Dyslexia North West & Red Rose School

Biological and Cognitive Dimensions Current Scientific Thinking by Gavin Reid


In recent years the field of dyslexia has undergone significant change accompanied by considerable scientific end educational research. Research has focused on a number of different dimensions including biological, cognitive and educational factors. This presentation will describe some of these developments and comment on the impact they may have on teachers, schools end the dyslexic student.


When undertaking staff development in the area of dyslexia, the question one is most often asked is simply- 'what is dyslexia'. While there are a number of definitions of dyslexia currently used, many of these are not entirely helpful to the class teacher or indeed parents. The class teacher is essentially asking for a working plan - not necessarily a definition - that is the cluster of difficulties, range of severity, examples of the difficulty, teaching suggestions and sources of further help in relation to dyslexic.

The parent wants a straight forward explanation of dyslexia and some guidance regarding the most appropriate methods end provision which might ensure the dyslexic young person reaches their potential.

One of the factors regarding definitions and indeed identifying appropriate intervention is that dyslexic children are first and foremost individuals, and while they may share some common difficulties there are individual differences present.

British Dyslexia Association - Definition

The British Dyslexia Association suggests a broad definition which clearly displays the range of difficulties which can be experienced by dyslexic people. This is described by Peer (1999) "as a combination of abilities and difficulties which effect the learning process in one or more of reading, spelling and writing. Accompanying weaknesses may be identified in areas of speed of processing, short-term memory, sequencing, auditory and/or visual perception, spoken language and motor skills. It is particularly related to mastering and using written language, which may include alphabetic, numeric and musical notation" ( Peer 1999 pg. 61).

The Adult Dyslexia Association - Definition

The Adult Dyslexic Organisation, propose that "dyslexia may be caused by a combination of phonological, visual and auditory processing deficits. Word retrieval and speed of processing difficulties may also be present. A number of possible underlying biological causes of these cognitive deficits have been identified and it is probable that in any one individual there may be several causes. Whilst the dyslexic individual may experience difficulties in the acquisition of reading, writing and spelling they can be taught strategies and alternative learning methods to overcome most of these end other difficulties. Every dyslexic person is different and should be treated as an individual. Many show talents actively sought by employers and the same factors that cause, literacy difficulties may also be responsible for highlighting positive attributes - such at problem solving which can tap resources which lead to more originality end creativity". (Schloss 1999).

Individual Differences - Skills

These definitions essentially support the view that dyslexia relates to a broad range of difficulties associated with literacy and learning, that individual differences will be present and that some students with dyslexic can have positive attributes and that any difficulties are only port of the overall picture. These two definitions highlight the key areas of difficulties often experienced by dyslexic children and adults. One can note that these describe a range of difficulties and these are not only in the area of reading or spelling. At the same time it is important to appreciate that in spite of their dyslexic difficulties many children and young people show considerable competence in some areas and achieve well at school, and in further and higher education. Indeed, many of the skills displayed by people with dyslexic, for example visual and problem solving skills are actively sought by employers.

One of the reasons why children with dyslexia have literacy difficulties is because reading accuracy, phonological awareness, sequencing and other literacy activities are essentially left hemisphere tasks. Research has shown that many dyslexic individuals have a stronger right hemisphere than left. This means that right hemisphere tasks such as problem solving, holistic thinking, visual and musical skills are more readily accessed by dyslexic people than the left hemisphere analytical and detailed tasks such as reading, phonics and sequencing. This highlights the view proposed by many in the field, particularly those of Tom West author of 'In the Mind's Eye, Visual Thinkers, Creative People with Learning Difficulties, Computer Images and the Ironies of Creativity'. West's book highlights the positive attributes displayed by some dyslexic people such as problem solving, visual processing and musical abilities all of which can top resources which can lead to more originality and creativity.

