Information on Dyslexia: Definition, Assessment, Interventions and Resources


Dyslexia is a syndrome: a collection of associated characteristics that vary in degree and from person to person. These characteristics encompass not only distinctive clusters of problems but sometimes also distinctive talents. Professor Tim Miles comments that dyslexia is typically characterised by ‘an unusual balance of skills’.

The syndrome of dyslexia is now widely recognised as being a specific learning disability of neurological origin that does not imply low intelligence or poor educational potential, and which is independent of race and social background.

Although dyslexia seems to be more prevalent amongst males than females, the exact ratio is unknown: the most commonly quoted figures are between 3:1 and 5:1. The evidence suggests that in at least two-thirds of cases, dyslexia has a genetic cause, but in some cases birth difficulties may play an aetiological role.

Dyslexia may overlap with related conditions such as dyspraxia, attention deficit disorder (with or without hyperactivity) and dysphasia. In childhood, its effects can be mis-attributed to emotional or behavioural disorder. By adulthood, many dyslexics will have developed sophisticated compensating strategies that may mask their difficulties.

The majority of experts concur that about 4% of the population are affected to a significant extent. This figure is based on the incidence of pupils who have received normal schooling and who do not have significant emotional, social or medical aetiology, but whose literacy development by the end of the primary school is more than 2 years behind levels which would be expected on the basis of chronological age and intelligence. However, perhaps as many as a further 6% of the population may be more mildly affected (e.g. in spelling).

The neurological bases of dyslexia are now well established and reflected in current definitions of the condition. For example, the International Dyslexia Association (formerly the Orton Dyslexia Society) published the following definition of dyslexia:

“Dyslexia is a neurologically-based, often familial disorder which interferes with the acquisition of language. Varying in the degrees of severity, it is manifested by difficulties in receptive and expressive language, including phonological processing, in reading, writing, spelling, handwriting and sometimes arithmetic. Dyslexia is not the result of lack of motivation, sensory impairment, inadequate instructional or environmental opportunities, but may occur together with these conditions. Although dyslexia is lifelong, individuals with dyslexia frequently respond successfully to timely and appropriate intervention” (Orton Dyslexia Society, 1994).

The biology of dyslexia has been investigated in a range of studies that have confirmed a difference in brain anatomy, organisation and functioning. Research has also shown that the effects of dyslexia are due – at least, in part – to heritable influences. The latest brain imaging techniques, as well as encephalographic recording of the electrical activity of the brain, and even post-mortem examination, all reveal a range of functional and structural cerebral anomalies of persons with dyslexia.

Although it is a disability, dyslexia is not a ‘disease’ nor can it be ‘cured’. Indeed, the neurological differences found in dyslexia may confer advantages for some individuals (e.g. in visual or perceptual skills), which may to some extent explain the apparent paradox that some individuals who have problems with elementary skills such as reading and writing can nevertheless be highly gifted in other areas.

The deficit model of dyslexia is now steadily giving way to one in which dyslexia is increasingly recognised as a difference in cognition and learning.

The following cognitive characteristics of dyslexia have been widely noted in connection with dyslexia:

  • A marked inefficiency in the working or short-term memory system
  • Inadequate phonological processing abilities
  • Difficulties with motor skills or co-ordination
  • A range of problems connected with visual processing

Main educational effects of dyslexia

Reading and perceptual difficulties

These can include:

  • early difficulties in acquiring phonic skills
  • a high proportion of errors in oral reading
  • difficulty in extracting the sense from written material without substantial rereading
  • slow reading speed
  • inaccurate reading, omission of words
  • frequent loss of the place when reading
  • an inability to skim through or scan over reading matter
  • a high degree of distractibility when reading
  • perceived distortion of text (words may seem to float off the page or run together)
  • a visually irritating glare from white paper or white-boards

Writing problems

These can include:

  • an intractable spelling problem, often concealed by the use of an automatic spell-checker
  • confusion of small words such as which/with
  • omission of words, especially when the writer is under pressure
  • awkward handwriting and/or slow writing speed
  • an unexpected difference between oral and written expression, with oral contributions being typically of a much higher quality than written accounts of the same subject matter in terms of structure, self expression and correct use of words.


Assessment of dyslexia, in the UK, is usually undertaken by a Chartered Educational Psychologist. S/he will look for a characteristic pattern of reading, perceptual and writing difficulties, as well as associated difficulties in such areas as: speech and language, numeracy, oral skills, attention and distractibility, social and emotional factors, organisation and under-achievement.

There is a considerable overlap between the characteristics and occurrence of developmental disorders, and one disorder can also mimic another. Considerable experience and expertise can be needed to make a differential diagnosis.

Further information on dyslexia screening is available on the Lucid Research area of this website. Lucid, developers of CoPs (Cognitive Profiling System), specialise in the development of computerised assessment systems for use in primary and secondary schools in the UK and overseas.


