Anne Castles

Varieties of developmental dyslexia

This paper reviews and evaluates the evidence for the existence of distinct varieties of developmental dyslexia, analogous to those found in the acquired dyslexic population. Models of the normal adult reading process and of the development of reading in children are used to provide a framework for considering the issues. Data from a large-sample study of the reading patterns of developmental dyslexics are then reported. The lexical and sublexical reading skills of 56 developmental dyslexics were assessed through close comparison with the skills of 56 normally developing readers. The results indicate that there are at least two varieties of developmental dyslexia, the first of which is characterised by a specific difficulty using the lexical procedure, and the second by a difficulty using the sublexical procedure. These subtypes are apparently not rare, but are relatively prevalent in the developmental dyslexic population. The results of a second experiment, which suggest that neither of these reading patterns can be accounted for in terms of a general language disorder, are then reported.

Is there a causal link from phonological awareness to success in learning to read

In this review, we re-assess the evidence that phonological awareness represents a skill specific to spoken language that precedes and directly influences the process of reading acquisition. Longitudinal and experimental training studies are examined in detail, as these are considered most appropriate for exploring a causal hypothesis of this nature. A particular focus of our analysis is the degree to which studies to date have controlled for existing literacy skills in their participants and the influence that these skills might have on performance on phonological awareness tasks. We conclude that no study has provided unequivocal evidence that there is a causal link from competence in phonological awareness to success in reading and spelling acquisition. However, we believe that such a study is possible and outline some ideas for its design and implementation.

Word recognition development in children : insights from masked-priming

Preface. Section 1: Mechanisms. The Mechanics of Masked Priming Kenneth I. Forster, Kathleen Mohan & Jo Hector. An Abstractionist Account of Masked and Long-Term Priming Jeffrey Bowers. A Retrospective View of Masked Priming: Toward a Unified Account of Masked and Long-Term Repetition Priming Michael E.J. Masson & Glen E. Bodner. Section 2: Orthographics Effects. Transposed-Letter Confusability Effects in Masked Form Priming Manuel Perea & Stephen J. Lupker. Factors Underlying Masked Priming Effects in Competitive Network Models of Visual Word Recognition Colin J. Davis Section 3: Phonological Effects. The Robustness of Phonological Effects in Fast Priming Ram Frost. Dissociating Automatic Orthographic and Phonological Codes in Lexical Access and Lexical Acquisition Michael B. Johnston & Anne E. Castles The Nature of Masked Onset Priming Effect in Naming: A Review Sachiko Kinoshita. Section 4: Morphological Effects. Racehorses, Reindeers and Sparrows: Using Masked Priming to Investigate Morphological Influences on Compound Word Identification Natalie Shoolman and Sally Andrews. Reading Morphologically-Complex Words: Some Thoughts from Masked Priming Kathleen Rastle and Matthew H. Davis. Section 5: Masked Priming in Special Populations. Masked Priming Across Languages: An Insight into Bilingual Lexical Processing Chris Davis, Jeesun Kim & Rosa Sanchez-Casas Bilingual Visual Word Recognition: Evidence from Masked Phonological Priming Marc Brysbaert Word Recognition Development in Children: Insights from Masked-Priming Anne Castles, Chris Davis & Kenneth I. Forster

Cognitive Correlates of Developmental Surface Dyslexia: A Single Case Study

Recently, there have been several reports of developmental analogues of the specific orthographic processing deficits observed in acquired surface dyslexics (Goulandris & Snow ling, 1991; Hanley, Hastie, & Kay, 1992). How ever, very little has been discovered about w hat basic cognitive deficits might be associated w ith this particular kind of reading disorder. This paper describes the case of MI, a 10-year-old boy w ith a high IQ and no known history of neurological impairment. He demonstrates extremely poor performance for his age and reading level on irregular word reading tasks, but performs normally on nonword and regular word tasks. His performance on a series of homophone selection tasks suggests an impairment at the orthographic input level. The results of various tests of associated cognitive abilities conducted on MI suggest that this impairment is not associated either with phonological awareness deficits or with the visual memory problems proposed by Goulandris and Snowling (1991).

Can contrast sensitivity functions in dyslexia be explained by inattention rather than a magnocellular deficit

We examined whether data demonstrating contrast sensitivity losses in dyslexia that have been interpreted as evidence for loss of magnocellular visual function could be explained by inattention. Computer simulations of observers with poor concentration yielded inflated estimates of threshold that were a constant proportion of the true threshold across spatial frequencies. Data from many, but not all, studies supporting the magnocellular deficit theory are well described by these simulations, which predicted no interaction between observer group and spatial frequency. Some studies have reported significant interactions, but suffer from statistical deficiencies. This compromises some of the evidence for a magnocellular deficit in dyslexia derived from studies of threshold contrast sensitivity.

