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.     

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.     

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.     

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.     

Nonlinear growth curves in developmental research

Developmentalists are often interested in understanding change processes, and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and asymptotic levels can be estimated. A variety of growth models are described beginning with the linear growth model and moving to nonlinear models of varying complexity. A detailed discussion of nonlinear models is provided, highlighting the added insights into complex developmental processes associated with their use. A collection of growth models are fit to repeated measures of height from participants of the Berkeley Growth and Guidance Studies from early childhood through adulthood.     

Evolutionary developmental psychology

Evolutionary developmental psychology is the study of the genetic and ecological mechanisms that govern the development of social and cognitive competencies common to all human beings and the epigenetic (gene-environment interactions) processes that adapt these competencies to local conditions. The basic assumptions and domains of this emerging field, as related to human life history and social and cognitive development, are outlined, as are implications for issues of importance in contemporary society.     

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.     

Reading strategies in Spanish developmental dyslexics

Cross-linguistic studies suggest that the orthographic system determines the reading performance of dyslexic children. In opaque orthographies, the fundamental feature of developmental dyslexia is difficulty in reading accuracy, whereas slower reading speed is more common in transparent orthographies. The aim of the current study was to examine the extent to which different variables of words affect reaction times and articulation times in developmental dyslexics. A group of 19 developmental dyslexics of different ages and an age-matched group of 19 children without reading disabilities completed a word naming task. The children were asked to read 100 nouns that differed in length, frequency, age of acquisition, imageability, and orthographic neighborhood. The stimuli were presented on a laptop computer, and the responses were recorded using DMDX software. We conducted analyses of mixed-effects models to determine which variables influenced reading times in dyslexic children. We found that word naming skills in dyslexic children are affected predominantly by length, while in non-dyslexics children the principal variable is the age of acquisition, a lexical variable. These findings suggest that Spanish-speaking developmental dyslexics use a sublexical procedure for reading words, which is reflected in slower speed when reading long words. In contrast, normal children use a lexical strategy, which is frequently observed in readers of opaque languages.     

Teaching concepts versus facts in developmental biology

Note from the Editor     

Complex dynamics in academics' developmental processes in teaching

Improving teaching in higher education is a concern for universities worldwide. This study explored academics’ developmental processes in teaching using episodic interviews and teaching portfolios. Eight academics in the context of teaching development reported changes in their teaching and change triggers. Thematic analyses revealed seven areas of change: participants most frequently reported changes in concepts about teaching, their teaching selves and teaching strategies. Triggers of change clustered into eight categories with teaching practices, teaching courses and metacognition reported most frequently. Analysing relations among areas and triggers of change indicated complex dynamics in academics' developmental processes in teaching. This suggests that teaching development should incorporate multiple change triggers to facilitate academics' development in teaching effectively.     

The missing dimension in developmental biology education

Note from the Editor     

Lexical stress assignment in Italian developmental dyslexia

Stress assignment to Italian polysyllabic words is unpredictable, because stress is neither marked nor predicted by rule. Stress assignment, especially to low frequency words, has been reported to be a function of stress dominance and stress neighbourhood. Two experiments investigate stress assignment in sixth-grade, skilled and dyslexic, readers. In Experiment 1, skilled readers were not affected by stress dominance. Dyslexic children, although affected by word frequency, made more stress regularisation errors on low frequency words. In Experiment 2, stress neighbourhood affected low frequency word reading irrespective of stress dominance for both skilled and dyslexic readers. Words with many stress friends were read more accurately than words with many stress enemies. It is concluded that, in assigning stress, typically developing and developmental dyslexic Italian readers are sensitive to the distributional properties of the language.     

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.