The IDA fact sheet titled Dyslexia Assessment: What is it and how can it help? states "the problems associated with dyslexia are language-based, not related to cognitive skills or intelligence. Phonological processing problems are the principal cause of dyslexia. Phonological processing refers to the ability to analyze speech or spoken language, from identifying individual words, to word parts or syllables, and then into the smallest parts called phonemes or speech sounds."
So why do dyslexic people often have letter and word reversals?
In order to read and write fluently, a person must have the ability to:
And that is all before we even consider comprehension!
The New Jersey Department of Education, along with many other states, has adopted the International Dyslexia Association's (IDA) definition of Dyslexia.
"Dyslexia is a specific learning disability that is neurobiological in origin. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.”
Here is a great video from Reading Rockets that explains what phonological awareness means. The graphic below is also from Reading Rockets.
Through an intense, structured literacy approach which utilizes responsive teaching methods. In other words, the teacher must consistently monitor the student's understanding to know when to move on and what to cover next. Not all children are developmentally ready for the same instruction at the same time.