What is Dyslexia?

In 2025, a new definition of dyslexia was agreed, called the Delphi Definition. This definition was created as a result of research led by Professor Julia Carroll, Professor of Psychology in Education at the University of Birmingham. This definition states that dyslexia is a set of processing difficulties that affect the acquisition of reading and spelling.

These processing difficulties are typically phonological processing difficulties, which include:

• Phonological awareness

• Phonological short-term memory

• Phonological processing speed

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Phonological awareness

Phonological awareness is the ability to accurately identify, discriminate between and

manipulate the separate units of sounds in words, known as ‘phonemes'. It can be measured using a wide range of speech sound tasks, such as identifying, segmenting, or blending syllables within words, as well as being able to delete parts of words. For example, knowing that the word 'rainbow' without 'bow' is 'rain'. Phonological awareness is strongly related to reading and spelling. In the well regarded book 'Understanding and Supporting Children with Literacy Difficulties' by Dr Valerie Muter, it states that phonological awareness helps develop reading development, but reading also helps develop phonological awareness skills.

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Phonological short term memory

Phonological short-term memory is the ability to identify accurately, retain briefly, and repeat sequences of speech sounds. This part of the memory provides very brief storage of auditory information , although it is useful to know that the length of time that this information can be stored can be increased through rehearsal processes (such as repeating a name over and over again). Phonological memory influences a person's ability to learn new written and spoken vocabulary.

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Phonological processing speed

Phonological processing speed is ability to retrieve accurately well-known phonological responses (e.g. names of letters, numbers, objects, colours) fluently from long-term memory in response to a visual stimulus (e.g. letters or digits). It is linked to reading as successful reading depends on looking at written words and accurately and quickly mapping them to the correct pronunciation.

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People with dyslexia may have difficulties in one or more areas of phonological processing, affecting the accuracy and/or fluency of their reading and spelling.

If you book a dyslexia assessment for primary or secondary school children with Bucks Dyslexia, all these three areas are assessed.