Multisensory methods of teaching are usually advocated for teaching dyslexic students. These integrate visual, aural, tactile and kinaesthetic modalities to consolidate the learning experience. Lessons must be very well structured, sequential and cumulative, and all skills and concepts must be thoroughly practised (overlearned) in order to counteract the memory problems of the dyslexic. Content generally needs to concentrate on phonic skills, as these are usually the weakest aspect in dyslexia.

The range of available products and materials for teaching and supporting children with dyslexia is steadily growing. Well-structured phonics-based multisensory teaching is still the fundamental requirement, especially for primary-aged dyslexics, but the approaches are much more flexible and more fun than the older drill methods.

IPS are running an innovative Dyslexia Summer School at Leysin American School, Switzerland, July/August 2005. For full details please click here



Further information on dyslexia screening is available on the Lucid Research area of this website. Lucid, developers of CoPs (Cognitive Profiling System), specialise in the development of computerised assessment systems for use in primary and secondary schools in the UK and overseas.


The following books are available from IPS Publications; prices are shown in £ sterling; an approximate exchange rate for US$ is £1 = US$1-50. Postage is £1 per book for UK domestic orders, and £2 per book for overseas surface postage. A publication ordering system is now available at IPS OnLine Store and any queries can be addressed to:

Understanding Dyslexia

Dyslexia: Biology, Cognition and Intervention – (Eds. C.Hulme and M. Snowling). Whurr, 1997. [A pretty comprehensive survey of current research; rather technical in places] £27-50

Dyslexia: a Practitioner’s Handbook – Gavin Reid. Wiley, 1998. [An excellent, up-to-date overview and compendium of resources.] £16

Dyslexia: the Pattern of Difficulties (2nd edition) – Tim Miles. Whurr, 1993. [A readable survey by one of the true pioneers in the field] £24-50

Specific Learning Difficulties (Dyslexia): Challenges and Responses – Peter Pumfrey and Rea Reason. Routledge, 1991. [The authority on evidence regarding research and practice on dyslexia; perhaps a little dated now but still a valuable resource] £20

Teaching Dyslexic Students

The Bangor Dyslexia Teaching System (3rd edition) – Elaine Miles. Whurr, 1997. [Excellent strategies for teaching, plus details of accompanying resources] £17

Day-to-day Dyslexia in the Classroom – Joy Pollock and Elizabeth Waller. Routledge, 1994. [A very practical guide for teachers] £13

Dealing with Dyslexia (2nd edition) – Pat Heaton and Patrick Winterson. Whurr, 1996. [A revised edition of a popular classroom text] £19-50

Maths for the Dyslexic: a Practical guide – Anne Henderson. David Fulton, 1998. [A new book of practical activities from one of the few experts on the subject of maths and dyslexia] £14

Overcoming Dyslexia: Skills into Action – Hilary Broomfield and Margaret Combley. Whurr, 1997. [A highly practical book using multisensory teaching for dyslexics of all ages] £22-50

The Phonics Handbook (2nd edition) – Sue Lloyd. Jolly Learning, 1994. [Especially suitable for use with younger children; lots of photocopiable activity sheets. Makes learning fun and not just for dyslexics]

Sound Linkage: An Integrated Pogramme for Overcoming Reading Difficulties – Peter Hatcher. Whurr, 1994. [Based on the author’s own research in Cumbria: a strongly phonological basis to reading development] £39-50

Teaching Reading and Spelling to Dyslexic Children – Margaret Walton. David Fulton, 1998. [A new compendium of exercises based on sound practice] £15

Computer support

There are many superb computer programs for learning and support of dyslexic children of all ages now available. The problem is to spot these amongst the hundreds advertised in the catalogues. To assist busy teachers, the British Dyslexia Association produces a series of inexpensive, up-to-date booklets that contain reviews of recommended software and give details of where these may be obtained and how the software can be used most effectively. The series includes:

  • Literacy Software – Jean Hutchins. BDA Booklet C14
  • Maths Support with ICT – Di Hillage and Jean Hutchins. BDA Booklet C15
  • IT for Dyslexic Adults: a Booklet for Beginners – Carol Kaufman. BDA Booklet C16
  • Study Skills with ICT – Carol Kaufman and Chris Singleton. BDA Booklet C17
  • Communication in Writing – Judith Stansfield. BDA Booklet C18

These booklets are available price £3.50 each (plus £1.50 p&p for up to 10 items) from the British Dyslexia Association, 98 London Road, Reading, England RG2 5AU. Tel. 0118 966 8271 Fax 0118 966 2677 E-mail:

The BDA also publishes a range of useful books and other literature on dyslexia, as well as a termly magazine called Dyslexia Contact. For further information contact the BDA at the address above.

Computer programs for use in schools and at home are available from REM, Great Western House, Langport, Somerset, England TA10 9YU. Tel. 01458 253636 Fax 01458 253646 E-mail: A free copy of their catalogue is available on request. Many programs can also be tried out by accessing their website:

Advice on computer hardware and software for older dyslexics is available from iANSYST, The White House, 72 Fen Road, Cambridge, England CB4 1UN. Tel. 01223 420101 Fax 01223 426644 E-mail: See also their website for further information: