Phonological dyslexia is the form of dyslexia which involves difficulty with the sounds of letters. It is a learning disability that falls under auditory processing and, in its more severe form, as Auditory Processing Disorder, or OPD. Words that are familiar can be read out as whole words but when new words are encountered, there is a difficulty in the sounding out of the letters or groups of letters. Though the exact cause in unknown, it may be due to auditory processing problems such as the inability to distinguish between subtle sound differences or hearing sounds at the wrong speed.
Young children who have phonological dyslexia may exhibit slow speaking speed development with particular problems in isolating the sounds in words and understanding rhyme. In their early school years, they may have difficulty in sounding out words and blending two or three letters to form a sound. There is no cure for phonological dyslexia but many dyslexics learn to read and write if given the right learning support. The earlier the intervention, the better the results. The latest research has shown that visual differences such as colored fonts and background can significantly improve reading ability.
Dyslexia is an umbrella term for reading disorders which can be divided into four types: phonological, surface, word-form or spelling and direct. Phonological dyslexia occurs when the person cannot link the sounds to the letters, or the auditory to the visual component. Surface dyslexia refers to problems with whole word recognition and is considered to be more of a visual problem than an auditory one as words can be sounded out phonetically. Sufferers of spelling dyslexia are able to read individual letters and are able to read the word in its entirety if given time, but they have difficulty with whole-word recognition and phonetics. Direct dyslexia refers to those who are able to read aloud well but have little or no comprehension.
The causes of dyslexia are basically two-fold. There is developmental dyslexia where the cause is biological and acquired dyslexia which is caused by brain trauma. The adult onset of dyslexia is primarily due to acquired dyslexia, while the biological or inherited form usually manifests itself in childhood. It is often inherited and tends to run in families. While the causes of phonological dyslexia are usually neurological, there are also hormone dysfunctions in the early stages of fetal development which are responsible for the condition in some cases. This type usually diminishes with age.
Both visual and auditory dyslexia are thought to be due to weaknesses in the thalamus, which is the part of the brain where the processing of visual and auditory information takes place. The difference between the two types of dyslexia arises because the weaknesses are not of the same type or degree. One person may have adequate visual skills but poor hearing skills and so suffer from auditory dyslexia. Another may have poorer visual than auditory skills and so suffer from visual dyslexia. The most common symptom ascribed to dyslexics occurs in this case when the words or letters are reversed whether the person is reading, writing or spelling.