The Routledge Companion to Dyslexia

Gavin Reid, Gavin Reid

• Publisher: Routledge
• Year: 2012
• ISBN:
  9781136617102
• Edition: 1
• Topic: Didattica
• Subtopic: Didattica generale

The Routledge Companion to Dyslexia is a ground-breaking analysis of the whole field of dyslexia by a distinguished team of international contributors and editors, engaged in literacy, inclusion and learning. Their diverse perspectives and wide expertise make this invaluable guide one of the most important additions to the field of dyslexia for over a decade.

Dyslexia is without doubt the most high profile and contentious learning difficulty, and it is a topic that has attracted a vast amount of research, opinion, professional schisms, and debate. The Companion provides an invaluable overview of the field of dyslexia with vital and clear emphasis on linking theoretical perspectives with best practice. This accessible text:

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• presents a survey of current and future development in research, with a focus on how research can inform practice

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• focuses on areas such as neurobiology, phonological processing, literacy acquisition, numeracy and multilingualism

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• considers assessment and identification, with contributions on early identification, reading, spelling and mathematics

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• addresses identifying and meeting needs in an inclusive context

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• discusses inclusion and barriers to learning in a variety of different national contexts

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• includes models of instruction, direct instruction, co-operative learning and cross-curricular learning.

The Routledge Companion to Dyslexia is a superb resource for anyone interested in the subject, whether in education or related subjects such as psychology or neurology. Fully indexed and cross-referenced, with helpful further reading sections at the end of each entry, it is ideal for those coming to the field of dyslexia for the first time as well as students and practitioners already familiar with the subject.

Part 1

Research: current and future developments

1

Dyslexia

An overview of recent research

John Everatt and Gavin Reid

This chapter

discusses the significant recent advances in our understanding of dyslexia

discusses the findings and the implications of the main research areas – neurological, cognitive and educational in the field of dyslexia

comments on the implications for intervention

shows how the different research areas are inter-related.

Background

There have been significant advances in research in dyslexia over the last twenty years. This has aided explanations of dyslexia and supported policy and practice. The impact has been considerable, but yet there is still no clear explanation that is universally accepted of what exactly constitutes dyslexia. Identification is still riddled with controversies despite the emergence of a number of new tests to identify dyslexia, or sub-components of dyslexia. Indeed, there is still an ongoing debate on the value of dyslexia as an identifiable syndrome (see discussions in this book). In order to provide a background for the work on dyslexia and the topics covered in this book, this chapter will discuss some of the main areas of research, with an emphasis on those currently receiving most attention, and comment on these in relation to the breadth, span and purpose of this book.

Neurobiological factors

The advances in MRI and other forms of brain imagery have been of great benefit to neuroscientists investigating factors relating to dyslexia. From these studies a number of different factors have emerged focusing on structural and functional brain-related factors. Some of these will be discussed here.

Processing speed

Breznitz (2008) presents the ‘Asynchrony Phenomenon’ as a means of explaining dyslexia. This implies that dyslexia is caused by a speed of processing gap within and between the various entities taking part in the word decoding process. Breznitz and colleagues devised a programme that attempted to train the brain to process information at a faster speed. Implementing this programme resulted in a substantial improvement among dyslexic children in the speed at which information was processed (Breznitz 2008). They also suggested that this improvement was successfully transferred to other material not included in the training program.

Breznitz (2008) also claims that dyslexic learners exhibit difficulties when transferring information from one hemisphere to another. These differences in inter-hemisphere transfer among dyslexics may stem from information decay in the corpus collosum, or a long non-symmetrical delay in inter-hemisphere transfer time. Shaul and Breznitz (2007) measured information transfer between the left and right hemispheres among dyslexics as compared to regular readers when performing various lexical decision tasks. They found that information arrived among dyslexics in the right hemisphere, at first, and was then transferred approximately 9 to 12ms later to the left hemisphere. Among regular readers, the information arrived in the left hemisphere first and was transferred to the right approximately 4 to 6ms later. They also supported these results from source localization of brain activity in these two reading groups during the word decoding process using Low Resolution Electromagnetic Tomography (LORETA). Comparisons between groups revealed greater activation among dyslexic readers between 110 and 140ms for words, mainly in the right temporal and perisylvian regions, as well as some activation in medial frontal regions. These findings can have significant implications for the classroom particularly in how information is presented and the pace of lessons in class.

