorbidity of learning disorders: prevalence and familial transmission

BACKGROUND In order to fully specify the profiles of risk and protective factors of developmental disorders, a better understanding of the conditions under which they co-occur is required. So far, empirical evidence on comorbidities of specific learning disorders in arithmetic, reading and spelling is scarce. METHODS Prevalence and gender ratios of specific learning disorders in arithmetic (AD), reading (RD), and spelling (SD) and their co-occurrence were assessed in a large (N = 2586) population-based sample of elementary school children and in a subsample of 293 children with at least one learning disorder (LD-sample). A questionnaire on familial transmission was given to a subsample of 256 parents of children with a learning disorder and 146 typically developing children. RESULTS The rates of deficits in arithmetic, reading, or spelling were four to five times higher in samples already experiencing marked problems in one academic domain compared to the full population. Thus, comorbidity of learning disorders was confirmed in a fairly standard school population. Rates of co-occurrence decreased for AD and RD, but not isolated SD when more stringent cutoff criteria were applied, suggesting that the comorbidity of arithmetic and spelling disorder may be more strongly biologically mediated than the comorbidity of arithmetic and reading disorder. We found a preponderance of girls with AD and boys with SD. These imbalanced gender ratios were especially marked for isolated problems, while for comorbid problems gender ratios were mostly balanced with the exception of deficits in arithmetic and reading (but not spelling) which were more typical for girls. The parental questionnaire provided evidence for disorder-specific familial transmission and co-segregation of arithmetic and literacy deficits. CONCLUSIONS Comorbidities of learning disorders are not artificial. They are the result of a complex interplay between both general and disorder-specific aetiological factors.

Predictors of developmental dyslexia in European orthographies with varying complexity

BACKGROUND  The relationship between phoneme awareness, rapid automatized naming (RAN), verbal short-term/working memory (ST/WM) and diagnostic category is investigated in control and dyslexic children, and the extent to which this depends on orthographic complexity. METHODS General cognitive, phonological and literacy skills were tested in 1,138 control and 1,114 dyslexic children speaking six different languages spanning a large range of orthographic complexity (Finnish, Hungarian, German, Dutch, French, English). RESULTS Phoneme deletion and RAN were strong concurrent predictors of developmental dyslexia, while verbal ST/WM and general verbal abilities played a comparatively minor role. In logistic regression models, more participants were classified correctly when orthography was more complex. The impact of phoneme deletion and RAN-digits was stronger in complex than in less complex orthographies. CONCLUSIONS Findings are largely consistent with the literature on predictors of dyslexia and literacy skills, while uniquely demonstrating how orthographic complexity exacerbates some symptoms of dyslexia.

RAN Is Not a Measure of Orthographic Processing. Evidence From the Asymmetric German Orthography

In three large samples (N = 1248) of children learning to read German we investigated the correlations between rapid automatized naming (RAN), phonological awareness (PA), phonological decoding (nonword reading fluency), and orthographic processing (word reading fluency and spelling). In a series of hierarchical regression analyses, RAN explained more variance in word and nonword reading fluency than PA, whereas PA explained more variance in spelling than RAN. This pattern was confirmed when PA response times were assessed instead of response accuracy. Two further regression models challenge the view that the RAN-literacy association is mediated by orthographic processing. First, RAN accounts for unique variance in word reading fluency even when differences in orthographic spelling were introduced before RAN. Second, RAN accounts for hardly any variance in word reading fluency when introduced after nonword reading fluency.

Typical and atypical development of basic numerical skills in elementary school

Deficits in basic numerical processing have been identified as a central and potentially causal problem in developmental dyscalculia; however, so far not much is known about the typical and atypical development of such skills. This study assessed basic number skills cross-sectionally in 262 typically developing and 51 dyscalculic children in Grades 2, 3, and 4. Findings indicate that the efficiency of number processing improves over time and that dyscalculic children are generally less efficient than children with typical development. For children with typical arithmetic development, robust effects of numerical distance, size congruity, and compatibility of ten and unit digits in two-digit numbers could be identified as early as the end of Grade 2. Only the distance effect for comparing symbolic representations of numerosities changed developmentally. Dyscalculic children did not show a size congruity effect but showed a more marked compatibility effect for two-digit numbers. We did not find strong evidence that dyscalculic children process numbers qualitatively differently from children with typical arithmetic development.