This is one of the starting points for ensuring that the intervention is correctly directed to your needs.
There are 3 underlying causes for difficulties in literacy, they interact with each other and then there a number of overlaying difficulties which add to them.
The 3 underlying difficulties;
1 Phonological Processing.
2 Visual Integration and Processing
3 Memory
The visual integration difficulties will be picked up by timed rapid naming activities and various decoding or picking out identical shapes activities.
When visual integration is causing the difficulties the dyslexic is often less badly affected in the early stages of school but much more noticeably affected latter in their studies.
Phonological processing is tested for by activities such as first sound matching, blending sounds, segmenting words.
Where this is the main cause of the student's difficulties, you will notice a great deal of difficulties in the early staged of reading, but if the student is taught to use phonics, they will make progress and will become fairly proficient later on and appear to be less badly affected later in their studies.
Memory will affect the student's ability right the way through the studies. There are many different memories and different memory difficulties will affect the student differently and not all will be possible to pick up easily by just observing the student.
Short term memory is the one that many people are aware of, this is often tested for by using a digit span and a letter span test, where you see how many letters or digits the student can remember and recall if they are presented at one second intervals.
However we also test for the phonological store, which is when the letters, sounds or digits are presented quite quickly, much faster than one per second. This is the immediate store that you use when someone speaks to you and you hear a word, then another and while that is happening you have to access your memory for the word so that you can understand what they are saying.
You may also test a student for memory for stories or episodic memory, this gives us a clue as to how they remember things they hear in prose. Can they remember it. This will be an underlying ability that they need to use when doing a comprehension exercise or listening to the lesson and then being able to understand it. Episodic memory is the memory for episodes in your life.
They may remember, but not be able to use the information. The use of the information requires working memory, this is the memory, in which, we manipulate information. We need this for understanding similes and metaphor, we use it while doing maths in your head, we use it for working out what the science means.
We also have Semantic Memory, which is our memory for facts.
Adding to a student's difficulties reading could be difficulties with binocular vision, focusing on the page, in ability to seccade, this is a jump the eyes make to take in the next word on the page. It is not automatic and has to be learned. Some children take longer to learn it than others. When they are struggling with this you will some some noticeable features in the way that they read.
As assessors we test for this by getting the student to read a passage, timed with us making notes on what they actually read compared to what is in front of them.
Phonological processing difficulties can be limited to segmenting or blending or spread across both of these skills.