U.K Investigation

A recent U.K. working party report on Dyslexia, Literacy and Psychological Assessment (BPS 1999) opted for a working definition of dyslexia because they felt that a working definition did not require any causal explanation. The working definition they opted for was as follows;
"Dyslexia is evident when accurate and fluent word reading and/or spelling develops very incompletely or with great difficulty" (BPS pg. 18).

While this provides the teacher with a starting point it does requires further explanation. In fact the report goes on to suggests a number of hypotheses which can be associated with dyslexia which include; Phonological Deficit Hypothesis; Temporal Processing Hypothesis: Skill Automatisation Hypothesis; Working Memory Hypothesis; Visual Processing Hypothesis; syndrome Hypothesis; Intelligence and Cognitive Profiles Hypothesis; Subtype Hypothesis; Learning Opportunities Hypothesis and Emotional Factors Hypothesis.

These hypotheses each refer to different or overlapping theoretical approaches expounded by academic researchers to explain dyslexia from a causal perspective. The authors of the report suggest that the phonological deficit hypothesis provides the main focus because of the "broad empirical support that it commands" (pg. 44) and because of the impact of phonology on the other hypothesis, particularly temporal order hypothesis, skill automatisation and the syndrome hypothesis. This view is supported by Snowling (2000) who suggests that although dyslexia can manifest itself in many ways there may be a single cause - a phonological deficit. She asserts this is the 'proximal cause of dyslexia' (pg138).

It is important therefore that teachers obtain a practical working plan. Yet due to the nature of dyslexia and its associated difficulties and the range of research studies and views it is also advisable that teachers obtain some theoretical background to allow them to understand the nature of the difficulties and how these may influence actual classroom approaches.

Biological Dimensions

Genetic Factors

There has been considerable efforts to identify the genetic basis for dyslexic. Gilger, Pennnington and DeFries (1991) estimate that the risk of a son being dyslexic if he has a dyslexic father is about 40%. Much of this work has been focused on the heritability of reading sub-skills and particularly the phonological component. Castles, Datto, Gayan and Olson (1999) found a strong heritability element among 'phonological dyslexics' and Olson, Forsberg, Wise and Rock (1994) found also a strong heritability component both for phonological decoding and orthographic skills.

Gene markers for dyslexia have been found in chromosome 15 (Smith, Kimberling, Pennington and Lubs 1983) and more recently in chromosome 6 (Fisher et.al 1999). Stein and Monaco (1998) suggest they may have found a possible site of dyslexic genes in chromosome 6 and significantly they may be in the same region as the genes implicated in auto immune diseases that have been reported to show a high level of association with dyslexia (Snowling 2000). In a longnitudinal study Gallagher, Frith and Snowling 2000) found at age six more than half of the at risk group scored below average compared to a control group on literacy tasks. Clearly therefore genetic factors are associated with dyslexia and this of course can lead to early identification or at least some very early warning of a child being at risk of having dyslexic.

Neurological factors

New technology such as positron emission tomography (PET) and magnetic resonance imaging (MRI) are increasingly being used to observe the active processes within the brain as well as the structure. As a result studies have shown that in phonological and short-term memory tasks the dyslexic sample displayed less activation across the left hemishere than the control group. Brunswick, McCrory, Price, Frith and Frith (1999) reported that the PET scans of young dyslexic adults while reading aloud and word and non-word recognition tasks showed less activation than controls in the left posterior temporal cortex. These findings suggest that there may be processing differences indicating some deficits in left hemisphere processing among children and adults with dyslexia.

Hemispheric Symmetry

According to earlier influential research (Geschwind and Galaburda 1985) these difference are due to structural differences, between the hemispheres and this, likely develops in the prenatal period. This view has received considerable support and a study by Leppanen, Pihko, Ekland and Lyytinen (1999) reported that at birth children at genetic risk of dylexia show different patterns of brain activity compared to a control group.

