Current research indicates that the vast majority of children with dyslexia have phonological core deficits. The severity of the phonological deficits varies across individuals, and children with these deficits have been shown to make significantly less progress in basic word reading skills compared to children with equivalent IQs. Without direct instruction in phonemic awareness and sound-symbol correspondences, these children generally fail to attain adequate reading levels. The major components of phonological deficits involve phonemic awareness, sound-symbol relations, and storage and retrieval of phonological information in memory. Problems with phonemic awareness are most prevalent and can coexist with difficulties in storage and retrieval among children with dyslexia who have phonological deficits.
Phonemic awareness refers to one's understanding of and access to the sound structure of language.
For example, children with dyslexia have difficulty segmenting words into individual syllables or phonemes and have trouble blending speech sounds into words. Storage of phonological information during reading involves creating a sound-based representation of written words in working memory. Deficits in the storage of phonological information result in faulty representations in memory that lead to inaccurate applications of sound rules during reading tasks. Retrieval of phonological information from long-term memory refers to how the child remembers pronunciations of letters, word segments, or entire words. Children with dyslexia may have difficulty in this area, which leads to slow and inaccurate recall of phonological codes from memory.