Other Definitions

It has been said that human knowledge progresses through three stages; (1) the unanimity of the ignorant, (2) the disagreement of the enquiring and (3) the unanimity of the wise. Regarding current knowledge of dyslexia, the world is certainly in the second stage. A lot is known, but there is much that is still unknown.

While there is, at present, no universally accepted definition of dyslexia, it is probable that no single definition will ever satisfy all needs.  This, however, should not prevent us from recognising and supporting children who have specific learning difficulties.

All children learn in different ways and can be said to have different learning styles.  The task of learning literacy skills is a complex one and difficulties will arise for a significant number of children for a variety of reasons.

A definition such as that given in the Task Force and Task Group Reports, which is broad in conceptualisation describing dyslexia through a statement of typical characteristics, is the most useful starting point for teachers.

It seems unlikely that there is any one symptom or sign which will qualitatively distinguish dyslexics from non-dyslexics. Therefore, it is not possible in any simple way to divide the population into those who are dyslexic and those who are not. This is why it is useful to consider dyslexia in descriptive terms along a continuum.

However, over the years, many individuals and institutions have proposed a variety of definitions for a variety of reasons. In some cases a definition is designed to define research questions. In other circumstances, a definition may be used to establish a policy or to facilitate diagnosis for access to kinds of provision. Some definitions are used to highlight theorised causes of dyslexia or to support the hypothesis for an intervention, while still others are descriptions for the use of practitioners. The differences exhibit a variety of ways of constructing definitions and of purposes for doing so. 


1. Examples from government sources:

- Special Education Review Committee Report (Ireland), 1993:

Specific learning disability is a term used for the purposes of this Report to describe impairments in specific areas such as reading, writing, spelling and arithmetical notation, the primary cause of which is not attributable to assessed ability being below the average range, to defective sight or hearing, emotional factors, a physical condition or to any extrinsic adverse circumstances.

- The Code of Practice on the Identification and Assessment of Special Educational Needs (Northern Ireland), 1996:

Some children may have significant difficulties in reading, writing, spelling or manipulating numbers, which is not typical of their general level of performance, especially in other areas of the curriculum. They may gain some skills in some subjects quickly and demonstrate a high level of ability orally, yet may encounter sustained difficulty in gaining literacy or numeracy skills. Such children can become severely frustrated and may also have emotional and/or behavioural difficulties.

- The Individuals with Disabilities Education Act (USA), 1997:

The term ‘specific learning disability’ means a disorder in one or more of the basic psychological processes involved in understanding and using language, spoken or written, which disorder may manifest in imperfect ability to listen, think, speak, read, write, spell or do mathematical calculations. Such term includes such conditions as perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia. Such term does not include a learning problem that is primarily the result of visual, hearing, or motor disabilities, of mental retardation, of emotional disturbance, or of environmental, cultural, or economic disadvantage.

- National Institute of Child Health and Development (USA), 1994:

Dyslexia is a specific learning disability that is neurobiological 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 consequence may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.

- ICD-10 Diagnostic Criteria for the Diagnosis of Specific Reading Disorder (W.H.O. Diagnostic Criteria for Research), 1992:

A score on reading accuracy and/or comprehension that is at least 2 standard errors of prediction below the level expected on the basis of the child’s chronological age and general intelligence, with both reading skills and IQ assessed on an individually administered test standardized for the child’s culture and educational system.

- The Code of Practice in Education (Hong Kong Equal Opportunity Commission),  2001:

Developmental dyslexia (SpLD) refers to a child’s severe and persistent difficulty in the acquisition of reading (word recognition) and dictation /spelling skills which is not commensurate with his/her overall ability to respond to the “thinking, reasoning and understanding” aspects of the curriculum. SpLD has a neurological basis, and is not caused by a lack of learning opportunity, severe emotional or behavioural disturbance or handicapping conditions such as intellectual or sensory/motor impairment. Problems with memory, organisation, handwriting, arithmetic, speech and language and attention deficits can co-occur.

- Committee of the Health Council of the Netherlands, 1997:

Dyslexia is present when the automatisation of word identification (reading) and/or word spelling does not develop or does so very incompletely or with great difficulty.

2. Examples from dyslexia and other organisations:

- British Dyslexia Association, 2001:

Dyslexia is a combination of abilities and difficulties that affect 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.

- The Adult Dyslexia Organisation (UK), 1999:

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 and 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 as problem solving which can tap resources which lead to more originality and creativity.

- International Dyslexia Association (USA), 1996:

 Dyslexia is a neurologically-based, familial disorder which interferes with the acquisition and processing of linguistic information, varying in degrees of severity. It is manifested by difficulties in receptive and expressive language, including phonological processing, reading, writing, spelling and sometimes arithmetic. Dyslexia may occur concomitantly with other limiting factors such as lack of motivation, sensory impairment or inadequate instructional or environmental opportunities, but it is not the result of these conditions. Although Dyslexia is life-long, individuals with Dyslexia successfully respond to timely and appropriate intervention.

- British Psychological Society, Division of Educational and Child Psychology, 1999:

Dyslexia is evident when accurate and fluent word 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.

3. Examples from individuals:

- Reid, 2002:

Dyslexia is a processing difference experienced by people of all ages, often characterised by difficulties in literacy; it can affect other cognitive areas such as memory, speed of processing, time management, co-ordination and directional aspects. There may be visual and phonological difficulties and there is usually some discrepancy in performances in different areas of learning. It is important that the individual difference and learning styles are acknowledged since these will affect outcomes of assessment and learning. It is also important to consider the learning and work context as the nature of the difficulties associated with dyslexia may be more pronounced in some learning situations.

- Smythe, 2000:

Dyslexia is a difficulty with the acquisition of reading, writing and spelling which may be caused by a combination of phonological, visual and auditory processing deficits. Word retrieval and speed of processing difficulties may also be present. The manifestation of dyslexia in any individual will depend upon not only individual cognitive differences, but also the language used.