Temporal processing

Stein (2008) argues that there is genetic, sensory, motor and psychological evidence that dyslexia is a neurological syndrome affecting the development of the brain. He also provides evidence that the development of magnocellular neurones is impaired in children with dyslexia. Stein argues that the visual system provides the main input to both the lexical and the sublexical routes for reading and therefore vision should be seen as the most important sense for reading. This view however is strongly disputed by many because they believe that acquisition of phonological skills is in fact much more crucial for successful reading (Vellutino, Fletcher et al., 2004).

One of the main discoveries about the visual system made over the least 25 years according to Stein is that the different qualities of visual targets are analysed, not one after the other in series, but by separate, parallel pathways that work simultaneously moving forwards in the visual brain. Stein shows that there are two main kinds of retinal ganglion cell, whose axons project all the visual information back to the brain. Ten per cent of these are known as mangocellular cells because they are noticeably larger than the others and cover 50 times greater an area than those of the much more numerous, but much smaller, parvocells. He therefore suggests that the great variety of visual, phonological, kinaesthetic, sequencing, memory and motor symptoms that are seen in different dyslexics may arise from differences in the particular magnocellular systems that are most affected by the particular mix that each individual dyslexic inherits. This highlights the individual differences within dyslexia as well as the role of the competing or indeed complimentary theories that constitute dyslexia.

Stein (2008) argues that the most important influence in dyslexia appears to be heredity. He suggests that genetic factors likely affect the developmental migration of magnocells in utero and influence their subsequent function. Familial risk is also a useful indicator of dyslexia and is supported by prevalence rates (Molfese et al., 2008). Advances during the last 20 years in the field of genetics research have brought the search for the underlying genetic basis of dyslexia to the fore (Fisher and DeFries, 2002). Innovations in neuro-imaging techniques have also driven the search for a neurobiological basis to dyslexia (Lyytinen et al., 2005). These factors help to provide a number of plausible explanations for dyslexia and in some cases can point the way to intervention.

Procedural timing

The lateral zone of the cerebellum is an area that has generated interest over its apparent role in cognitive processes and for recent theoretical positions that argue for its relationship with dyslexia. In terms of its formation, the cerebellum is one of the first brain structures to begin to differentiate, yet it is one of the last to achieve maturity as the cellular organization of the cerebellum continues to change for many months after birth. According to Fawcett and Nicolson (2008) there is now extensive evidence that the cerebellum is a brain structure particularly susceptible to insult in the case of premature birth, and that such insults can lead to a range of motor, language and cognitive problems subsequently. Fawcett and Nicolson (2008) argue that the cerebellar deficit hypothesis may provide close to a single coherent explanation of the three criterial difficulties in dyslexia – reading, writing and spelling. They argue this can place dyslexia research within a meaningful context in terms of the cognitive neuroscience of learning while maintaining its position as a key educational issue. They also suggest the cerebellur deficit hypothesis provides an explanation for the overlapping factors between dyslexia and the other developmental disorders (an area that will be returned to later in this chapter).

One of the hypothesized functions of the cerebellum is in the precise timing of procedures (e.g., several motor movements) that accomplish some sort of behavioural response or task performance. This timing of sequences may play a critical role in making task accomplishment or behavioural skills automatic. Indeed, a critical aspect of learning a skill may be to make its accomplishment automatic. This means that the skill can be carried out without the individual giving it too much thought – and resources can be used to undertake other behaviours or processes. For most adults and children, the ability to walk, talk and possibly read and write may be partially or completely automatic. Consequently Fawcett and Nicolson (2008) put forward the hypothesis that dyslexic children would have difficulty in automatizing any skill (cognitive or motor). They suggest that reading is subject to automaticity and since all dyslexia hypotheses predict poor reading as a factor in dyslexia then the automatisation deficit hypothesis would be valid in relation to dyslexia. Fawcett (1989) and Fawcett and Nicolson (1992) argue that there is clear support stemming from a set of experiments in which they asked dyslexic children to do two things at once. If a skill is automatic, then the children should have been able to do two tasks at the same time. These findings strongly suggested that dyslexic children were not automatic, even at the fundamental skill of balance. For some reason, dyslexic children had difficulty automatizing skills, and had therefore to concentrate harder to achieve normal levels of performance. This has clear implications for teaching and learning in that in the classroom there will be a significant need for over-learning to be utilized with children with dyslexia.