This can have implication's for teaching and learning to read. Bakker (1994), proposes a 'balance model' of reading which has, been replicated in different countries (Robertson 1997). Bakker identifies different types of readers - 'perceptual' and 'linguistic' each with a different hemispheric preference and each having implications for teaching. The perceptual has a right hemisphere processing style and may have good comprehension but poor reading accuracy. On the other hand the 'linguistic' reader utilises the left hemisphere and reads accurately but in some cases may be over-reliant on the left hemisphere and may not show the comprehension level of the 'Perceptual' reader.

Wood (2000) suggests that reading is concerned with translating stimuli across all modalities and that fluency is the key factor in reading acquisition. He cites the role of the visual cortex in reading which he asserts is multi-modal as it will accept input from both auditory and visual modalities. The brain he argues is high in visual-spatial skills and this also aids the understanding of information with high phonetic complexity. Since reading is essentially mapping across modalities according, to Wood, then alternative languages such as music and visual graphics are helpful. In short Wood suggests that our brains are better equipped for reading and more adaptable than we have given them credit for.

Visual Factors

There is also evidence of visual factors relating to dyslexic. Eden et al (1996) show how dyslexic children can have abnormalities associated with the magno-cellular sub-system of the visual cortex, this is reported in detail by Everatt (2002) who supports the view that visual factors are influential in assessment and intervention for dyslexia. Stein (1994) has highlighted convergence difficulties and binocular instability and Wilkins (1995) has shown how some dyslexic children and adults may benefit from coloured overlays due to difficulties in some visual processes.

Cognitive and processing dimensions

While the teacher may be limited in dealing with the deficits discussed above in relation to biological factors associated with dyslexia much can be done to improve the processing skills of dyslexic students and particularly their phonological skills.

Phonological processing

Hogtvet (1997) in a Norwegian study showed that a phonological deficit at age six was the strongest predictor of reading difficulties. Other studies have shown speech rate to be a strong predictor of dyslexic difficulties and this is reflected in the development of the Phonological Abilities Test (Muter, Hulme and Snowling (1997)).

Wolf (1996) highlights the 'double deficit' hypothesis indicating that dyslexics can have difficulties with both phonological processing and naming speed. It is interesting that speed of processing and semantic fluency are included in some of the popular tests for dyslexic children. Badian (1997) in a further study shows evidence for a triple deficit hypotheses implying that orthographic factors involving visual skills should also be considered.


The role of metacognition in learning is of great importance as this relates to the learner's awareness of thinking and learning. Tunmer and Chapman (1996) have shown how dyslexic children have poor metacognitive awareness and this leads them to adopt inappropriate learning behaviours in reading and spelling. Additionally the learning processes often used by students with dyslexia, which are often characterised by poor cognitive organisation, difficulty with retrieval and word generation, may suggest that study skills would be an appropriate intervention. This would also help to develop metacognitive awareness.


Similarly difficulties in automaticity (Fawcett and Nicolson (1992)) implies that dyslexic children may not readily consolidate new learning and therefore find it difficult to change inappropriate learning habits. Fawcett and Nicolson (1994) in fact propose the twin hypothesis that dyslexic children incur both Dyslexic Automatisation Deficit and Conscious Compensation Hypothesis. This means not only do they have difficulty in acquiring automaticity but in many cases they are able to mask this deficit by working harder, but deficits will still be noted in situations where compensation is not possible.

Motor factors

Motor integration programs have also been developed from research programs (Dobie (1998), Blythe (2001), McPhilip (2001)).

Nicholson and Fawcett, (1999) have shown how cerebellar impairment may be implicated with dyslexia viewed from a broader framework and may be involved in acquiring language dexterity as well as movement and balance. Factors such as postural stability, beads threading and naming speed are therefore represented in the Dyslexia Screening Test (Fawcett and Nicholson (1997). There has been many studies reporting on fine motor and gross motor difficulties experienced by dyslexic children (Augur (1985), Denckla (1985), Rudel (1985), Flory (2000), McCormick (2000)). Some of these relate to dyspraxia but it is likely that some of the approaches advocated for dyspraxic children can benefit dyslexic children who may have some motor difficulties. Similarly with dysgraphia, Stracher (2000) suggests that writing problems manifest themselves in three stages which, include motor factors relating to legibility, spelling difficulties and organising writing and syntactic structures. This pattern can also be seen in some dyslexic children.

Educational Factors

Phonological Awareness and Mutlisensory programs

In educational settings there has been considerable activity in the study of phonological awareness in relation to dyslexic. This is reflected in the development of assessment and teaching materials such as the Phonological Abilities Test (Muter, Hulme and Snowling 1997), the Phonological Assessment Battery (Fredrickson et.al. 1997) and many phonological teaching approaches such as Sound Linkage (Hatcher 1994), the Phonological Awareness Training program (Wilson 1993) and the Multisensory Teaching System for Reading (Johnston, Philips and Peer 1999). This particular area of research is highlighted because of its direct impact on teaching and classroom practices. The authors (Johnson, Philips and Peer 1999) conducted a research study into the use of the program and found, as well as the above, it also encourages independent learning and improves self-esteem.

Wise, Ring and Olson (1999) conducted a large scale study using different forms of remediation and found that the actual type of phonological awareness training was less important than the need to embed that training within a well structured and balanced approach to reading. Adams (1990) argues that combining phonological and 'whole language' approaches to reading should not be seen as incompatible. Indeed it is now well accepted that poor readers rely on context more than good readers (Nation and Snowling 1998). Language experience is therefore as vital to the dyslexic child than a structured phonological awareness program. This is particularly important in the secondary education sector where it may be inappropriate to provide a phonological based program for a dyslexic student, here the priority may be on language experience, print exposure and comprehension activities.

Right hemisphere processing

West (1997) has utilised Galaburda's research to show that dyslexic people who are right hemisphere processors can actually be at an advantage in some situations. This emphasises the positive side of dyslexia. Additionally West suggests that the transmission of knowledge and understanding is increasingly becoming visual and that those with well developed visual skills can be at an advantage in acquiring the visual language of knowledge.


Certainly in the U.K. it is encouraging that research is impacting on practice. Education Authorities policies on dyslexia, staff development, classroom based assessment, computer programs and curriculum materials focussing on differentiation all facilitate access to the full curriculum for dyslexic children. Early identification and early intervention are seen as priority areas and recent research and materials help to support this (Reid 1998, Reid 2001).

Concluding Comment

Research in Dyslexia can be viewed from different perspectives. It is important to recognise particularly the cognitive aspects of dyslexia because with timely end adequate intervention these can be dealt with effectively. Therefore the process of learning is of considerable importance. Despite the biological/neurological factors described in this paper much can be done to advance the literacy and learning skills of dyslexic students through the use of appropriate teaching programs, identifying the range of difficulties end acknowledging the strengths often shown by dyslexic students. Awareness of learning styles (Given and Reid 1999) and of metacognitive strategies which can enhance the learning process throughout the full curriculum is of great importance. Additionally significant breakthroughs have taken place with the development of a number of sophisticated assessment procedures and screening. The Dyslexia Screening Test can provide a detailed profile at an early age and highlight the possible presence of dyslexic difficulties (Fawcett and Nicholson 1996). Additionally Weedon and Reid (2001) have developed a group test for listening and literacy which can be used with a whole class at the same time with children aged between five and nine. Together these aspects of research, assessment end intervention provide a sound basis for staff development and assessment, teaching and classroom practices. These can enhance the opportunities for success for all dyslexic children and bring hope to parents.

In summery it is essential that despite the advances in scientific thinking and research that we do not lose sight of the individuals, their needs end their strengths. Brooks (2000, pg.19) summed this up very succinctly when he suggested "adolescents may begin to perceive the world as a place where their strengths rather than their weaknesses are spotlighted. If this shift in perception occurs, then when they are expected to assume the tasks of adulthood, they will do so with increased comfort, confidence end success".


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