How Is Dyslexia Defined?

There exists a range of definitions for dyslexia spanning the last century. This review focuses on those definitions from four influential organisations: The British Psychological Society (BPS), The World Federation of Neurology (WFN), British Dyslexia Association (BDA) and The International Dyslexia Association (IDA) who have all based their definitions on peer-review research and clinical evidence. The differences between these organisations result from what is included or excluded from their internally agreed understanding of developmental dyslexia. There are a number of preeminent definitions presently used and outlined below:

The World Federation of Neurology (1968) produced one of the earliest definitions of dyslexia and many authors (Elbeheri & Everatt 2009; Nicholson & Fawcett, 2005; Poole, 2003) still consider it the benchmark definition that remains pertinent to the modern researcher:

'A disorder in children who, despite conventional classroom experience, fail to attain the language skills of reading, writing and spelling, commensurate with their intellectual abilities.' (WFN, 1968, p. 21)

Dyslexia is thus complex to define, not all definitions of developmental dyslexia have widespread agreement amongst researchers and practitioners. If we choose to ignore Miles' (1995) concern that dyslexia is not definable, only describable, and support Miles' (1992) assertion that dyslexia is but a collection of actions with relevance to each other; dyslexia is a 'constitution of weakness that influences the way in which certain tasks are carried out' (Beaton, 2004, p. 10). Blindly accepting the term dyslexia as definable is indeed restricting but invariably it will continue to happen in practice. Educators and psychologists wishing to identify dyslexia in children are required to categorise the 'manifestations', 'asymbolia' and 'deficit in the acquisition of skill' (Miles, 1994, p. 205; Hermann, 1959, p. 17; Nicolson & Fawcett, 1990, p. 160). Reid-Lyon (1995) insists that a definition of dyslexia must be governed by a theoretical view whilst being supported by substantial research and clinical evidence.

The British Psychological Society (1999) defines dyslexia as:

'Dyslexia is evident when accurate and fluent reading and /or spelling develops very incompletely or with great difficulty. This focuses on literacy learning at the 'word level' and implies that the problem is severe and persistent despite appropriate learning opportunities. It provides the basis for a staged process of assessment through teaching'. (BPS, 1999, p. 5)

It is a widely used definition and reflects the same approach as found in the independent report by Rose (2009).

Whilst the WFN and BPS definitions can still be viewed as a clear, concise and uncluttered definitions, they may seem rudimentary in light of the BDA (2007) all encompassing effort below:

. `Dyslexia is a learning difficulty that primarily affects the skills involved in accurate and fluent word reading and spelling. . Characteristic features of dyslexia are difficulties in phonological awareness, verbal memory and verbal processing speed. . Dyslexia occurs across the range of intellectual abilities. . It is best thought of as a continuum, not a distinct category, and there are no clear cut-off points. . Co-occurring difficulties may be seen in aspects of language, motor co-ordination, mental calculation, concentration and personal organisation, but these are not, by themselves, markers of dyslexia. . A good indication of the severity and persistence of dyslexic difficulties can be gained by examining how the individual responds or has responded to well founded intervention` (Rose, 2009, p. 30).

In addition to these characteristics, the BDA acknowledges the visual and auditory processing difficulties that some individuals with dyslexia can experience, and points out that dyslexic readers can show a combination of abilities and difficulties that affect the learning process. Some also have strengths in other areas, such as design, problem solving, creative skills, interactive skills and oral skills.

This definition replaces the BDA's previous definition which was deficient in the explanation of affects of dyslexia beyond language and literacy skills, confusion over the implication of innate dyslexia and what in practice was 'specific intervention' (BDA, 2007, p. 1). The updated definition shown previously is in accordance with Sir Jim Rose's Report (2009, p30) with the addition of a paragraph to include further limitations to learning. Beyond the report supporting and explaining the bullet points, a marked change to the BDA's definition is that they now include 'strengths' of dyslexia; perhaps in recognition that although they advertise that dyslexia only accounts for one in ten of the population, a number of famous entrepreneurs are or thought to have been dyslexic (Logan, 2009).

The International Dyslexia Association (2002) defines dyslexia as:

"Dyslexia is a specific learning disability that is neurological in origin. It is characterized by difficulties with accurate and / or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge." (IDA, 2002, p. 1)

The International Dyslexia Association's definition is strongly grounded in developmental dyslexia, with the implication that due to phonological deficits the person is disadvantaged and will not develop the skill of spelling or reading at the expected rate.

Complementary to the BDA's definition, the overall ability of a dyslexic individual is implied to be equivalent with their peers. Uniquely, there is statement of 'effective classroom instruction' compared with the BDA`s assertion for 'intervention'; necessitating a holistic learning experience rather than segregation (BDA, 2007, p. 1; IDA, 2002, p. 1).

In summation, there remain issues surrounding the concept of developmental dyslexia, however these disagreements are in part due to what is included or excluded from the definition, what Miles (1994, p208) termed ' lumping and splitting'. The last decade has not diminished the appetite to modify the definition of dyslexia, the question remains; is it solely a 'reading disability'?

Reid -Lyon (1995, p. 1) endeavoured to identify dyslexia in isolation from 'its common association with other learning disabilities' and the Welsh Assembly Government (2012, p. 6) want to extend this research by proposing further study into what constitutes 'pure' phonological dyslexia. Conversely, in England and Scotland dyslexia is still considered to have 'co-occurring' factors but alarmingly the Scottish Government state on their website that dyslexia is a 'neurological disorder', a 'syndrome' (Rose, 2009; The Scottish Government, 2008). Perhaps the Scottish Government are unaware that this assertion of dyslexia as a 'syndrome' is a replication of Miles' study from 1974.

One may jest that terminology for dyslexia changes depending upon what is vogue, which simply reflects the multitude of avenues of research surrounding the complex neurological factors that influence a child's phonological awareness.