Dyslexia is widely regarded as a condition that affects how individuals acquire reading and writing skills. However, it is much more complex than that, leading researchers to devise definitions to help clarify these complexities. For many years, the UK has adhered to the Rose Definition and the British Dyslexia Association’s supplementary definition. Nevertheless, significant advances in research have been made since these definitions were first published; therefore, we welcome the new Delphi Definition of dyslexia with excitement, developed in collaboration with SASC.  This is the first time we have seen a universally agreed definition, as all previous definitions have been the subject of significant debate among researchers.

These scientific definitions can sometimes be challenging to grasp, so let’s examine each part and its meaning.

Delphi Definition of Dyslexia

Carroll, J., Holden, C., Kirby, P., Snowling, M. J., & Thompson, P.A. (2024).

Nature

“The nature and developmental trajectory of dyslexia depend on multiple genetic and environmental influences.”

It’s a complex interplay of genetics and environmental factors that contribute to dyslexia, but, simply put, it runs in families. There is a strong genetic link, though environmental influences also play a significant role in its development and manifestation in individuals. For instance, a family member may struggle more with maths than with spelling, but it’s the same genes at work. Additionally, early childhood health and experiences will affect how the brain is ‘wired’ (for ease of explanation).

Manifestation

“Dyslexia is a set of processing difficulties that affect the acquisition of reading and spelling.”

It is a different way of processing information and impacts the part of the brain responsible for learning how to read and write.

“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.”

Words in any language consist of individual sounds. These are called phonemes. Each phoneme (sound) is represented with a graphic symbol or grapheme (alphabet letters).

To read and write, our brain needs to be able to identify the target sounds within the word (phonological awareness) and connect them with the appropriate symbols. This is known as phonological processing. When a person has dyslexia, one or more of the processes involved is affected, whether it is the speed at which the information is accessed, the ability to recall and match the correct symbol/s, or a combination of these.

“Working memory, processing speed and orthographic skills can contribute to the impact of dyslexia.”

Working memory is the ability to temporarily retain information while performing tasks that require several steps. Skills related to working memory are essential for many daily activities.

Orthographic skills involve recognising, organising, and recalling letter patterns and spelling rules in a language. Children who receive focused phonics support at school may grasp sounds well but struggle to remember how letters are shaped and the correct order of letters needed to produce a sound. This challenge is referred to as orthographic processing difficulties.

Impact

“In dyslexia, some or all aspects of literacy attainment are weak in relation to age, standard teaching and instruction, and level of other attainments.”

Every child develops at their own pace, but after two years of continuous education, one would expect them to write clear and somewhat longer sentences independently. Additionally, one would hope for fluent reading and a good understanding of age-appropriate texts. When a child has dyslexia their reading and writing skills do not align with their age or the time they have spent in school.

“Across languages and age groups, difficulties in reading and spelling fluency are a crucial marker of dyslexia.”

While some languages are more phonological than others, the processing difficulties observed in dyslexia (e.g. working memory or processing speed) can occur in any language if a child is multilingual. 

Variance and co-occurrence

"Dyslexic difficulties exist on a continuum and can be experienced to various degrees of severity."

Dyslexia can range from mild to severe difficulties. Although there are common traits, its impact on individuals varies from one person to another.

"Dyslexia can affect the acquisition of other skills, such as mathematics, reading comprehension or learning another language."

Dyslexia affects more than just reading and writing. It can impact academic learning and various aspects of daily life and education, including processing incoming information, following written instructions, sequencing and planning, and making decisions. Difficulties with mathematics often involve challenges in learning times tables and solving word problems.

"Dyslexia frequently co-occurs with one or more other developmental difficulties, including developmental language disorder, dyscalculia, ADHD, and developmental coordination disorder."

The link below will take you to the glossary resource. Here, you can learn what each acronym for the co-occurring conditions means.

In summary

The primary function of a definition is to provide assessors with a set of criteria to help them identify the condition. Previous definitions highlighted that individuals with dyslexia often display a set of strengths in other areas, such as creative arts or problem-solving skills. Although it is not included in the Delphi Definition, the SASC guidelines for report writing emphasise the importance of assessors adopting a holistic view of strengths and difficulties. A diagnostic assessment will, therefore, offer parents, carers, and teachers a greater understanding of how the child processes information and learns best.

Aside from academic intervention, parents, carers, and teachers must help children understand how their brains work. This self-awareness is the first step towards achieving one’s dreams. Indeed, dyslexia can have debilitating effects, but it is never an excuse to avoid doing your best or to shy away from challenges. With the right tools and support, many dyslexic individuals achieve remarkable success. Nevertheless, success can only be attained through hard work and determination, regardless of whether you have dyslexia or not.

Resources

Click on the link below to read the full article which is now fully peer-reviewed and published in The Journal of Psychology and Psychiatry.

Toward a consensus on dyslexia: findings from a Delphi study

Julia M. Carroll, Caroline Holden, Philip Kirby, Paul A. Thompson, Margaret J. Snowling, 

the Dyslexia Delphi Panel