Redefining Dyslexia by Consensus

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British special educators have adopted a new and broader definition of dyslexia, based on the consensus recommendations of educators, psychologists, and dyslexic adults.

The new definition adopted by PATOSS¹ (the professional association of teachers of students with specific learning difficulties) is as follows:

• Dyslexia is primarily a set of processing difficulties that affect the acquisition of reading and spelling.
• In dyslexia, some or all aspects of literacy attainment are weak in relation to age, standard teaching and instruction, and level of other attainments.
•  Across languages and age groups, difficulties in reading and spelling fluency are a key marker of dyslexia.
• The nature and developmental trajectory of dyslexia depends on multiple genetic and environmental influences.
•  Dyslexic difficulties exist on a continuum and can be experienced to various degrees of severity.
• Dyslexia can affect the acquisition of other skills, such as mathematics, reading comprehension or learning another language.
• The most commonly observed cognitive impairment in dyslexia is a difficulty in phonological processing (i.e. in phonological awareness, phonological processing speed or phonological memory). However, phonological difficulties do not fully explain the variability that is observed.
• Working memory, orthographic skills and processing speed problems can contribute to the impact of dyslexia and therefore should be assessed.
• Dyslexia frequently co-occurs with one or more other developmental difficulty, including developmental language disorder, dyscalculia, ADHD, and developmental coordination disorder.

The new definition is the outgrowth of a Delphi study conducted among a panel of dyslexia experts, including academics, specialist teachers, educational psychologists, and individuals with dyslexia.² Repeated surveys resulted in greater than 80% consensus for 42 statements about dyslexia. The new definition draws from the statements most relevant to dyslexia assessment.

The consensus-based definition aims to resolve disputes about defining dyslexia that have led to problems and confusion for dyslexic individuals, their families, and the professionals who support them. In recognizing that dyslexic difficulties exist on a continuum with varying severity levels, the new definition addresses the limitations of previous definitions. Older definitions often excluded individuals whose difficulties were not deemed severe enough or whose symptoms manifested in unexpected ways. Instead of focusing on specific skill levels, the new definition emphasizes the underlying processing difficulties.

Additionally, while the importance of phonological processing is highlighted, the new definition acknowledges multiple causes and learning challenges. By shifting the focus to the key indicator of reading and spelling fluency, the definition is less tied to problems specific to English spelling conventions, and more inclusive of older students and adults. The inclusion of other commonly coexisting challenges promotes a holistic view of each person’s learning profile, reducing the likelihood of miscategorization during the evaluation.

1. Introducing a new definition of dyslexia, News 13/05, PATOSS-dyslexia.org, Retrieved 28 May 2024. ↩︎
2. Carroll, Julia, et al. “Towards a Consensus on Dyslexia: Findings from a Delphi Study.” OSF Preprints, 3 May 2024. Web.; Kirby, Philip, et al. “Towards a Consensus for Dyslexia Practice: Findings of a Delphi Study on Assessment and Identification.” EdArXiv, 2 May 2024. Web. (A Delphi study is a systematic process that uses multiple rounds of questionnaires to gather the opinions of experts and develop a consensus on a specific topic.) ↩︎