A Haplotype Spanning KIAA0319 and TTRAP Is Associated with Normal Variation in Reading and Spelling Ability

BACKGROUND KIAA0319 (6p22.2) has recently been implicated as a susceptibility gene for dyslexia. We aimed to find further support for this gene by examining its association with reading and spelling ability in adolescent twins and their siblings unselected for dyslexia. METHODS Ten single nucleotide polymorphisms (SNPs) in or near the KIAA0319 gene were typed in 440 families with up to five offspring who had been tested on reading and spelling tasks. Family-based association analyses were performed, including a univariate analysis of the principal component reading and spelling score derived from the Components of Reading Examination (CORE) test battery and a bivariate analysis of whole-word reading tests measured in a slightly larger sample. RESULTS Significant association with rs2143340 (TTRAP) and rs6935076 (KIAA0319) and with a three-SNP haplotype spanning KIAA0319 and TTRAP was observed. The association with rs2143340 was found in both analyses, although the effect was in the opposite direction to that previously reported. The effect of rs6935076 on the principal component was in the same direction as past findings. Two of the three significant individual haplotypes showed effects in the opposite direction to the two prior reports. CONCLUSIONS These results suggest that a multilocus effect in or near KIAA0319 may influence variation in reading ability.

How does orthographic knowledge influence performance on phonological awareness tasks

Three experiments explored the nature of orthographic influences on performance on phonological awareness tasks. Experiment 1 demonstrated that adults find it easier to perform phoneme deletions on items where there is a direct correspondence between letters and target sounds (e.g., take the /r[se text]/ from struggle) than where there is not (e.g., take the /w[see text]/ from squabble). Analogous results were found in a phoneme reversal task. Spelling production ability tended to correlate more strongly with performance on the former type of item than on the latter, suggesting that elevated performance on phonological awareness tasks is associated with the use of orthographic information. Experiment 2 produced similar results in Grade 5 children. Experiment 3 suggested that adults cannot inhibit orthographic activation when it is disadvantageous to them, as they performed no better on items such as squabble when they were presented in pure blocks than when they were presented in mixed blocks. It is concluded that there are substantial automatic orthographic influences on phonological awareness task performance that need to be taken into account in interpreting data concerning the relationship between phonological awareness and reading.

Contrast sensitivity in subgroups of developmental dyslexia

It has been proposed that developmental dyslexia is associated with a deficit in the magnocellular pathway of the visual system. Other research focuses upon the heterogeneous nature of developmental dyslexia, and evidence that subgroups of dyslexia may be identified based on selective deficits in specific component reading skills. This study tested the hypothesis that visual processing deficits may be present in different subgroups of developmental dyslexia by comparing the visual contrast sensitivity of three subgroups of dyslexic children (phonological, surface and mixed) and controls. The stimulus designed to measure magnocellular visual function was a low spatial frequency Gaussian blob, flickered sinusoidally at a temporal frequency of 8.33 Hz. The control stimulus, designed to measure parvocellular visual function, was a relatively high spatial frequency Gaussian windowed grating (8 c/deg) slowly ramped on and off. There were no significant differences between the groups of dyslexic and control children in contrast sensitivity to either stimulus. The findings do not support the existence of a magnocellular system deficit in dyslexia.

John Marshall and the developmental dyslexias

Background: In 1984, John Marshall made the case that one can use a model of the skilled reading system not only to interpret the acquired dyslexias, but also to interpret the developmental dyslexias, and the particular model of the skilled reading system he favoured for this purpose was the dual-route model. This claim has been a controversial one, with many researchers claiming that static models of adult skilled reading, such as the dual-route model, are inappropriate for understanding the process of reading development and, consequently, the developmental reading disorders. Aims: In this paper, we examine how Marshalls conjecture has fared over the past 20 years. Main Contribution: We evaluate Marshalls conjecture by examining evidence for developmental analogues of acquired surface and phonological dyslexia, by reporting new data on cases of “pure” developmental surface and phonological dyslexia, and by assessing the success of dual route versus connectionist accounts of these subtypes. We also report evidence that the dual-route model of skilled reading provides an accurate account of the reading performance of children at all stages of reading development. Conclusion: We conclude that Marshalls controversial claim has been vindicated by subsequent research.

Assessing the basic components of reading: A revision of the Castles and Coltheart test with new norms

We present administration details and normative data for a new version of the word and nonword reading test originally developed by Castles and Coltheart. The new test contains an expanded set of items, with 40 each of regular words, irregular words and nonwords, rather than the original 30 items of each type. The new items extend the upper-end of the difficulty range of the test, making it less susceptible to ceiling effects than the original version. The test also incorporates a stopping-rule, which makes administration of the test less time-consuming and removes the stress on children who can only read a few items. The test is free of charge and is available to teachers, professionals and researchers in both pencil-and-paper and computer-based formats from the Macquarie On-line Test Interface (MOTIF: http://www.maccs.mq.edu.au/research/resources).