It’s time for experts to come to an agreement about how to define dyslexia. (E.Va/Shutterstock)

BIRMINGHAM, England — For over a century, educators, psychologists, and researchers have disagreed about what exactly dyslexia is. Some have called it “word blindness,” others view it as a problem processing speech, and some consider it a reading disorder tied to intelligence. This confusion hasn’t just been academic; it has created real problems for parents, teachers, and individuals with dyslexia.

In a study published in the Journal of Child Psychology and Psychiatry, this long-standing debate may finally be resolved. Using a method called a Delphi study, researchers brought together dyslexia experts from multiple countries and disciplines to build a unified definition everyone could agree on. Researchers from the University of Birmingham planned to cut through decades of disagreement and establish a clear understanding of dyslexia.

Why a universal definition matters

“There has not been a new attempt to define dyslexia since the Rose Review in 2009,” explains lead study author Julia Carroll from the University of Birmingham, in a statement. “Despite the Rose definition significantly influencing practice, it has gathered criticism over the last 15 years and has not been universally accepted

This lack of consistency has created a kind of lottery for kids with dyslexia. Depending on where they live, they might get an accurate diagnosis and appropriate help, or they might fall through the cracks entirely. It also affects how we understand how common dyslexia is, with estimates ranging from 5% to 20% of the population based on different criteria.

“The process for identifying learning needs and interventions can vary massively from place to place,” adds Carroll. “Adopting a universal definition for dyslexia is the first step to improving support for children experiencing the challenges of dyslexia.”

How dyslexia has been defined over time

Over the years, dyslexia has been defined in dramatically different ways. In 1968, the World Federation of Neurology emphasized a gap between reading skills and intelligence. By 2002, the International Dyslexia Association was highlighting brain-based origins and problems with processing speech sounds. The Rose report in 2009 described dyslexia as affecting people across all intelligence levels and existing on a spectrum rather than as a yes-or-no condition.

Meanwhile, medical manuals like DSM-5 and ICD-11 avoid the term “dyslexia” altogether, preferring phrases like “specific learning disorder in reading.” This only adds another layer of confusion.

The new consensus definition takes a more comprehensive approach. Rather than pinning dyslexia on a single cause, it acknowledges that multiple factors contribute to the condition. While difficulty processing speech sounds remains the most common issue in dyslexia, the experts agree it’s not the whole story. Working memory (our ability to hold and work with information in our minds), processing speed, and the ability to recognize and remember letter patterns can also play important roles.

An in-depth understanding of dyslexia

The panel also highlighted that dyslexia often occurs alongside other developmental conditions, such as language disorders, ADHD, coordination difficulties, and math difficulties. This insight, often underemphasized in previous definitions, is crucial for providing appropriate support.

Dyslexia also looks different across languages and throughout a person’s life. In languages with more predictable spelling than English, people with dyslexia might read accurately but still struggle with reading speed. As people with dyslexia grow older, their challenges often shift from basic reading to problems with reading speed, fluency, and spelling.

The experts also tackled some common misconceptions. Despite claims that dyslexia gives advantages in creativity or visual thinking, research hasn’t consistently shown these benefits at a group level. They also clarified that visual stress, sensitivity to high-contrast patterns like black text on white backgrounds, is separate from dyslexia, though it can make reading even harder for those affected.

The new definition of dyslexia

Based on the 42 statements that received at least 80% agreement, the researchers created a comprehensive definition of dyslexia that includes several key components:

• Dyslexia is a set of processing difficulties that affect reading and spelling.
• It involves literacy skills that are weak compared to age, teaching quality, and other abilities.
• Problems with reading speed and spelling are key markers across all languages.
• It exists on a continuum of severity rather than being a yes-or-no condition.
• It results from multiple genetic and environmental factors.
• It can affect other skills like math and language learning.
• It frequently occurs alongside other developmental conditions.

“A definition of a learning disorder such as dyslexia should allow researchers and practitioners to consistently establish what should or should not be considered ‘dyslexia,’” adds Carroll. “Our new definition retains the idea of difficulties with reading and spelling relative to age, ability, or educational expectations. However, it is less focused on English speakers and children. We highlight that processing speech sounds has a causal link to dyslexia, but that other factors also play an important role in explaining why it can look different in different people.”

The research team didn’t stop at defining dyslexia. In a companion study published in the Dyslexia Journal, they outlined a standardized four-stage assessment process:

1. Consider other factors: Rule out other potential causes of reading, spelling, or writing difficulties.
2. Provide early intervention: Gather more information and act quickly to support struggling learners.
3. Monitor progress: Observe and evaluate how the child responds to intervention.
4. Comprehensive assessment: If progress stalls refer for specialist assessment.

This standardized approach could help address the current situation where assessment and support vary dramatically by location.

Moving forward

Even Professor Elliott, who has previously questioned the value of diagnosing dyslexia, participated in the Delphi panel. While the definition doesn’t resolve every controversy, like whether dyslexia should be diagnosed in people with intellectual disabilities, it represents an unprecedented agreement among experts with diverse viewpoints.

For people with dyslexia, this new definition validates their experiences while acknowledging that dyslexia is complex and varies from person to person. It moves beyond overly simple explanations and recognizes that dyslexia affects individuals differently depending on their language, age, and personal circumstances.

“Dyslexia is a complex learning disorder that can look different from person to person. It can have lasting impacts on education and then on working life if not identified and addressed properly,” says Carroll. “By not having a universal process to identify and support people with dyslexia, we are letting down so many of our children and young people. If the government is serious about improving SEND provision in schools, then updating and standardizing the definition and assessment for dyslexia should be a priority.”

After more than a century of competing definitions, dyslexia research has finally reached a consensus that combines scientific evidence with real-world expertise. This achievement could transform how we identify, understand, and support millions of people worldwide with this common but often misunderstood learning difference.