Cognitive Processes

Researchers/theorists who concentrate on the processes that go into reading and writing typically look at these from a cognitive perspective, although many of the ideas related to cognitive theories of dyslexia also consider neurological factors and hence there is often overlap between these two general areas. For example, automaticity can be considered from the point of view of a process in learning or as a function of a particular brain area (as in the arguments of Fawcett and Nicolson, 2008). Speed of processing can be seen as an aspect of cognition (as in the views of Wolf and colleagues: Wolf and Bowers, 2000; Wolf and O’Brien, 2001) or of brain transmission (as in the views of Breznitz, 2008 and Stein, 2008, discussed above). Of the cognitive focused research that looks at processing factors, work on memory and learning may be considered as the most likely to link research with classroom practices, with a fair number of recent work either directly or indirectly relating findings to intervention (see discussions in Singleton, 2008). For example, work on cognitive style links to learning style in classrooms (Entwistle, 1981; Given and Reid, 1999; Riding and Cheema, 1991; Schmeck, 1988) and multisensory teaching methods have often been linked to the way information is stored in memory (Broomfield and Combley, 1997; Clark and Uhry, 1995). Similarly, Working Memory research has begun to inform ideas about special educational needs (Gathercole and Pickering, 2000; Jeffries and Everatt, 2004) and meta-cognitive work has focused on strategies for learning. However, perhaps the area that has linked most clearly to the teaching of literacy has been the work related to language processes.

Phonological deficit viewpoints

At present, the dominant causal viewpoint about dyslexia is the phonological deficit hypothesis. This perspective has been derived from the substantial evidence that difficulties in phonological processing, particularly when related to phonological decoding, have been a major distinguishing factor between dyslexics and non-dyslexics from early literacy learning to adulthood (see Beaton et al., 1997; Bruck, 1993; Elbro et al., 1994; Rack et al., 1992; Snowling, 2000; Stanovich, 1988) and that early phonological training (together with suitable linkage to orthography and literacy experience) improves word literacy and reduces the likelihood of literacy difficulties (see Bryant and Bradley, 1985; Cunningham, 1990; Elbro et al., 1996; Olofsson and Lundberg, 1985; Schneider et al., 1997). Children who find it difficult to distinguish sounds within verbally presented words would be predicted to have problems learning the alphabetic principle that letters represent sounds and, hence, should be those children who are most likely to be dyslexic based on the phonological deficit position. If this causal linkage is correct, then the manifestation of dyslexia may vary across languages, since languages vary in the way their orthography represents phonology. Therefore, recent research has attempted to investigate the manifestation of dyslexia across languages to assess the universality of the phonological position as well as to inform international assessment practices.

Orthographic transparency

In some languages, orthography represents phonology relatively simply: there is a close correspondence between the written symbol (grapheme) and the basic sound (or phoneme) that it represents. In other orthographies, this correspondence is less transparent. In these languages, a letter may represent several sounds and a sound may be represented by different letters. The English orthography is the best example of this less than transparent relationship between letters and sounds: consider ‘t’ in ‘thus’ versus ‘talk’, or ‘c’ in ‘chord’ versus ‘chore’ or even ‘receive’. There are many English words that may be considered irregular or exceptions based on the typically taught correspondence between graphemes and phonemes (e.g., ‘have’, ‘said’, ‘pint’, ‘monk’, ‘yacht’). However, this level of divergence from the alphabetic principle (see Adams, 1990; Gillon, 2004) is not universal. Although most languages have some peculiarities, or complexities, in the relationship between graphemes and phonemes, most have rules that connect letters with pronunciation that are more consistent and, potentially, simpler to learn than is the case for English. Indeed, the peculiarities of the English orthography has led some theorists in the field to view English as a ‘dyslexic’ orthography (Spencer, 2000) or, perhaps less controversially, as an outlier in comparison to other alphabetic-type orthographies (Share, 2008).

Dyslexia in different languages

The potenti...